diff --git a/src/blockstore/blockstore_flush.cpp b/src/blockstore/blockstore_flush.cpp
index ddcf4775..03abd160 100644
--- a/src/blockstore/blockstore_flush.cpp
+++ b/src/blockstore/blockstore_flush.cpp
@@ -24,6 +24,11 @@ journal_flusher_t::journal_flusher_t(blockstore_impl_t *bs)
     {
         co[i].co_id = i;
         co[i].bs = bs;
+        if (bs->dsk.csum_block_size > bs->dsk.bitmap_granularity)
+        {
+            co[i].new_csums = (uint8_t*)malloc_or_die(bs->dsk.data_block_size / bs->dsk.csum_block_size * (bs->dsk.data_csum_type & 0xFF));
+            co[i].new_bmp = (uint8_t*)malloc_or_die(bs->dsk.clean_entry_bitmap_size);
+        }
         co[i].flusher = this;
     }
 }
@@ -54,6 +59,16 @@ journal_flusher_t::~journal_flusher_t()
 
 journal_flusher_co::~journal_flusher_co()
 {
+    if (new_csums)
+    {
+        free(new_csums);
+        new_csums = NULL;
+    }
+    if (new_bmp)
+    {
+        free(new_bmp);
+        new_bmp = NULL;
+    }
     free_buffers();
 }
 
@@ -151,14 +166,6 @@ bool journal_flusher_co::loop()
     else if (wait_state == 14) goto resume_14;
     else if (wait_state == 15) goto resume_15;
     else if (wait_state == 16) goto resume_16;
-    else if (wait_state == 17) goto resume_17;
-    else if (wait_state == 18) goto resume_18;
-    else if (wait_state == 19) goto resume_19;
-    else if (wait_state == 20) goto resume_20;
-    else if (wait_state == 21) goto resume_21;
-    else if (wait_state == 22) goto resume_22;
-    else if (wait_state == 23) goto resume_23;
-    else if (wait_state == 24) goto resume_24;
 resume_0:
     wait_state = 0;
     wait_count = 0;
@@ -168,10 +175,10 @@ resume_0:
         (!bs->dsk.disable_journal_fsync || !bs->dsk.disable_meta_fsync))
     {
         flusher->active_flushers++;
-resume_21:
-resume_22:
-        res = fsync_buffer(21);
-        if (!res)
+resume_14:
+resume_15:
+resume_16:
+        if (!fsync_buffer(14))
         {
             return false;
         }
@@ -180,18 +187,6 @@ resume_22:
     }
     if (res == ENOENT)
     {
-        if (co_id == 0 && flusher->force_start > 0)
-        {
-            flusher->active_flushers++;
-resume_16:
-resume_17:
-resume_18:
-resume_19:
-resume_20:
-            if (!trim_lsn(16))
-                return false;
-            flusher->active_flushers--;
-        }
         cur_oid = {};
         wait_state = 0;
         return true;
@@ -206,35 +201,37 @@ resume_20:
         }
     }
 resume_1:
+    wait_state = 1;
     should_repeat = false;
-    cur_obj = bs->heap->lock_and_read_entry(cur_oid, copy_id);
+    cur_obj = bs->heap->lock_and_read_entry(cur_oid);
     if (!cur_obj)
     {
         // Object does not exist
         goto resume_0;
     }
-    cur_version = cur_obj->get_writes()->version;
-    // Find the range to compact
-    compact_lsn = bs->heap->get_fsynced_lsn();
-    bs->heap->get_compact_range(cur_obj, compact_lsn, &begin_wr, &end_wr);
-    if (!begin_wr)
-    {
-        // Nothing to flush
-        bs->heap->unlock_entry(cur_oid, copy_id);
-        goto resume_0;
-    }
-    assert(!end_wr->next() && end_wr->entry_type == (BS_HEAP_BIG_WRITE|BS_HEAP_STABLE));
-    clean_loc = end_wr->big_location(bs->heap);
-    if (bs->log_level > 10)
-        printf("Compacting %jx:%jx l%ju .. l%ju (last l%ju)\n", cur_oid.inode, cur_oid.stripe, end_wr->lsn, begin_wr->lsn, compact_lsn);
-    flusher->active_flushers++;
     // Scan versions to flush
     free_buffers();
     copy_count = 0;
-    for (auto wr = begin_wr; wr != end_wr; wr = wr->next())
+    fsynced_lsn = bs->heap->get_fsynced_lsn();
+    compact_info = bs->heap->iterate_compaction(cur_obj, fsynced_lsn, flusher->force_start, [&](heap_entry_t *wr)
     {
-        bs->prepare_read(read_vec, cur_obj, wr, 0, bs->dsk.data_block_size);
-        copy_count++;
+        if (wr->type() == BS_HEAP_SMALL_WRITE ||
+            wr->type() == BS_HEAP_INTENT_WRITE && bs->dsk.csum_block_size > bs->dsk.bitmap_granularity)
+        {
+            bs->prepare_read(read_vec, cur_obj, wr, 0, bs->dsk.data_block_size);
+            copy_count++;
+        }
+    });
+    if (!compact_info.compact_lsn)
+    {
+        // Flushing is aborted
+        bs->heap->unlock_entry(cur_oid);
+        goto resume_0;
+    }
+    flusher->active_flushers++;
+    if (bs->log_level > 10)
+    {
+        printf("Compacting %jx:%jx l%ju .. l%ju\n", cur_oid.inode, cur_oid.stripe, compact_info.clean_lsn, compact_info.compact_lsn);
     }
     overwrite_start = overwrite_end = 0;
     if (read_vec.size() > 0)
@@ -254,7 +251,6 @@ resume_1:
     }
     // Read buffered data
     cur_obj = NULL;
-    begin_wr = end_wr = NULL;
 resume_2:
 resume_3:
     if (!read_buffered(2))
@@ -272,29 +268,45 @@ resume_3:
         flusher->wanting_meta_fsync--;
     }
     res = check_and_punch_checksums();
-    if (res == EBUSY)
-    {
-resume_4:
-resume_5:
-        if (!write_meta_block(4))
-        {
-            return false;
-        }
-resume_6:
-resume_7:
-resume_8:
-        if (!fsync_meta(6))
-        {
-            return false;
-        }
-        res = 0;
-    }
-    else if (res == ENOENT || res == EDOM)
+    if (res == ENOENT || res == EDOM)
     {
         // Abort compaction
         flusher->active_flushers--;
         goto resume_0;
     }
+    if (res == EBUSY)
+    {
+resume_4:
+        modified_block = UINT32_MAX;
+        res = bs->heap->add_punch_holes(cur_obj, compact_info.clean_lsn, compact_info.clean_version, new_bmp, new_csums, &modified_block);
+        if (res == ENOENT)
+        {
+            // Abort compaction
+            flusher->active_flushers--;
+            goto resume_0;
+        }
+        if (res == EAGAIN)
+        {
+            // Retry, block is busy
+            wait_state = 4;
+            return false;
+        }
+        assert(res == 0);
+resume_5:
+resume_6:
+        if (!write_meta_block(5))
+        {
+            return false;
+        }
+resume_7:
+resume_8:
+resume_9:
+        if (!fsync_meta(7))
+        {
+            return false;
+        }
+        res = 0;
+    }
     assert(res == 0);
     // Submit data writes
     for (i = 0; i < read_vec.size(); i++)
@@ -304,26 +316,26 @@ resume_8:
             (read_vec[i].copy_flags & COPY_BUF_PADDED)) // FIXME Shit, simplify these flags
         {
             assert(read_vec[i].buf);
-            await_sqe(9);
+            await_sqe(10);
             data->iov = (struct iovec){ read_vec[i].buf + (read_vec[i].copy_flags & COPY_BUF_PADDED
                 ? read_vec[i].offset - read_vec[i].disk_offset : 0), (size_t)read_vec[i].len };
             data->callback = simple_callback_w;
-            io_uring_prep_writev(sqe, bs->dsk.data_fd, &data->iov, 1, bs->dsk.data_offset + clean_loc + read_vec[i].offset);
+            io_uring_prep_writev(sqe, bs->dsk.data_fd, &data->iov, 1, bs->dsk.data_offset + compact_info.clean_loc + read_vec[i].offset);
             wait_count++;
         }
     }
-resume_10:
+resume_11:
     if (wait_count > 0)
     {
-        wait_state = 10;
+        wait_state = 11;
         return false;
     }
     // Lock is only needed to prevent freeing the big_write because we overwrite it...
-    bs->heap->unlock_entry(cur_oid, copy_id);
+    bs->heap->unlock_entry(cur_oid);
     // Mark the object compacted, but don't free and remove small_writes
     // We'll free and remove them only when trimming
     // The only thing we modify here are big_write block checksums if >4k block is used
-    cur_obj = bs->heap->read_entry(cur_oid, &modified_block);
+    cur_obj = bs->heap->read_entry(cur_oid);
     if (!cur_obj)
     {
         // Abort compaction
@@ -334,40 +346,20 @@ resume_10:
         // Abort compaction
         goto resume_0;
     }
-    if (read_to_fill_incomplete)
-    {
-resume_23:
-resume_24:
-        if (!write_meta_block(23))
-        {
-            return false;
-        }
-        // Recheck the object because it could be invalidated again
-        cur_obj = bs->heap->read_entry(cur_oid, &modified_block);
-        if (!cur_obj)
-        {
-            // Abort compaction
-            goto resume_0;
-        }
-    }
-    bs->heap->mark_object_compacted(cur_obj, compact_lsn);
-    // Done
-    if (bs->log_level > 10)
-        printf("Compacted %jx:%jx l%ju (%d writes)\n", cur_oid.inode, cur_oid.stripe, compact_lsn, copy_count);
-    flusher->compact_counter++;
-    flusher->active_flushers--;
-    // Advance compacted_lsn every <journal_trim_interval> objects
-    if (co_id == 0 && !((++flusher->advance_lsn_counter) % bs->journal_trim_interval))
-    {
-        flusher->advance_lsn_counter = 0;
-resume_11:
+    bs->heap->add_compact(cur_obj, compact_info.compact_lsn, &modified_block, new_csums);
 resume_12:
 resume_13:
-resume_14:
-resume_15:
-        if (!trim_lsn(11))
-            return false;
+    if (!write_meta_block(12))
+    {
+        return false;
     }
+    // Done
+    if (bs->log_level > 10)
+    {
+        printf("Compacted %jx:%jx l%ju (%d writes)\n", cur_oid.inode, cur_oid.stripe, compact_info.compact_lsn, copy_count);
+    }
+    flusher->compact_counter++;
+    flusher->active_flushers--;
     if (should_repeat)
     {
         // Flush the same object again
@@ -409,11 +401,11 @@ void journal_flusher_co::fill_partial_checksum_blocks()
                 .copy_flags = COPY_BUF_DATA | copy_flags,
                 .offset = blk_begin,
                 .len = blk_end - blk_begin,
-                .disk_loc = end_wr->big_location(bs->heap),
+                .disk_loc = compact_info.clean_loc,
                 .disk_offset = blk_begin,
                 .disk_len = blk_end - blk_begin,
                 .buf = (uint8_t*)memalign_or_die(MEM_ALIGNMENT, blk_end - blk_begin),
-                .wr_lsn = end_wr->lsn,
+                .wr_lsn = compact_info.clean_lsn,
             });
         }
         auto & vec = read_vec[read_vec.size()-1];
@@ -451,16 +443,18 @@ int journal_flusher_co::check_and_punch_checksums()
         return 0;
     }
     // Verify data checksums
-    cur_obj = bs->heap->read_locked_entry(cur_oid, copy_id);
+    cur_obj = bs->heap->read_entry(cur_oid);
     bool csum_ok = true;
     for (int i = 0; i < read_vec.size(); i++)
     {
         auto & vec = read_vec[i];
         if (!(vec.copy_flags & (COPY_BUF_COALESCED|COPY_BUF_ZERO|COPY_BUF_SKIP_CSUM)))
         {
-            heap_write_t *wr = cur_obj->get_writes();
+            heap_entry_t *wr = cur_obj;
             while (wr && wr->lsn != vec.wr_lsn)
-                wr = wr->next();
+            {
+                wr = bs->heap->prev(wr);
+            }
             assert(wr);
             uint32_t *csums = (uint32_t*)(wr->get_checksums(bs->heap)
                 + (vec.disk_offset/bs->dsk.csum_block_size)*(bs->dsk.data_csum_type & 0xFF)
@@ -489,20 +483,30 @@ int journal_flusher_co::check_and_punch_checksums()
         // Nothing to do
         return 0;
     }
-    cur_obj = bs->heap->read_entry(cur_oid, &modified_block);
+    cur_obj = bs->heap->read_entry(cur_oid);
     if (!cur_obj)
     {
         // Object is deleted, abort compaction
         return ENOENT;
     }
-    bs->heap->get_compact_range(cur_obj, compact_lsn, &begin_wr, &end_wr);
-    if (!begin_wr)
+    heap_entry_t *clean_wr = NULL;
+    for (auto wr = cur_obj; wr; wr = bs->heap->prev(wr))
     {
-        // Object is overwritten, abort compaction
-        return ENOENT;
+        if (wr->is_overwrite() && wr->lsn > compact_info.clean_lsn &&
+            wr->lsn <= fsynced_lsn)
+        {
+            // Object is overwritten, abort compaction
+            return ENOENT;
+        }
+        if (wr->lsn == compact_info.clean_lsn)
+        {
+            clean_wr = wr;
+            break;
+        }
     }
-    uint8_t *bmp = end_wr->get_int_bitmap(bs->heap);
-    uint8_t *csums = end_wr->get_checksums(bs->heap);
+    assert(clean_wr);
+    memcpy(new_bmp, clean_wr->get_int_bitmap(bs->heap), bs->dsk.clean_entry_bitmap_size);
+    memcpy(new_csums, clean_wr->get_checksums(bs->heap), bs->dsk.data_block_size/bs->dsk.csum_block_size * (bs->dsk.data_csum_type & 0xFF));
     // Clear bits
     for (auto & vec: read_vec)
     {
@@ -513,7 +517,7 @@ int journal_flusher_co::check_and_punch_checksums()
         if (!(vec.copy_flags & COPY_BUF_COALESCED) &&
             ((vec.offset % bs->dsk.csum_block_size) || (vec.len % bs->dsk.csum_block_size)))
         {
-            bitmap_clear(bmp, vec.offset, vec.len, bs->dsk.bitmap_granularity);
+            bitmap_clear(new_bmp, vec.offset, vec.len, bs->dsk.bitmap_granularity);
         }
     }
     // Update partial block checksums
@@ -522,17 +526,10 @@ int journal_flusher_co::check_and_punch_checksums()
         if (vec.copy_flags & COPY_BUF_CSUM_FILL)
         {
             uint32_t csum_off = vec.offset/bs->dsk.csum_block_size * (bs->dsk.data_csum_type & 0xFF);
-            bs->heap->calc_block_checksums((uint32_t*)(csums+csum_off), vec.buf, bmp, vec.offset, vec.offset+vec.len, true, NULL);
+            bs->heap->calc_block_checksums((uint32_t*)(new_csums+csum_off), vec.buf, new_bmp, vec.offset, vec.offset+vec.len, true, NULL);
         }
     }
-    cur_obj->crc32c = cur_obj->calc_crc32c();
-    if (res == ENOENT)
-    {
-        // Object is deleted, abort compaction
-        return ENOENT;
-    }
-    // Modified, we should write the block to disk
-    assert(!res);
+    // Modified, we should add_punch_holes and then write the block to disk
     return EBUSY;
 }
 
@@ -542,20 +539,30 @@ bool journal_flusher_co::calc_block_checksums()
     {
         return true;
     }
-    bs->heap->get_compact_range(cur_obj, compact_lsn, &begin_wr, &end_wr);
-    if (!begin_wr)
+    heap_entry_t *clean_wr = NULL;
+    for (auto wr = cur_obj; wr; wr = bs->heap->prev(wr))
     {
-        // Object is overwritten, abort compaction
-        return false;
+        if (wr->is_overwrite() && wr->lsn > compact_info.clean_lsn &&
+            wr->lsn <= fsynced_lsn)
+        {
+            // Object is overwritten, abort compaction
+            return false;
+        }
+        if (wr->lsn == compact_info.clean_lsn)
+        {
+            clean_wr = wr;
+            break;
+        }
     }
-    uint8_t *bmp = end_wr->get_int_bitmap(bs->heap);
-    uint8_t *csums = end_wr->get_checksums(bs->heap);
+    assert(clean_wr);
+    memcpy(new_bmp, clean_wr->get_int_bitmap(bs->heap), bs->dsk.clean_entry_bitmap_size);
+    memcpy(new_csums, clean_wr->get_checksums(bs->heap), bs->dsk.data_block_size/bs->dsk.csum_block_size * (bs->dsk.data_csum_type & 0xFF));
     // Set bits
     for (auto & vec: read_vec)
     {
         if (!(vec.copy_flags & (COPY_BUF_COALESCED|COPY_BUF_CSUM_FILL)))
         {
-            bitmap_set(bmp, vec.offset, vec.len, bs->dsk.bitmap_granularity);
+            bitmap_set(new_bmp, vec.offset, vec.len, bs->dsk.bitmap_granularity);
         }
     }
     // Update block checksums
@@ -576,7 +583,7 @@ bool journal_flusher_co::calc_block_checksums()
         assert(!(end % bs->dsk.csum_block_size));
         uint32_t csum_off = start/bs->dsk.csum_block_size * (bs->dsk.data_csum_type & 0xFF);
         bs->heap->calc_block_checksums(
-            (uint32_t*)(csums+csum_off), bmp, start, end,
+            (uint32_t*)(new_csums+csum_off), new_bmp, start, end,
             [&](uint32_t start, uint32_t & len)
             {
                 // O(n^2) search, may be fixed later :-p
@@ -593,7 +600,6 @@ bool journal_flusher_co::calc_block_checksums()
             }, true, NULL
         );
     }
-    cur_obj->crc32c = cur_obj->calc_crc32c();
     return true;
 }
 
@@ -603,13 +609,15 @@ bool journal_flusher_co::write_meta_block(int wait_base)
         goto resume_0;
     else if (wait_state == wait_base+1)
         goto resume_1;
-    await_sqe(0);
-    data->iov = (struct iovec){ bs->heap->get_meta_block(modified_block), (size_t)bs->dsk.meta_block_size };
-    data->callback = simple_callback_w;
-    io_uring_prep_writev(sqe, bs->dsk.meta_fd, &data->iov, 1, bs->dsk.meta_offset + (modified_block+1)*bs->dsk.meta_block_size);
-    wait_count++;
+resume_0:
+    if (bs->ringloop->space_left() < 1)
+    {
+        wait_state = wait_base+0;
+        return 0;
+    }
+    bs->prepare_meta_block_write(modified_block);
 resume_1:
-    if (wait_count > 0)
+    if (bs->meta_block_is_pending(modified_block))
     {
         wait_state = wait_base+1;
         return false;
@@ -664,11 +672,11 @@ bool journal_flusher_co::fsync_meta(int wait_base)
     if (wait_state == wait_base)        goto resume_0;
     else if (wait_state == wait_base+1) goto resume_1;
     else if (wait_state == wait_base+2) goto resume_2;
-resume_0:
     if (bs->dsk.disable_meta_fsync)
     {
         return true;
     }
+resume_0:
     if (flusher->wanting_meta_fsync || flusher->fsyncing_meta > 0)
     {
         wait_state = wait_base;
@@ -693,69 +701,31 @@ resume_2:
     return true;
 }
 
-int journal_flusher_co::fsync_buffer(int wait_base)
-{
-    if (wait_state == wait_base)        goto resume_0;
-    else if (wait_state == wait_base+1) goto resume_1;
-    if (bs->dsk.disable_journal_fsync && bs->dsk.disable_meta_fsync && bs->dsk.disable_data_fsync || !bs->unsynced_big_write_count && !bs->unsynced_small_write_count)
-    {
-        return 1;
-    }
-    if (flusher->syncing_buffer)
-    {
-        return 0;
-    }
-    flusher->active_flushers++;
-    flusher->syncing_buffer++;
-resume_0:
-    assert(!wait_count);
-    compact_lsn = bs->heap->get_completed_lsn();
-    if (!bs->submit_fsyncs(wait_count))
-    {
-        wait_state = wait_base+0;
-        return 0;
-    }
-resume_1:
-    if (wait_count > 0)
-    {
-        wait_state = wait_base+1;
-        return 0;
-    }
-    bs->heap->mark_lsn_fsynced(compact_lsn);
-    flusher->active_flushers--;
-    flusher->syncing_buffer--;
-    return 2;
-}
-
-bool journal_flusher_co::trim_lsn(int wait_base)
+bool journal_flusher_co::fsync_buffer(int wait_base)
 {
     if (wait_state == wait_base)        goto resume_0;
     else if (wait_state == wait_base+1) goto resume_1;
     else if (wait_state == wait_base+2) goto resume_2;
-    else if (wait_state == wait_base+3) goto resume_3;
-    else if (wait_state == wait_base+4) goto resume_4;
-    compact_lsn = bs->heap->get_compacted_lsn();
-    if (((blockstore_meta_header_v3_t*)bs->meta_superblock)->compacted_lsn == compact_lsn)
+    if (bs->dsk.disable_journal_fsync && bs->dsk.disable_meta_fsync && bs->dsk.disable_data_fsync ||
+        !bs->unsynced_big_write_count && !bs->unsynced_small_write_count)
     {
         return true;
     }
-    flusher->active_flushers++;
-    assert(!wait_count);
-    if (!bs->dsk.disable_meta_fsync)
+resume_0:
+    if (flusher->syncing_buffer)
     {
-        await_sqe(0);
-        data->iov = { 0 };
-        data->callback = simple_callback_w;
-        io_uring_prep_fsync(sqe, bs->dsk.meta_fd, IORING_FSYNC_DATASYNC);
-        wait_count++;
+        wait_state = wait_base+0;
+        return false;
     }
-    if (!bs->dsk.disable_data_fsync && bs->dsk.data_fd != bs->dsk.meta_fd)
+    flusher->active_flushers++;
+    flusher->syncing_buffer++;
+resume_1:
+    assert(!wait_count);
+    fsynced_lsn = bs->heap->get_completed_lsn();
+    if (!bs->submit_fsyncs(wait_count))
     {
-        await_sqe(1);
-        data->iov = { 0 };
-        data->callback = simple_callback_w;
-        io_uring_prep_fsync(sqe, bs->dsk.data_fd, IORING_FSYNC_DATASYNC);
-        wait_count++;
+        wait_state = wait_base+1;
+        return false;
     }
 resume_2:
     if (wait_count > 0)
@@ -763,23 +733,8 @@ resume_2:
         wait_state = wait_base+2;
         return false;
     }
-    ((blockstore_meta_header_v3_t*)bs->meta_superblock)->compacted_lsn = compact_lsn;
-    ((blockstore_meta_header_v3_t*)bs->meta_superblock)->set_crc32c();
-    await_sqe(3);
-    data->iov = (struct iovec){ bs->meta_superblock, (size_t)bs->dsk.meta_block_size };
-    data->callback = simple_callback_w;
-    io_uring_prep_writev(sqe, bs->dsk.meta_fd, &data->iov, 1, bs->dsk.meta_offset);
-    // Update superblock with datasync
-    sqe->rw_flags = RWF_DSYNC;
-    wait_count++;
-resume_4:
-    if (wait_count > 0)
-    {
-        wait_state = wait_base+4;
-        return false;
-    }
-    bs->heap->mark_lsn_trimmed(compact_lsn);
-    flusher->compact_counter++;
+    bs->heap->mark_lsn_fsynced(fsynced_lsn);
     flusher->active_flushers--;
+    flusher->syncing_buffer--;
     return true;
 }
diff --git a/src/blockstore/blockstore_flush.h b/src/blockstore/blockstore_flush.h
index 3ed9d2ff..82e3ed66 100644
--- a/src/blockstore/blockstore_flush.h
+++ b/src/blockstore/blockstore_flush.h
@@ -36,26 +36,23 @@ class journal_flusher_co
     int wait_state, wait_count;
     struct io_uring_sqe *sqe;
     struct ring_data_t *data;
+    uint8_t *new_csums = NULL;
+    uint8_t *new_bmp = NULL;
 
     std::function<void(ring_data_t*)> simple_callback_r, simple_callback_w;
 
     object_id cur_oid;
-    uint64_t copy_id;
-    uint64_t compact_lsn;
-    uint64_t cur_version;
-    heap_object_t *cur_obj;
-    heap_write_t *begin_wr, *end_wr;
+    heap_entry_t *cur_obj;
+    uint64_t fsynced_lsn;
+    heap_compact_t compact_info;
     uint32_t modified_block;
     bool should_repeat;
 
     std::vector<copy_buffer_t> read_vec;
     uint32_t overwrite_start, overwrite_end;
-    uint32_t big_start, big_end;
     int i, res;
     bool read_to_fill_incomplete;
     int copy_count;
-    uint64_t clean_loc;
-    flusher_meta_write_t meta_old, meta_new;
     bool do_repeat = false;
 
     friend class journal_flusher_t;
@@ -68,8 +65,7 @@ class journal_flusher_co
     bool write_meta_block(int wait_base);
     bool read_buffered(int wait_base);
     bool fsync_meta(int wait_base);
-    int fsync_buffer(int wait_base);
-    bool trim_lsn(int wait_base);
+    bool fsync_buffer(int wait_base);
 public:
     journal_flusher_co();
     ~journal_flusher_co();
diff --git a/src/blockstore/blockstore_impl.cpp b/src/blockstore/blockstore_impl.cpp
index 58bdb2fc..c05d1fc2 100644
--- a/src/blockstore/blockstore_impl.cpp
+++ b/src/blockstore/blockstore_impl.cpp
@@ -197,6 +197,12 @@ void blockstore_impl_t::loop()
         {
             throw std::runtime_error(std::string("io_uring_submit: ") + strerror(-ret));
         }
+        for (auto & block_num: pending_modified_blocks)
+        {
+            heap->start_block_write(block_num);
+            modified_blocks.insert(block_num);
+        }
+        pending_modified_blocks.clear();
         if ((initial_ring_space - ringloop->space_left()) > 0)
         {
             live = true;
diff --git a/src/blockstore/blockstore_impl.h b/src/blockstore/blockstore_impl.h
index 67a19d0f..fa2c1113 100644
--- a/src/blockstore/blockstore_impl.h
+++ b/src/blockstore/blockstore_impl.h
@@ -53,8 +53,8 @@ struct blockstore_op_private_t
     int pending_ops;
     int op_state;
 
-    // Read, write, sync, stabilize
-    uint64_t lsn;
+    // Write, sync, stabilize
+    uint32_t modified_block, modified_block2;
 
     // Read
     std::vector<copy_buffer_t> read_vec;
@@ -66,9 +66,6 @@ struct blockstore_op_private_t
     // Stabilize, rollback
     int stab_pos;
 
-    // Stabilize
-    uint64_t to_lsn;
-
     // Write
     struct iovec iov_zerofill[3];
     timespec tv_begin;
@@ -119,6 +116,9 @@ public:
     int unsynced_queued_ops = 0;
     uint8_t *zero_object = NULL;
 
+    std::vector<uint32_t> pending_modified_blocks;
+    robin_hood::unordered_flat_set<uint32_t> modified_blocks;
+
     journal_flusher_t *flusher;
     int write_iodepth = 0;
     int inflight_big = 0;
@@ -153,11 +153,11 @@ public:
     // Read
     int dequeue_read(blockstore_op_t *op);
     int fulfill_read(blockstore_op_t *op);
-    uint32_t prepare_read(std::vector<copy_buffer_t> & read_vec, heap_object_t *obj, heap_write_t *wr, uint32_t start, uint32_t end);
-    uint32_t prepare_read_with_bitmaps(std::vector<copy_buffer_t> & read_vec, heap_object_t *obj, heap_write_t *wr, uint32_t start, uint32_t end);
+    uint32_t prepare_read(std::vector<copy_buffer_t> & read_vec, heap_entry_t *obj, heap_entry_t *wr, uint32_t start, uint32_t end);
+    uint32_t prepare_read_with_bitmaps(std::vector<copy_buffer_t> & read_vec, heap_entry_t *obj, heap_entry_t *wr, uint32_t start, uint32_t end);
     uint32_t prepare_read_zero(std::vector<copy_buffer_t> & read_vec, uint32_t start, uint32_t end);
-    uint32_t prepare_read_simple(std::vector<copy_buffer_t> & read_vec, heap_object_t *obj, heap_write_t *wr, uint32_t start, uint32_t end);
-    void prepare_disk_read(std::vector<copy_buffer_t> & read_vec, int pos, heap_object_t *obj, heap_write_t *wr,
+    uint32_t prepare_read_simple(std::vector<copy_buffer_t> & read_vec, heap_entry_t *obj, heap_entry_t *wr, uint32_t start, uint32_t end);
+    void prepare_disk_read(std::vector<copy_buffer_t> & read_vec, int pos, heap_entry_t *obj, heap_entry_t *wr,
         uint32_t blk_start, uint32_t blk_end, uint32_t start, uint32_t end, uint32_t copy_flags);
     void find_holes(std::vector<copy_buffer_t> & read_vec, uint32_t item_start, uint32_t item_end,
         std::function<void(int&, uint32_t, uint32_t)> callback);
@@ -167,9 +167,10 @@ public:
 
     // Write
     bool enqueue_write(blockstore_op_t *op);
-    void prepare_meta_block_write(blockstore_op_t *op, uint64_t modified_block, io_uring_sqe *sqe = NULL);
+    void prepare_meta_block_write(uint32_t modified_block);
+    bool meta_block_is_pending(uint32_t modified_block);
+    bool intent_write_allowed(blockstore_op_t *op, heap_entry_t *obj);
     int dequeue_write(blockstore_op_t *op);
-    int make_big_write(blockstore_op_t *op, uint32_t offset, uint32_t len, uint32_t *modified_block, uint32_t *moved_from_block);
     int continue_write(blockstore_op_t *op);
     void handle_write_event(ring_data_t *data, blockstore_op_t *op);
 
diff --git a/src/blockstore/blockstore_init.cpp b/src/blockstore/blockstore_init.cpp
index 4a8b3e80..8a39829d 100644
--- a/src/blockstore/blockstore_init.cpp
+++ b/src/blockstore/blockstore_init.cpp
@@ -79,7 +79,6 @@ resume_1:
             hdr->meta_block_size = bs->dsk.meta_block_size;
             hdr->data_block_size = bs->dsk.data_block_size;
             hdr->bitmap_granularity = bs->dsk.bitmap_granularity;
-            hdr->compacted_lsn = 0;
             if (bs->dsk.meta_format >= BLOCKSTORE_META_FORMAT_V2)
             {
                 hdr->data_csum_type = bs->dsk.data_csum_type;
@@ -156,7 +155,6 @@ resume_1:
         bs->dsk.check_lengths();
     }
     bs->init();
-    bs->heap->set_compacted_lsn(((blockstore_meta_header_v3_t *)bs->meta_superblock)->compacted_lsn);
     if (bs->dsk.inmemory_journal)
     {
         // Read buffer area
@@ -224,7 +222,11 @@ resume_4:
         if (bufs[i].state == INIT_META_READ_DONE)
         {
             // Handle result
-            entries_loaded += bs->heap->load_blocks(bufs[i].offset-bs->dsk.meta_block_size, bufs[i].size, bufs[i].buf);
+            uint64_t loaded = 0;
+            int r = bs->heap->load_blocks(bufs[i].offset-bs->dsk.meta_block_size, bufs[i].size, bufs[i].buf, loaded);
+            if (r != 0)
+                exit(1);
+            entries_loaded += loaded;
             bufs[i].state = 0;
             bs->ringloop->wakeup();
         }
diff --git a/src/blockstore/blockstore_read.cpp b/src/blockstore/blockstore_read.cpp
index c72efb12..9204c063 100644
--- a/src/blockstore/blockstore_read.cpp
+++ b/src/blockstore/blockstore_read.cpp
@@ -7,7 +7,7 @@
 
 int blockstore_impl_t::dequeue_read(blockstore_op_t *op)
 {
-    heap_object_t *obj = heap->lock_and_read_entry(op->oid, PRIV(op)->lsn);
+    heap_entry_t *obj = heap->lock_and_read_entry(op->oid);
     if (!obj)
     {
         op->version = 0;
@@ -20,11 +20,11 @@ int blockstore_impl_t::dequeue_read(blockstore_op_t *op)
     auto & rv = PRIV(op)->read_vec;
     uint64_t result_version = 0;
     bool found = false;
-    for (auto wr = obj->get_writes(); wr; wr = wr->next())
+    heap->iterate_with_stable(obj, obj->lsn, [&](heap_entry_t *wr, bool stable)
     {
         if (op->version < wr->version)
         {
-            continue;
+            return true;
         }
         if (!found)
         {
@@ -37,16 +37,16 @@ int blockstore_impl_t::dequeue_read(blockstore_op_t *op)
         }
         fulfilled += prepare_read(PRIV(op)->read_vec, obj, wr, op->offset, op->offset+op->len);
         if (fulfilled == op->len ||
-            wr->type() == BS_HEAP_BIG_WRITE ||
-            wr->type() == BS_HEAP_TOMBSTONE)
+            wr->type() == BS_HEAP_BIG_WRITE || wr->type() == BS_HEAP_DELETE)
         {
-            break;
+            return false;
         }
-    }
+        return true;
+    });
     if (!found)
     {
         // May happen if there are entries but all of them are > requested version
-        heap->unlock_entry(op->oid, PRIV(op)->lsn);
+        heap->unlock_entry(op->oid);
         op->version = 0;
         op->retval = -ENOENT;
         FINISH_OP(op);
@@ -56,7 +56,7 @@ int blockstore_impl_t::dequeue_read(blockstore_op_t *op)
     if (!fulfill_read(op))
     {
         // Need to wait. undo added requests, unlock lsn
-        heap->unlock_entry(op->oid, PRIV(op)->lsn);
+        heap->unlock_entry(op->oid);
         free_read_buffers(rv);
         rv.clear();
         return 0;
@@ -65,7 +65,7 @@ int blockstore_impl_t::dequeue_read(blockstore_op_t *op)
     if (!PRIV(op)->pending_ops)
     {
         // everything is fulfilled from memory
-        heap->unlock_entry(op->oid, PRIV(op)->lsn);
+        heap->unlock_entry(op->oid);
         op->retval = op->len;
         free_read_buffers(rv);
         FINISH_OP(op);
@@ -108,20 +108,20 @@ int blockstore_impl_t::fulfill_read(blockstore_op_t *op)
     return 1;
 }
 
-uint32_t blockstore_impl_t::prepare_read(std::vector<copy_buffer_t> & read_vec, heap_object_t *obj, heap_write_t *wr, uint32_t start, uint32_t end)
+uint32_t blockstore_impl_t::prepare_read(std::vector<copy_buffer_t> & read_vec, heap_entry_t *obj, heap_entry_t *wr, uint32_t start, uint32_t end)
 {
     if (wr->type() == BS_HEAP_BIG_WRITE)
     {
         return prepare_read_with_bitmaps(read_vec, obj, wr, start, end);
     }
-    if (wr->type() == BS_HEAP_TOMBSTONE)
+    if (wr->type() == BS_HEAP_DELETE)
     {
         return prepare_read_zero(read_vec, start, end);
     }
     return prepare_read_simple(read_vec, obj, wr, start, end);
 }
 
-uint32_t blockstore_impl_t::prepare_read_with_bitmaps(std::vector<copy_buffer_t> & read_vec, heap_object_t *obj, heap_write_t *wr, uint32_t start, uint32_t end)
+uint32_t blockstore_impl_t::prepare_read_with_bitmaps(std::vector<copy_buffer_t> & read_vec, heap_entry_t *obj, heap_entry_t *wr, uint32_t start, uint32_t end)
 {
     // BIG_WRITEs contain a bitmap and we have to handle its holes
     uint32_t res = 0;
@@ -166,7 +166,7 @@ uint32_t blockstore_impl_t::prepare_read_zero(std::vector<copy_buffer_t> & read_
     return res;
 }
 
-uint32_t blockstore_impl_t::prepare_read_simple(std::vector<copy_buffer_t> & read_vec, heap_object_t *obj, heap_write_t *wr, uint32_t start, uint32_t end)
+uint32_t blockstore_impl_t::prepare_read_simple(std::vector<copy_buffer_t> & read_vec, heap_entry_t *obj, heap_entry_t *wr, uint32_t start, uint32_t end)
 {
     uint32_t res = 0;
     if (wr->type() == BS_HEAP_SMALL_WRITE || wr->type() == BS_HEAP_INTENT_WRITE)
@@ -212,10 +212,14 @@ uint32_t blockstore_impl_t::prepare_read_simple(std::vector<copy_buffer_t> & rea
             uint32_t skip_csum = 0;
             if (!perfect_csum_update && wr->type() == BS_HEAP_BIG_WRITE)
             {
-                for (auto owr = obj->get_writes(); owr && owr != wr; owr = owr->next())
+                for (auto owr = obj; owr && owr != wr; owr = heap->prev(owr))
+                {
                     if ((owr->type() == BS_HEAP_INTENT_WRITE || owr->type() == BS_HEAP_SMALL_WRITE) &&
                         owr->small().offset < blk_end && owr->small().offset+owr->small().len > blk_start)
+                    {
                         skip_csum = COPY_BUF_SKIP_CSUM;
+                    }
+                }
             }
             if ((blk_end-1)/dsk.csum_block_size == blk_start/dsk.csum_block_size ||
                 blk_end/dsk.csum_block_size == blk_start/dsk.csum_block_size+1 && blk_end != end && blk_start != start ||
@@ -243,18 +247,34 @@ uint32_t blockstore_impl_t::prepare_read_simple(std::vector<copy_buffer_t> & rea
     return res;
 }
 
-void blockstore_impl_t::prepare_disk_read(std::vector<copy_buffer_t> & read_vec, int pos, heap_object_t *obj, heap_write_t *wr,
+void blockstore_impl_t::prepare_disk_read(std::vector<copy_buffer_t> & read_vec, int pos, heap_entry_t *obj, heap_entry_t *wr,
     uint32_t blk_start, uint32_t blk_end, uint32_t start, uint32_t end, uint32_t copy_flags)
 {
     // Only one INTENT_WRITE is allowed at a time
-    assert(wr->type() != BS_HEAP_INTENT_WRITE || wr->next()->type() == BS_HEAP_BIG_WRITE);
+    uint64_t loc = 0;
+    if (wr->type() == BS_HEAP_INTENT_WRITE)
+    {
+        heap_entry_t *big_wr = wr;
+        while (big_wr && big_wr->type() == BS_HEAP_INTENT_WRITE)
+        {
+            big_wr = heap->prev(big_wr);
+        }
+        assert(big_wr);
+        loc = big_wr->big_location(heap);
+    }
+    else if (wr->type() == BS_HEAP_SMALL_WRITE)
+    {
+        loc = wr->small().location-wr->small().offset;
+    }
+    else /*if (wr->type() == BS_HEAP_BIG_WRITE)*/
+    {
+        loc = wr->big_location(heap);
+    }
     copy_buffer_t vec = {
         .copy_flags = (wr->type() == BS_HEAP_SMALL_WRITE ? COPY_BUF_JOURNAL : COPY_BUF_DATA) | copy_flags,
         .offset = start,
         .len = end-start,
-        .disk_loc = (wr->type() == BS_HEAP_INTENT_WRITE ? wr->next()->big_location(heap)
-            : (wr->type() == BS_HEAP_SMALL_WRITE ? wr->small().location-wr->small().offset
-            : wr->big_location(heap))),
+        .disk_loc = loc,
         .disk_offset = blk_start,
         .disk_len = blk_end - blk_start,
         .wr_lsn = wr->lsn,
@@ -349,7 +369,7 @@ void blockstore_impl_t::handle_read_event(ring_data_t *data, blockstore_op_t *op
             op->retval = -EDOM;
         else if (op->retval == 0)
             op->retval = op->len;
-        heap->unlock_entry(op->oid, PRIV(op)->lsn);
+        heap->unlock_entry(op->oid);
         free_read_buffers(PRIV(op)->read_vec);
         FINISH_OP(op);
     }
@@ -357,7 +377,7 @@ void blockstore_impl_t::handle_read_event(ring_data_t *data, blockstore_op_t *op
 
 bool blockstore_impl_t::verify_read_checksums(blockstore_op_t *op)
 {
-    heap_object_t *obj = heap->read_locked_entry(op->oid, PRIV(op)->lsn);
+    heap_entry_t *obj = heap->read_entry(op->oid);
     auto & rv = PRIV(op)->read_vec;
     for (auto & vec: rv)
     {
@@ -367,9 +387,9 @@ bool blockstore_impl_t::verify_read_checksums(blockstore_op_t *op)
             memcpy(op->buf + vec.offset - op->offset, vec.buf + vec.offset - vec.disk_offset, vec.len);
         if (vec.copy_flags & (COPY_BUF_COALESCED|COPY_BUF_SKIP_CSUM))
             continue;
-        heap_write_t *wr = obj->get_writes();
+        heap_entry_t *wr = obj;
         while (wr && wr->lsn != vec.wr_lsn)
-            wr = wr->next();
+            wr = heap->prev(wr);
         assert(wr);
         uint8_t *buf = vec.buf ? vec.buf : (op->buf + vec.offset - op->offset);
         uint32_t *csums = (uint32_t*)(wr->get_checksums(heap)
@@ -394,23 +414,29 @@ bool blockstore_impl_t::verify_read_checksums(blockstore_op_t *op)
 
 int blockstore_impl_t::read_bitmap(object_id oid, uint64_t target_version, void *bitmap, uint64_t *result_version)
 {
-    heap_object_t *obj = heap->read_entry(oid, NULL);
+    heap_entry_t *obj = heap->read_entry(oid);
     if (obj)
     {
-        for (auto wr = obj->get_writes(); wr; wr = wr->next())
+        bool found = false;
+        heap->iterate_with_stable(obj, obj->lsn, [&](heap_entry_t *wr, bool stable)
         {
-            if (target_version < wr->version)
+            if (target_version >= wr->version)
             {
-                continue;
-            }
-            if (result_version)
-            {
-                *result_version = wr->version;
-            }
-            if (bitmap)
-            {
-                memcpy(bitmap, wr->get_ext_bitmap(heap), dsk.clean_entry_bitmap_size);
+                found = true;
+                if (result_version)
+                {
+                    *result_version = wr->version;
+                }
+                if (bitmap)
+                {
+                    memcpy(bitmap, wr->get_ext_bitmap(heap), dsk.clean_entry_bitmap_size);
+                }
+                return false;
             }
+            return true;
+        });
+        if (found)
+        {
             return 0;
         }
     }
diff --git a/src/blockstore/blockstore_stable.cpp b/src/blockstore/blockstore_stable.cpp
index 010d7360..f3253ec4 100644
--- a/src/blockstore/blockstore_stable.cpp
+++ b/src/blockstore/blockstore_stable.cpp
@@ -13,73 +13,76 @@ int blockstore_impl_t::dequeue_stable(blockstore_op_t *op)
     else if (priv->op_state == 2) goto resume_2;
     else if (priv->op_state == 3) goto resume_3;
     else if (priv->op_state == 4) goto resume_4;
+    else if (priv->op_state == 5) goto resume_5;
     assert(!priv->op_state);
-    // Modify in-memory state and assign contiguous LSNs
-    priv->stab_pos = 0;
-    priv->lsn = priv->to_lsn = 0;
     op->retval = 0;
-    while (priv->stab_pos < op->len)
+    priv->modified_block = priv->modified_block2 = UINT32_MAX;
+    for (priv->stab_pos = 0; priv->stab_pos < op->len; priv->stab_pos++)
     {
-        uint32_t modified_block = 0;
-        uint64_t new_lsn = 0;
-        uint64_t new_to_lsn = 0;
-        int res = op->opcode == BS_OP_STABLE
-            ? heap->post_stabilize(v[priv->stab_pos].oid, v[priv->stab_pos].version, &modified_block, &new_lsn, &new_to_lsn)
-            : heap->post_rollback(v[priv->stab_pos].oid, v[priv->stab_pos].version, &new_lsn, &modified_block);
-        if (res != 0)
         {
-            assert(res == ENOENT || res == EBUSY);
-            op->retval = -res;
-        }
-        if (new_lsn)
-        {
-            assert(priv->lsn == 0 || priv->to_lsn == new_lsn-1);
-            if (!priv->lsn)
-                priv->lsn = new_lsn;
-            priv->to_lsn = op->opcode == BS_OP_STABLE ? new_to_lsn : new_lsn;
-        }
-        priv->stab_pos++;
-    }
-    // Submit metadata writes
-    priv->stab_pos = 0;
-resume_1:
-    priv->op_state = 1;
-    while (priv->stab_pos < op->len)
-    {
-        uint32_t block_num = 0;
-        heap_object_t *obj = heap->read_entry(v[priv->stab_pos].oid, &block_num);
-        if (obj)
-        {
-            io_uring_sqe *sqe = get_sqe();
-            if (!sqe)
+            auto obj = heap->read_entry(v[priv->stab_pos].oid);
+            if (!obj)
             {
-                if (priv->pending_ops > 0)
-                    return 1;
-                priv->wait_detail = 1;
-                priv->wait_for = WAIT_SQE;
+                op->retval = -ENOENT;
+                FINISH_OP(op);
+                return 2;
+            }
+            int res = op->opcode == BS_OP_STABLE
+                ? heap->add_commit(obj, v[priv->stab_pos].version, &priv->modified_block2)
+                : heap->add_rollback(obj, v[priv->stab_pos].version, &priv->modified_block2);
+            if (res == EBUSY)
+            {
+                op->retval = -EBUSY;
+                FINISH_OP(op);
+                return 2;
+            }
+            if (res == ENOSPC)
+            {
+                if (!heap->get_inflight_queue_size())
+                {
+                    // no space
+                    op->retval = -ENOSPC;
+                    FINISH_OP(op);
+                    return 2;
+                }
+                if (priv->modified_block2 != UINT32_MAX)
+                {
+                    priv->stab_pos--;
+                    goto resume_1;
+                }
+                priv->wait_for = WAIT_COMPACTION;
+                priv->wait_detail = flusher->get_compact_counter();
+                flusher->request_trim();
                 return 0;
             }
-            prepare_meta_block_write(op, block_num, sqe);
+            assert(res == 0);
+        }
+        if (priv->modified_block != UINT32_MAX && priv->modified_block2 != priv->modified_block)
+        {
+resume_1:
+            BS_SUBMIT_CHECK_SQES(1);
+            prepare_meta_block_write(priv->modified_block);
+resume_2:
+            if (meta_block_is_pending(priv->modified_block))
+            {
+                priv->op_state = 2;
+                return 1;
+            }
+        }
+        priv->modified_block = priv->modified_block2;
+        if (priv->stab_pos == op->len-1 && priv->modified_block2 != UINT32_MAX)
+        {
+            priv->modified_block2 = UINT32_MAX;
+            goto resume_1;
         }
-        priv->stab_pos++;
-    }
-    if (priv->pending_ops > 0)
-    {
-        priv->op_state = 1;
-        return 1;
-    }
-    // Mark writes as completed to allow compaction
-    for (uint64_t lsn = priv->lsn; lsn <= priv->to_lsn; lsn++)
-    {
-        heap->mark_lsn_completed(lsn);
     }
     unsynced_meta_write_count++;
     // Fsync, just because our semantics imply that commit (stabilize) is immediately fsynced
-    priv->op_state = 2;
-resume_2:
+    priv->op_state = 3;
 resume_3:
 resume_4:
-    int res = do_sync(op, 2);
+resume_5:
+    int res = do_sync(op, 3);
     if (res != 2)
     {
         return res;
diff --git a/src/blockstore/blockstore_sync.cpp b/src/blockstore/blockstore_sync.cpp
index fc136d5b..99a9894d 100644
--- a/src/blockstore/blockstore_sync.cpp
+++ b/src/blockstore/blockstore_sync.cpp
@@ -96,7 +96,7 @@ int blockstore_impl_t::do_sync(blockstore_op_t *op, int base_state)
         unsynced_big_write_count = unsynced_small_write_count = unsynced_meta_write_count = 0;
         return 2;
     }
-    PRIV(op)->lsn = heap->get_completed_lsn();
+    PRIV(op)->modified_block = heap->get_completed_lsn();
     if (!submit_fsyncs(PRIV(op)->pending_ops))
     {
         PRIV(op)->wait_detail = 1;
@@ -110,6 +110,6 @@ resume_1:
         return 1;
     }
 resume_2:
-    heap->mark_lsn_fsynced(PRIV(op)->lsn);
+    heap->mark_lsn_fsynced(PRIV(op)->modified_block);
     return 2;
 }
diff --git a/src/blockstore/blockstore_write.cpp b/src/blockstore/blockstore_write.cpp
index 87f62408..44b88b61 100644
--- a/src/blockstore/blockstore_write.cpp
+++ b/src/blockstore/blockstore_write.cpp
@@ -11,23 +11,108 @@ bool blockstore_impl_t::enqueue_write(blockstore_op_t *op)
     return true;
 }
 
-void blockstore_impl_t::prepare_meta_block_write(blockstore_op_t *op, uint64_t modified_block, io_uring_sqe *sqe)
+void blockstore_impl_t::prepare_meta_block_write(uint32_t modified_block)
 {
-    if (!sqe)
+    //assert(modified_blocks.find(modified_block) == modified_blocks.end());
+    for (auto & block_num: pending_modified_blocks)
     {
-        sqe = get_sqe();
-        assert(sqe != NULL);
+        if (block_num == modified_block)
+            return;
     }
+    io_uring_sqe *sqe = get_sqe();
+    assert(sqe != NULL); // FIXME
+    pending_modified_blocks.push_back(modified_block);
     ring_data_t *data = ((ring_data_t*)sqe->user_data);
     data->iov = (struct iovec){ heap->get_meta_block(modified_block), (size_t)dsk.meta_block_size };
-    data->callback = [this, op](ring_data_t *data) { handle_write_event(data, op); };
-    PRIV(op)->pending_ops++;
+    data->callback = [this, modified_block](ring_data_t *data)
+    {
+        live = true;
+        if (data->res != data->iov.iov_len)
+        {
+            // FIXME: our state becomes corrupted after a write error. maybe do something better than just die
+            disk_error_abort("data write", data->res, data->iov.iov_len);
+        }
+        modified_blocks.erase(modified_block);
+        heap->complete_block_write(modified_block);
+        ringloop->wakeup();
+    };
     io_uring_prep_writev(
         sqe, dsk.meta_fd, &data->iov, 1, dsk.meta_offset + (modified_block+1)*dsk.meta_block_size
     );
 }
 
-// First step of the write algorithm: dequeue operation and submit initial write(s)
+bool blockstore_impl_t::meta_block_is_pending(uint32_t modified_block)
+{
+    auto mb_it = modified_blocks.find(modified_block);
+    if (mb_it != modified_blocks.end())
+        return true;
+    for (auto & block_num: pending_modified_blocks)
+    {
+        if (block_num == modified_block)
+            return true;
+    }
+    return false;
+}
+
+bool blockstore_impl_t::intent_write_allowed(blockstore_op_t *op, heap_entry_t *obj)
+{
+    // Parallel writes to the same object are forbidden so "one intent at a time" is fulfilled automatically
+    // Intent writes are disabled when metadata fsync is enabled
+    if (!dsk.disable_meta_fsync)
+    {
+        return false;
+    }
+    // Intent writes are only for replication
+    if (op->opcode != BS_OP_WRITE_STABLE)
+    {
+        return false;
+    }
+    // Operation size should be less than or equal to atomic write size
+    if (!op->len || op->len > dsk.atomic_write_size)
+    {
+        return false;
+    }
+    // Intent-writes are disabled if "absolutely correct during compaction" checksum validation algorithm is enabled
+    // We could also do RMW here when perfect_csum_update is enabled, but it's unclear if we need it
+    if (perfect_csum_update && dsk.csum_block_size > dsk.bitmap_granularity &&
+        ((op->offset % dsk.csum_block_size) || (op->len % dsk.csum_block_size)))
+    {
+        return false;
+    }
+    bool ok = true, has_intent = false;
+    heap->iterate_with_stable(obj, obj->lsn, [&](heap_entry_t *wr, bool stable)
+    {
+        // Intent writes are not allowed over buffered writes
+        if (wr->type() == BS_HEAP_SMALL_WRITE)
+        {
+            ok = false;
+            return false;
+        }
+        // Intent writes are not allowed over unstable writes
+        if (!stable)
+        {
+            ok = false;
+            return false;
+        }
+        // One intent-write is allowed even with fsyncs because BIG_WRITE is always counted as fsynced
+        if (dsk.disable_data_fsync && wr->type() == BS_HEAP_INTENT_WRITE)
+        {
+            if (has_intent)
+            {
+                ok = false;
+                return false;
+            }
+            has_intent = true;
+        }
+        if (wr->type() == BS_HEAP_BIG_WRITE)
+        {
+            return false;
+        }
+        return true;
+    });
+    return ok;
+}
+
 int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
 {
     if (PRIV(op)->op_state)
@@ -38,13 +123,13 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
     {
         return 0;
     }
+    PRIV(op)->modified_block = UINT32_MAX;
     PRIV(op)->is_big = false;
-    uint32_t modified_block = UINT32_MAX, moved_from_block = UINT32_MAX;
-    heap_object_t *obj = heap->read_entry(op->oid, &modified_block);
+    heap_entry_t *obj = heap->read_entry(op->oid);
     if (op->opcode == BS_OP_DELETE)
     {
         // Delete
-        if (!obj)
+        if (!obj || obj->type() == BS_HEAP_DELETE)
         {
             // Already deleted
             op->retval = 0;
@@ -52,24 +137,23 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
             return 2;
         }
         BS_SUBMIT_CHECK_SQES(1);
-        int res = heap->post_delete(modified_block, obj, &PRIV(op)->lsn);
+        int res = heap->add_delete(obj, &PRIV(op)->modified_block);
         assert(res == 0);
-        prepare_meta_block_write(op, modified_block);
+        prepare_meta_block_write(PRIV(op)->modified_block);
+        PRIV(op)->pending_ops++;
         PRIV(op)->op_state = 5;
         write_iodepth++;
     }
+    // FIXME: Add 'big_intent' write mode
     // FIXME: Allow to do initial writes as buffered, not redirected
     // FIXME: Allow to do direct writes over holes
-    else if (!obj || obj->get_writes()->type() == BS_HEAP_TOMBSTONE ||
-        op->offset == 0 && op->len == dsk.data_block_size)
+    else if (!obj || obj->type() == BS_HEAP_DELETE || op->offset == 0 && op->len == dsk.data_block_size)
     {
         // Big (redirect) write
         BS_SUBMIT_CHECK_SQES(1);
         PRIV(op)->is_big = true;
-        uint32_t tmp_block;
         uint64_t loc = heap->find_free_data();
-        if (loc == UINT64_MAX ||
-            !obj && heap->get_block_for_new_object(tmp_block) != 0)
+        if (loc == UINT64_MAX)
         {
             if (!heap->get_inflight_queue_size())
             {
@@ -91,17 +175,6 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
         );
 #endif
         heap->use_data(op->oid.inode, PRIV(op)->location);
-        if (!dsk.disable_data_fsync && dsk.disable_meta_fsync)
-        {
-            // Do big_write as an INTENT to avoid data fsync
-            int res = make_big_write(op, 0, 0, &modified_block, &moved_from_block);
-            assert(res == 0);
-            if (moved_from_block != UINT32_MAX)
-                prepare_meta_block_write(op, moved_from_block);
-            obj = heap->read_entry(op->oid, &modified_block);
-            heap->mark_lsn_completed(PRIV(op)->lsn);
-            goto process_intent;
-        }
         io_uring_sqe *sqe = get_sqe();
         ring_data_t *data = ((ring_data_t*)sqe->user_data);
         uint64_t stripe_offset = (op->offset % dsk.bitmap_granularity);
@@ -128,46 +201,19 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
         write_iodepth++;
         inflight_big++;
     }
-    // Only one INTENT_WRITE is allowed at a time, but in fact,
-    // parallel writes to the same object are forbidden anyway
-    else if (op->len > 0 && op->len <= dsk.atomic_write_size &&
-        // Intent-writes are disabled if "absolutely correct during compaction" checksum validation algorithm is enabled
-        // We could also do RMW here when perfect_csum_update is enabled, but it's unclear if we need it
-        (!perfect_csum_update || dsk.csum_block_size <= dsk.bitmap_granularity ||
-            !(op->offset % dsk.csum_block_size) &&
-            !(op->len % dsk.csum_block_size) &&
-            (obj->get_writes()->entry_type != (BS_HEAP_INTENT_WRITE|BS_HEAP_STABLE) ||
-            obj->get_writes()->can_be_collapsed(heap))) &&
-        // One intent-write is allowed even with fsyncs because BIG_WRITE is always counted as fsynced
-        dsk.disable_meta_fsync &&
-        (op->opcode == BS_OP_WRITE_STABLE &&
-            (obj->get_writes()->entry_type == (BS_HEAP_BIG_WRITE|BS_HEAP_STABLE) ||
-            obj->get_writes()->entry_type == (BS_HEAP_INTENT_WRITE|BS_HEAP_STABLE) && dsk.disable_data_fsync) ||
-        op->opcode == BS_OP_WRITE && obj->get_writes()->entry_type == BS_HEAP_BIG_WRITE))
+    else if (intent_write_allowed(op, obj))
     {
         // Direct intent-write
         BS_SUBMIT_CHECK_SQES(1);
-        if (obj->get_writes()->type() == BS_HEAP_BIG_WRITE)
+        auto wr = obj;
+        while (wr && (wr->type() == BS_HEAP_INTENT_WRITE || wr->type() == BS_HEAP_COMMIT || wr->type() == BS_HEAP_ROLLBACK))
         {
-            PRIV(op)->location = obj->get_writes()->big_location(heap);
+            wr = heap->prev(wr);
         }
-        else
-        {
-            assert(obj->get_writes()->next()->type() == BS_HEAP_BIG_WRITE);
-            PRIV(op)->location = obj->get_writes()->next()->big_location(heap);
-        }
-process_intent:
-        uint8_t wr_buf[heap->get_max_write_entry_size()];
-        heap_write_t *wr = (heap_write_t*)wr_buf;
-        wr->version = op->version;
-        wr->entry_type = BS_HEAP_INTENT_WRITE | (op->opcode == BS_OP_WRITE_STABLE ? BS_HEAP_STABLE : 0);
-        wr->small().offset = op->offset;
-        wr->small().len = op->len;
-        wr->small().location = 0;
-        if (op->bitmap)
-            memcpy(wr->get_ext_bitmap(heap), op->bitmap, dsk.clean_entry_bitmap_size);
-        heap->calc_checksums(wr, (uint8_t*)op->buf, true);
-        int res = heap->post_write(modified_block, op->oid, obj, wr, &moved_from_block);
+        assert(wr->type() == BS_HEAP_BIG_WRITE);
+        PRIV(op)->location = wr->big_location(heap);
+        int res = heap->add_small_write(op->oid, obj, (BS_HEAP_INTENT_WRITE | (op->opcode == BS_OP_WRITE_STABLE ? BS_HEAP_STABLE : 0)),
+            op->version, op->offset, op->len, 0, op->bitmap, (uint8_t*)op->buf, &PRIV(op)->modified_block);
         if (res == EAGAIN)
         {
             assert(heap->get_inflight_queue_size());
@@ -184,10 +230,8 @@ process_intent:
             return 2;
         }
         assert(res == 0);
-        PRIV(op)->lsn = wr->lsn;
-        if (moved_from_block != UINT32_MAX)
-            prepare_meta_block_write(op, moved_from_block);
-        prepare_meta_block_write(op, modified_block);
+        prepare_meta_block_write(PRIV(op)->modified_block);
+        PRIV(op)->pending_ops++;
         PRIV(op)->op_state = 9;
         write_iodepth++;
     }
@@ -205,18 +249,8 @@ process_intent:
         }
         // There is sufficient space. Check SQE(s)
         BS_SUBMIT_CHECK_SQES(1 + (op->len > 0 ? 1 : 0));
-        uint8_t wr_buf[heap->get_max_write_entry_size()];
-        heap_write_t *wr = (heap_write_t*)wr_buf;
-        wr->version = op->version;
-        wr->entry_type = BS_HEAP_SMALL_WRITE | (op->opcode == BS_OP_WRITE_STABLE ? BS_HEAP_STABLE : 0);
-        wr->small().offset = op->offset;
-        wr->small().len = op->len;
-        wr->small().location = loc;
-        PRIV(op)->location = loc;
-        if (op->bitmap)
-            memcpy(wr->get_ext_bitmap(heap), op->bitmap, dsk.clean_entry_bitmap_size);
-        heap->calc_checksums(wr, (uint8_t*)op->buf, true);
-        int res = heap->post_write(modified_block, op->oid, obj, wr, &moved_from_block);
+        int res = heap->add_small_write(op->oid, obj, (BS_HEAP_SMALL_WRITE | (op->opcode == BS_OP_WRITE_STABLE ? BS_HEAP_STABLE : 0)),
+            op->version, op->offset, op->len, loc, op->bitmap, (uint8_t*)op->buf, &PRIV(op)->modified_block);
         if (res == EAGAIN)
         {
             assert(heap->get_inflight_queue_size());
@@ -233,12 +267,10 @@ process_intent:
             return 2;
         }
         assert(res == 0);
-        PRIV(op)->lsn = wr->lsn;
         if (op->len)
             heap->use_buffer_area(op->oid.inode, loc, op->len);
-        if (moved_from_block != UINT32_MAX)
-            prepare_meta_block_write(op, moved_from_block);
-        prepare_meta_block_write(op, modified_block);
+        prepare_meta_block_write(PRIV(op)->modified_block);
+        PRIV(op)->pending_ops++;
         if (op->len > 0)
         {
             // Prepare buffered data write
@@ -263,26 +295,6 @@ process_intent:
     return 1;
 }
 
-int blockstore_impl_t::make_big_write(blockstore_op_t *op, uint32_t offset, uint32_t len, uint32_t *modified_block, uint32_t *moved_from_block)
-{
-    uint8_t wr_buf[heap->get_max_write_entry_size()];
-    heap_write_t *wr = (heap_write_t*)wr_buf;
-    wr->entry_type = BS_HEAP_BIG_WRITE | (op->opcode == BS_OP_WRITE_STABLE ? BS_HEAP_STABLE : 0);
-    wr->version = op->version;
-    wr->set_big_location(heap, PRIV(op)->location);
-    if (op->bitmap)
-        memcpy(wr->get_ext_bitmap(heap), op->bitmap, dsk.clean_entry_bitmap_size);
-    memset(wr->get_int_bitmap(heap), 0, dsk.clean_entry_bitmap_size);
-    bitmap_set(wr->get_int_bitmap(heap), offset, len, dsk.bitmap_granularity);
-    heap->calc_checksums(wr, (uint8_t*)op->buf, true, offset, len);
-    int res = heap->post_write(op->oid, wr, modified_block, moved_from_block);
-    if (res != 0)
-        return res;
-    assert(res == 0);
-    PRIV(op)->lsn = wr->lsn;
-    return 0;
-}
-
 int blockstore_impl_t::continue_write(blockstore_op_t *op)
 {
     int op_state = PRIV(op)->op_state;
@@ -305,6 +317,12 @@ again:
     {
         // In progress
         assert(op_state < 10);
+        if (PRIV(op)->modified_block != UINT32_MAX &&
+            !meta_block_is_pending(PRIV(op)->modified_block))
+        {
+            PRIV(op)->pending_ops--;
+            PRIV(op)->modified_block = UINT32_MAX;
+        }
         if (PRIV(op)->pending_ops > 0)
             return 1;
         op_state++;
@@ -313,7 +331,6 @@ again:
 resume_2:
     // We must fsync all big writes to avoid complex write workflows
     // It's OK for all HDDs and for server SSDs, but slightly worse for desktop SSDs
-    // The other way is to add another type of MVCC to blockstore_heap: "forward" MVCC :)
     inflight_big--;
     if (!dsk.disable_data_fsync)
     {
@@ -349,8 +366,9 @@ resume_12:
     }
 resume_4:
     {
-        uint32_t modified_block = UINT32_MAX, moved_from_block = UINT32_MAX;
-        int res = make_big_write(op, op->offset, op->len, &modified_block, &moved_from_block);
+        auto obj = heap->read_entry(op->oid);
+        int res = heap->add_big_write(op->oid, obj, (op->opcode == BS_OP_WRITE_STABLE), op->version,
+            op->offset, op->len, PRIV(op)->location, op->bitmap, (uint8_t*)op->buf, &PRIV(op)->modified_block);
         if (res == EAGAIN)
         {
             assert(heap->get_inflight_queue_size());
@@ -367,9 +385,9 @@ resume_4:
             FINISH_OP(op);
             return 2;
         }
-        if (moved_from_block != UINT32_MAX)
-            prepare_meta_block_write(op, moved_from_block);
-        prepare_meta_block_write(op, modified_block);
+        assert(res == 0);
+        prepare_meta_block_write(PRIV(op)->modified_block);
+        PRIV(op)->pending_ops++;
         PRIV(op)->op_state = 5;
         return 1;
     }
@@ -411,7 +429,6 @@ resume_8:
     printf("Ack write %jx:%jx v%ju\n", op->oid.inode, op->oid.stripe, op->version);
 #endif
     op->retval = op->len;
-    heap->mark_lsn_completed(PRIV(op)->lsn);
     if (PRIV(op)->is_big)
         unsynced_big_write_count++;
     else
diff --git a/src/disk_tool/disk_simple_offsets.cpp b/src/disk_tool/disk_simple_offsets.cpp
index f174c9dd..a51493f1 100644
--- a/src/disk_tool/disk_simple_offsets.cpp
+++ b/src/disk_tool/disk_simple_offsets.cpp
@@ -132,16 +132,13 @@ void disk_tool_simple_offsets(json11::Json cfg, bool json_output)
     uint64_t meta_size;
     if (meta_format == BLOCKSTORE_META_FORMAT_HEAP)
     {
-        uint32_t min_object_size = sizeof(heap_object_t)+sizeof(heap_write_t)+data_csum_size+2*clean_entry_bitmap_size;
-        uint32_t meta_block_target_free_space = cfg["meta_block_target_free_space"].uint64_value();
-        if (!meta_block_target_free_space || meta_block_target_free_space > device_block_size-min_object_size)
-            meta_block_target_free_space = 800;
+        uint32_t min_object_size = sizeof(heap_big_write_t) + data_csum_size + 2*clean_entry_bitmap_size;
         double meta_reserve = cfg["meta_reserve"].number_value();
         if (!meta_reserve)
             meta_reserve = 1.5;
         else if (meta_reserve < 1)
             meta_reserve = 1;
-        uint32_t entries_per_block = (device_block_size-meta_block_target_free_space) / min_object_size;
+        uint32_t entries_per_block = device_block_size / min_object_size;
         meta_size = device_block_size * (uint64_t)((object_count+entries_per_block-1) / entries_per_block * meta_reserve);
     }
     else if (meta_format == BLOCKSTORE_META_FORMAT_V2)
diff --git a/src/disk_tool/disk_tool.h b/src/disk_tool/disk_tool.h
index c62b55ed..21922293 100644
--- a/src/disk_tool/disk_tool.h
+++ b/src/disk_tool/disk_tool.h
@@ -100,15 +100,15 @@ struct disk_tool_t
     int process_journal(std::function<int(void*)> block_fn, bool do_open = true);
     int process_journal_block(void *buf, std::function<void(int, journal_entry*)> iter_fn);
     int process_meta(std::function<void(blockstore_meta_header_v3_t *)> hdr_fn,
-        std::function<void(blockstore_heap_t *heap, heap_object_t *obj, uint32_t meta_block_num)> obj_fn,
+        std::function<void(blockstore_heap_t *heap, heap_entry_t *obj, uint32_t meta_block_num)> obj_fn,
         std::function<void(uint64_t block_num, clean_disk_entry *entry_v1, uint8_t *bitmap)> record_fn,
         bool with_data, bool do_open);
 
     int dump_meta();
     void dump_meta_header(blockstore_meta_header_v3_t *hdr);
     void dump_meta_entry(uint64_t block_num, clean_disk_entry *entry, uint8_t *bitmap);
-    void dump_heap_entry_as_old(blockstore_heap_t *heap, heap_object_t *obj);
-    void dump_heap_entry(blockstore_heap_t *heap, heap_object_t *obj);
+    void dump_heap_entry_as_old(blockstore_heap_t *heap, heap_entry_t *obj);
+    void dump_heap_entry(blockstore_heap_t *heap, heap_entry_t *obj);
 
     int dump_load_check_superblock(const std::string & device);
 
diff --git a/src/disk_tool/disk_tool_discard.cpp b/src/disk_tool/disk_tool_discard.cpp
index 86d63857..66798542 100644
--- a/src/disk_tool/disk_tool_discard.cpp
+++ b/src/disk_tool/disk_tool_discard.cpp
@@ -55,9 +55,9 @@ int disk_tool_t::trim_data(std::string device)
     data_alloc = new allocator_t(dsk.block_count);
     r = process_meta(
         [this](blockstore_meta_header_v3_t *hdr) {},
-        [this](blockstore_heap_t *heap, heap_object_t *obj, uint32_t meta_block_num)
+        [this](blockstore_heap_t *heap, heap_entry_t *obj, uint32_t meta_block_num)
         {
-            for (auto wr = obj->get_writes(); wr; wr = wr->next())
+            for (auto wr = obj; wr; wr = heap->prev(wr))
             {
                 if ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_BIG_WRITE)
                 {
diff --git a/src/disk_tool/disk_tool_meta.cpp b/src/disk_tool/disk_tool_meta.cpp
index 80e04574..7bee467c 100644
--- a/src/disk_tool/disk_tool_meta.cpp
+++ b/src/disk_tool/disk_tool_meta.cpp
@@ -10,7 +10,7 @@
 #define FREE_SPACE_BIT 0x8000
 
 int disk_tool_t::process_meta(std::function<void(blockstore_meta_header_v3_t *)> hdr_fn,
-    std::function<void(blockstore_heap_t *heap, heap_object_t *obj, uint32_t meta_block_num)> obj_fn,
+    std::function<void(blockstore_heap_t *heap, heap_entry_t *obj, uint32_t meta_block_num)> obj_fn,
     std::function<void(uint64_t block_num, clean_disk_entry *entry_v1, uint8_t *bitmap)> record_fn,
     bool with_data, bool do_open)
 {
@@ -108,7 +108,7 @@ close_error:
         {
             uint64_t read_len = buf_size < dsk.meta_area_size-meta_pos ? buf_size : dsk.meta_area_size-meta_pos;
             read_blocking(dsk.meta_fd, data, read_len);
-            heap->read_blocks(meta_pos-dsk.meta_block_size, read_len, data, [&](heap_object_t *obj)
+            heap->read_blocks(meta_pos-dsk.meta_block_size, read_len, data, [&](heap_entry_t *obj)
             {
                 obj_fn(heap, obj, ((uint8_t*)obj-data+meta_pos)/dsk.meta_block_size);
             }, [](uint32_t, uint32_t, uint8_t*){});
@@ -281,7 +281,7 @@ int disk_tool_t::dump_meta()
             }
             dump_meta_header(hdr);
         },
-        [this](blockstore_heap_t *heap, heap_object_t *obj, uint32_t meta_block_num)
+        [this](blockstore_heap_t *heap, heap_entry_t *obj, uint32_t meta_block_num)
         {
             if (dump_as_old)
                 dump_heap_entry_as_old(heap, obj);
@@ -334,11 +334,10 @@ void disk_tool_t::dump_meta_header(blockstore_meta_header_v3_t *hdr)
     first_entry = true;
 }
 
-void disk_tool_t::dump_heap_entry_as_old(blockstore_heap_t *heap, heap_object_t *obj)
+void disk_tool_t::dump_heap_entry_as_old(blockstore_heap_t *heap, heap_entry_t *obj)
 {
-    heap_write_t *wr = NULL;
-    for (wr = obj->get_writes(); wr && wr->entry_type != (BS_HEAP_BIG_WRITE|BS_HEAP_STABLE) &&
-        wr->entry_type != (BS_HEAP_TOMBSTONE|BS_HEAP_STABLE); wr = wr->next())
+    heap_entry_t *wr = NULL;
+    for (wr = obj; wr && !wr->is_overwrite(); wr = heap->prev(wr))
     {
     }
     if (!wr || wr->entry_type != (BS_HEAP_BIG_WRITE|BS_HEAP_STABLE))
@@ -365,7 +364,7 @@ void disk_tool_t::dump_heap_entry_as_old(blockstore_heap_t *heap, heap_object_t
         printf("%02x", bitmap[i]);
     }
     uint8_t *csums = wr->get_checksums(heap);
-    uint32_t csum_size = wr->get_csum_size(heap);
+    uint32_t csum_size = heap->get_csum_size(wr);
     if (csums)
     {
         printf("\",\"block_csums\":\"");
@@ -382,83 +381,76 @@ void disk_tool_t::dump_heap_entry_as_old(blockstore_heap_t *heap, heap_object_t
     first_entry = false;
 }
 
-void disk_tool_t::dump_heap_entry(blockstore_heap_t *heap, heap_object_t *obj)
+void disk_tool_t::dump_heap_entry(blockstore_heap_t *heap, heap_entry_t *wr)
 {
+    auto t = wr->type();
     printf(
-#define ENTRY_FMT "{\"pool\":%u,\"inode\":\"0x%jx\",\"stripe\":\"0x%jx\",\"writes\":["
+#define ENTRY_FMT "{\"pool\":%u,\"inode\":\"0x%jx\",\"stripe\":\"0x%jx\",\"lsn\":%ju,\"version\":%ju,\"type\":\"%s\",\"stable\":%s"
         (first_entry ? ENTRY_FMT : (",\n" ENTRY_FMT)),
 #undef ENTRY_FMT
-        INODE_POOL(obj->inode), INODE_NO_POOL(obj->inode), obj->stripe
+        INODE_POOL(wr->inode), INODE_NO_POOL(wr->inode), wr->stripe,
+        wr->lsn, wr->version,
+            t == BS_HEAP_BIG_WRITE ? "big" : (
+            t == BS_HEAP_SMALL_WRITE ? "small" : (
+            t == BS_HEAP_INTENT_WRITE ? "intent" : (
+            t == BS_HEAP_DELETE ? "delete" : (
+            t == BS_HEAP_COMMIT ? "commit" : (
+            t == BS_HEAP_ROLLBACK ? "rollback" : (
+            "unknown")))))),
+        (wr->entry_type & BS_HEAP_STABLE) ? "true" : "false"
     );
-    heap_write_t *wr = NULL;
-    bool first_wr = true;
-    for (wr = obj->get_writes(); wr; wr = wr->next())
+    if (t == BS_HEAP_BIG_WRITE)
     {
-        printf(
-#define ENTRY_FMT "{\"lsn\":%ju,\"version\":%ju,\"type\":\"%s\",\"stable\":%s"
-            (first_wr ? ENTRY_FMT : ("," ENTRY_FMT)),
-#undef ENTRY_FMT
-            wr->lsn, wr->version, (wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_SMALL_WRITE ? "small" : (
-                (wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_BIG_WRITE ? "big" : (
-                (wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_INTENT_WRITE ? "intent" : (
-                (wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_TOMBSTONE ? "tombstone" : "unknown"))),
-            (wr->entry_type & BS_HEAP_STABLE) ? "true" : "false"
-        );
-        if ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_BIG_WRITE)
-        {
-            printf(",\"location\":%ju", wr->big_location(heap));
-        }
-        else if ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_INTENT_WRITE)
-        {
-            printf(",\"offset\":%u,\"len\":%u", wr->small().offset, wr->small().len);
-        }
-        else if ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_SMALL_WRITE)
-        {
-            if (!dump_with_data)
-            {
-                printf(",\"offset\":%u,\"len\":%u,\"location\":%ju", wr->small().offset, wr->small().len, wr->small().location);
-            }
-            else
-            {
-                printf(",\"data\":\"");
-                for (uint32_t i = 0; i < wr->small().len; i++)
-                    printf("%02x", buffer_area[wr->small().location + i]);
-                printf("\"");
-            }
-        }
-        uint8_t* bitmap = wr->get_int_bitmap(heap);
-        if (bitmap)
-        {
-            printf(",\"bitmap\":\"");
-            for (uint64_t i = 0; i < dsk.clean_entry_bitmap_size; i++)
-                printf("%02x", bitmap[i]);
-            printf("\"");
-        }
-        bitmap = wr->get_ext_bitmap(heap);
-        if (bitmap)
-        {
-            printf(",\"ext_bitmap\":\"");
-            for (uint64_t i = 0; i < dsk.clean_entry_bitmap_size; i++)
-                printf("%02x", bitmap[i]);
-            printf("\"");
-        }
-        uint8_t *csums = wr->get_checksums(heap);
-        if (csums)
-        {
-            printf(",\"block_csums\":\"");
-            uint32_t csum_size = wr->get_csum_size(heap);
-            for (uint32_t i = 0; i < csum_size; i++)
-                printf("%02x", csums[i]);
-            printf("\"");
-        }
-        if (wr->get_checksum(heap))
-        {
-            printf(",\"data_crc32c\":\"%08x\"", *wr->get_checksum(heap));
-        }
-        printf("}");
-        first_wr = false;
+        printf(",\"location\":%ju", wr->big_location(heap));
     }
-    printf("]}");
+    else if (t == BS_HEAP_INTENT_WRITE)
+    {
+        printf(",\"offset\":%u,\"len\":%u", wr->small().offset, wr->small().len);
+    }
+    else if (t == BS_HEAP_SMALL_WRITE)
+    {
+        if (!dump_with_data)
+        {
+            printf(",\"offset\":%u,\"len\":%u,\"location\":%ju", wr->small().offset, wr->small().len, wr->small().location);
+        }
+        else
+        {
+            printf(",\"data\":\"");
+            for (uint32_t i = 0; i < wr->small().len; i++)
+                printf("%02x", buffer_area[wr->small().location + i]);
+            printf("\"");
+        }
+    }
+    uint8_t* bitmap = wr->get_int_bitmap(heap);
+    if (bitmap)
+    {
+        printf(",\"bitmap\":\"");
+        for (uint64_t i = 0; i < dsk.clean_entry_bitmap_size; i++)
+            printf("%02x", bitmap[i]);
+        printf("\"");
+    }
+    bitmap = wr->get_ext_bitmap(heap);
+    if (bitmap)
+    {
+        printf(",\"ext_bitmap\":\"");
+        for (uint64_t i = 0; i < dsk.clean_entry_bitmap_size; i++)
+            printf("%02x", bitmap[i]);
+        printf("\"");
+    }
+    uint8_t *csums = wr->get_checksums(heap);
+    if (csums)
+    {
+        printf(",\"block_csums\":\"");
+        uint32_t csum_size = heap->get_csum_size(wr);
+        for (uint32_t i = 0; i < csum_size; i++)
+            printf("%02x", csums[i]);
+        printf("\"");
+    }
+    if (wr->get_checksum(heap))
+    {
+        printf(",\"data_crc32c\":\"%08x\"", *wr->get_checksum(heap));
+    }
+    printf("}");
     first_entry = false;
 }
 
@@ -603,101 +595,127 @@ int disk_tool_t::write_json_heap(json11::Json meta, json11::Json journal)
     }
     uint64_t total_used_space = 0;
     uint32_t used_space = 0;
+    uint64_t meta_offset = 0;
+    // FIXME: Rather ugly. Remove the dependency on dsk from heap?
+    blockstore_disk_t dsk;
+    dsk.bitmap_granularity = new_meta_hdr->bitmap_granularity;
+    dsk.block_count = 16;
+    dsk.data_block_size = new_meta_hdr->data_block_size;
+    dsk.clean_entry_bitmap_size = new_clean_entry_bitmap_size;
+    dsk.csum_block_size = new_meta_hdr->csum_block_size;
+    dsk.data_csum_type = new_meta_hdr->data_csum_type;
+    dsk.journal_len = 4096;
+    dsk.meta_area_size = new_meta_len;
+    dsk.meta_block_size = new_meta_hdr->meta_block_size;
+    blockstore_heap_t heap(&dsk, NULL, 0);
+    heap_entry_t *wr = NULL;
+    auto get_wr = [&](uint32_t entry_size)
+    {
+        if (used_space > new_meta_hdr->meta_block_size-entry_size)
+        {
+            if (used_space < new_meta_hdr->meta_block_size-2)
+            {
+                *((uint16_t*)(new_meta_buf + meta_offset + used_space)) = FREE_SPACE_BIT | (uint16_t)(new_meta_hdr->meta_block_size-used_space);
+            }
+            meta_offset += new_meta_hdr->meta_block_size;
+            used_space = 0;
+            if (meta_offset >= new_meta_len)
+            {
+                fprintf(stderr, "Metadata doesn't fit into the new area (total used space: %ju)\n", total_used_space);
+                return (heap_entry_t*)NULL;
+            }
+        }
+        auto wr = (heap_entry_t*)(new_meta_buf + meta_offset + used_space);
+        used_space += entry_size;
+        return wr;
+    };
     // FIXME: Use a streaming json parser
     if (meta["version"] == "3.0")
     {
         // New format
-        std::vector<uint8_t> object_buf;
-        new_heap = new blockstore_heap_t(&dsk, new_journal_buf, 0);
         for (const auto & meta_entry: meta["entries"].array_items())
         {
-            bool invalid = false;
             object_id oid = {
                 .inode = (sscanf_json(NULL, meta_entry["pool"]) << (64-POOL_ID_BITS)) | sscanf_json(NULL, meta_entry["inode"]),
                 .stripe = sscanf_json(NULL, meta_entry["stripe"]),
             };
-            object_buf.clear();
-            object_buf.resize(sizeof(heap_object_t));
-            heap_object_t *obj = (heap_object_t*)object_buf.data();
-            obj->size = sizeof(heap_object_t);
-            obj->write_pos = meta_entry["writes"].array_items().size() ? sizeof(heap_object_t) : 0;
-            obj->entry_type = BS_HEAP_OBJECT;
-            obj->inode = oid.inode;
-            obj->stripe = oid.stripe;
-            size_t pos = sizeof(heap_object_t);
-            heap_write_t *last_wr = NULL;
-            for (auto & write_entry: meta_entry["writes"].array_items())
+            uint32_t wr_type = 0;
+            if (meta_entry["type"] == "small")
+                wr_type = BS_HEAP_SMALL_WRITE;
+            else if (meta_entry["type"] == "intent")
+                wr_type = BS_HEAP_INTENT_WRITE;
+            else if (meta_entry["type"] == "big")
+                wr_type = BS_HEAP_BIG_WRITE;
+            else if (meta_entry["type"] == "delete")
+                wr_type = BS_HEAP_DELETE;
+            else if (meta_entry["type"] == "commit")
+                wr_type = BS_HEAP_COMMIT;
+            else if (meta_entry["type"] == "rollback")
+                wr_type = BS_HEAP_ROLLBACK;
+            else
             {
-                object_buf.resize(object_buf.size() + new_heap->get_max_write_entry_size());
-                heap_write_t *wr = (heap_write_t*)(object_buf.data() + pos);
-                last_wr = wr;
-                uint8_t wr_type = 0;
-                if (write_entry["type"] == "small")
-                    wr_type = BS_HEAP_SMALL_WRITE;
-                else if (write_entry["type"] == "intent")
-                    wr_type = BS_HEAP_INTENT_WRITE;
-                else if (write_entry["type"] == "big")
-                    wr_type = BS_HEAP_BIG_WRITE;
-                else if (write_entry["type"] == "tombstone")
-                    wr_type = BS_HEAP_TOMBSTONE;
-                else
+                fprintf(stderr, "Write entry in %s has invalid type: %s, skipping\n", meta_entry.dump().c_str(), meta_entry["type"].dump().c_str());
+close_err0:
+                free(new_meta_buf);
+                new_meta_buf = NULL;
+                return 1;
+            }
+            uint64_t wr_offset = meta_entry["offset"].uint64_value();
+            uint64_t wr_len = meta_entry["len"].uint64_value();
+            uint32_t wr_size = (wr_type == BS_HEAP_SMALL_WRITE || wr_type == BS_HEAP_INTENT_WRITE
+                ? heap.get_small_entry_size(wr_offset, wr_len)
+                : (wr_type == BS_HEAP_BIG_WRITE ? heap.get_big_entry_size() : heap.get_simple_entry_size()));
+            if (!(wr = get_wr(wr_size)))
+                goto close_err0;
+            wr->inode = oid.inode;
+            wr->stripe = oid.stripe;
+            wr->entry_type = wr_type | (meta_entry["stable"].bool_value() ? BS_HEAP_STABLE : 0);
+            wr->lsn = meta_entry["lsn"].uint64_value();
+            wr->version = meta_entry["version"].uint64_value();
+            wr->size = wr->get_size(&heap);
+            if (wr_type == BS_HEAP_SMALL_WRITE || wr_type == BS_HEAP_INTENT_WRITE)
+            {
+                wr->small().offset = wr_offset;
+                wr->small().len = wr_len;
+                wr->small().location = meta_entry["location"].uint64_value();
+                if (wr_type == BS_HEAP_SMALL_WRITE && meta_entry["data"].is_string() && wr->small().len > 0)
                 {
-                    fprintf(stderr, "Write entry in %s has invalid type: %s, skipping object\n", meta_entry.dump().c_str(), write_entry["type"].dump().c_str());
-                    invalid = true;
-                    break;
-                }
-                wr->entry_type = wr_type | (write_entry["stable"].bool_value() ? BS_HEAP_STABLE : 0);
-                wr->lsn = write_entry["lsn"].uint64_value();
-                wr->version = write_entry["version"].uint64_value();
-                wr->size = wr->get_size(new_heap);
-                wr->next_pos = wr->size;
-                if (wr_type == BS_HEAP_SMALL_WRITE || wr_type == BS_HEAP_INTENT_WRITE)
-                {
-                    wr->small().offset = write_entry["offset"].uint64_value();
-                    wr->small().len = write_entry["len"].uint64_value();
-                    wr->small().location = write_entry["location"].uint64_value();
-                    if (wr_type == BS_HEAP_SMALL_WRITE && write_entry["data"].is_string() && wr->small().len > 0)
+                    if (!new_journal_buf)
                     {
-                        if (!new_journal_buf)
-                        {
-                            fprintf(stderr, "Loading small write data requires overwriting buffer area\n");
-                            free_new_meta();
-                            return 1;
-                        }
-                        wr->small().location = new_heap->find_free_buffer_area(wr->small().len);
-                        fromhexstr(write_entry["data"].string_value(), wr->small().len, new_journal_buf + wr->small().location);
+                        fprintf(stderr, "Loading small write data requires overwriting buffer area\n");
+                        free_new_meta();
+                        return 1;
                     }
-                }
-                else if (wr_type == BS_HEAP_BIG_WRITE)
-                {
-                    uint64_t loc = write_entry["location"].uint64_value();
-                    assert(!(loc % dsk.data_block_size));
-                    assert((loc / dsk.data_block_size) < 0xFFFF0000);
-                    wr->set_big_location(new_heap, loc);
-                }
-                if (write_entry["bitmap"].is_string() && wr->get_int_bitmap(new_heap))
-                {
-                    fromhexstr(write_entry["bitmap"].string_value(), new_clean_entry_bitmap_size, wr->get_int_bitmap(new_heap));
-                }
-                if (write_entry["ext_bitmap"].is_string() && wr->get_ext_bitmap(new_heap))
-                {
-                    fromhexstr(write_entry["ext_bitmap"].string_value(), new_clean_entry_bitmap_size, wr->get_ext_bitmap(new_heap));
-                }
-                if (write_entry["block_csums"].is_string() && wr->get_checksums(new_heap))
-                {
-                    fromhexstr(write_entry["block_csums"].string_value(), wr->get_csum_size(new_heap), wr->get_ext_bitmap(new_heap));
-                }
-                if (write_entry["data_crc32c"].is_string() && wr->get_checksum(new_heap))
-                {
-                    *wr->get_checksum(new_heap) = sscanf_json("%jx", write_entry["data_crc32c"]);
+                    wr->small().location = heap.find_free_buffer_area(wr->small().len);
+                    fromhexstr(meta_entry["data"].string_value(), wr->small().len, new_journal_buf + wr->small().location);
                 }
             }
-            if (invalid)
+            else if (wr_type == BS_HEAP_BIG_WRITE)
             {
-                continue;
+                uint64_t loc = meta_entry["location"].uint64_value();
+                assert(!(loc % dsk.data_block_size));
+                assert((loc / dsk.data_block_size) < 0xFFFF0000);
+                wr->set_big_location(&heap, loc);
             }
-            last_wr->next_pos = 0;
-            new_heap->copy_object(obj, NULL);
+            if (meta_entry["bitmap"].is_string() && wr->get_int_bitmap(&heap))
+            {
+                fromhexstr(meta_entry["bitmap"].string_value(), new_clean_entry_bitmap_size, wr->get_int_bitmap(&heap));
+            }
+            if (meta_entry["ext_bitmap"].is_string() && wr->get_ext_bitmap(&heap))
+            {
+                fromhexstr(meta_entry["ext_bitmap"].string_value(), new_clean_entry_bitmap_size, wr->get_ext_bitmap(&heap));
+            }
+            if (meta_entry["block_csums"].is_string() && wr->get_checksums(&heap))
+            {
+                fromhexstr(meta_entry["block_csums"].string_value(), heap.get_csum_size(wr), wr->get_ext_bitmap(&heap));
+            }
+            if (meta_entry["data_crc32c"].is_string() && wr->get_checksum(&heap))
+            {
+                *wr->get_checksum(&heap) = sscanf_json("%jx", meta_entry["data_crc32c"]);
+            }
+            wr->crc32c = wr->calc_crc32c();
+            
+            assert((uint8_t*)wr + wr->size == new_meta_buf + meta_offset + used_space);
         }
     }
     else
@@ -718,82 +736,17 @@ close_err:
         journal = json11::Json();
         // Convert old format to the new format
         uint64_t next_lsn = 0;
-        uint64_t meta_offset = 0;
-        const uint32_t space_per_object = sizeof(heap_object_t) + sizeof(heap_write_t) +
-            new_clean_entry_bitmap_size*2 + new_data_csum_size;
         uint64_t buffer_pos = 0;
-        // FIXME: Rather ugly. Remove the dependency on dsk from heap?
-        blockstore_disk_t dsk;
-        dsk.bitmap_granularity = new_meta_hdr->bitmap_granularity;
-        dsk.block_count = 16;
-        dsk.data_block_size = new_meta_hdr->data_block_size;
-        dsk.clean_entry_bitmap_size = new_clean_entry_bitmap_size;
-        dsk.csum_block_size = new_meta_hdr->csum_block_size;
-        dsk.data_csum_type = new_meta_hdr->data_csum_type;
-        dsk.journal_len = 4096;
-        dsk.meta_area_size = new_meta_len;
-        dsk.meta_block_size = new_meta_hdr->meta_block_size;
-        dsk.meta_block_target_free_space = 800;
-        blockstore_heap_t heap(&dsk, NULL, 0);
         for (const auto & meta_entry: meta["entries"].array_items())
         {
             object_id oid = {
                 .inode = (sscanf_json(NULL, meta_entry["pool"]) << (64-POOL_ID_BITS)) | sscanf_json(NULL, meta_entry["inode"]),
                 .stripe = sscanf_json(NULL, meta_entry["stripe"]),
             };
-            uint32_t space_for_this = space_per_object;
-            auto j_it = journal_by_object.find(oid);
-            if (j_it != journal_by_object.end())
-            {
-                for (auto & rec: j_it->second)
-                {
-                    if (rec["type"] == "small_write" || rec["type"] == "small_write_instant")
-                    {
-                        uint64_t off = rec["offset"].uint64_value();
-                        uint64_t len = rec["len"].uint64_value();
-                        if (off+len > new_meta_hdr->data_block_size)
-                        {
-                            fprintf(stderr, "Journal entry has too large offset or length: %s\n", json11::Json(rec).dump().c_str());
-                            goto close_err;
-                        }
-                        space_for_this += sizeof(heap_write_t) + new_clean_entry_bitmap_size +
-                            ((off+len+new_meta_hdr->csum_block_size-1)/new_meta_hdr->csum_block_size - off/new_meta_hdr->csum_block_size) * (new_meta_hdr->data_csum_type & 0xFF);
-                    }
-                    else /*if (rec["type"] == "big_write" || rec["type"] == "big_write_instant")*/
-                    {
-                        space_for_this += sizeof(heap_write_t) + 2*new_clean_entry_bitmap_size + new_data_csum_size;
-                    }
-                }
-            }
-            if (space_for_this > new_meta_hdr->meta_block_size)
-            {
-                fprintf(stderr, "Object doesn't fit in a single metadata block. Object meta: %s, object journal: %s\n",
-                    meta_entry.dump().c_str(), json11::Json(j_it->second).dump().c_str());
+            if (!(wr = get_wr(heap.get_big_entry_size())))
                 goto close_err;
-            }
-            if (used_space + space_for_this > new_meta_hdr->meta_block_size-dsk.meta_block_target_free_space)
-            {
-                if (used_space < new_meta_hdr->meta_block_size-2)
-                {
-                    *((uint16_t*)(new_meta_buf + meta_offset + used_space)) = FREE_SPACE_BIT | (uint16_t)(new_meta_hdr->meta_block_size-used_space);
-                }
-                meta_offset += new_meta_hdr->meta_block_size;
-                used_space = 0;
-                if (meta_offset >= new_meta_len)
-                {
-                    fprintf(stderr, "Metadata doesn't fit into the new area (total used space: %ju, minimum free space in block: %u/%u)\n",
-                        total_used_space, dsk.meta_block_target_free_space, new_meta_hdr->meta_block_size);
-                    goto close_err;
-                }
-            }
-            heap_object_t *obj = (heap_object_t*)(new_meta_buf + meta_offset + used_space);
-            obj->size = sizeof(heap_object_t);
-            obj->write_pos = sizeof(heap_object_t);
-            obj->entry_type = BS_HEAP_OBJECT;
-            obj->inode = oid.inode;
-            obj->stripe = oid.stripe;
-            heap_write_t *wr = obj->get_writes();
-            wr->next_pos = 0;
+            wr->inode = oid.inode;
+            wr->stripe = oid.stripe;
             wr->entry_type = BS_HEAP_BIG_WRITE|BS_HEAP_STABLE;
             wr->lsn = ++next_lsn;
             wr->version = sscanf_json(NULL, meta_entry["version"]);
@@ -803,17 +756,24 @@ close_err:
             fromhexstr(meta_entry["ext_bitmap"].string_value(), new_clean_entry_bitmap_size, wr->get_ext_bitmap(&heap));
             if (new_meta_hdr->data_csum_type != 0)
                 fromhexstr(meta_entry["data_csum"].string_value(), new_data_csum_size, wr->get_checksums(&heap));
+            wr->crc32c = wr->calc_crc32c();
+            assert((uint8_t*)wr + wr->size == new_meta_buf + meta_offset + used_space);
+            auto j_it = journal_by_object.find(oid);
             if (j_it != journal_by_object.end())
             {
                 for (auto & rec: j_it->second)
                 {
-                    wr->next_pos = wr->get_size(&heap);
-                    wr = wr->next();
-                    wr->next_pos = 0;
-                    wr->lsn = ++next_lsn;
-                    wr->version = rec["ver"].uint64_value();
                     uint64_t wr_offset = rec["offset"].uint64_value();
                     uint64_t wr_len = rec["len"].uint64_value();
+                    if (!(wr = get_wr(rec["type"] == "small_write" || rec["type"] == "small_write_instant"
+                        ? heap.get_small_entry_size(wr_offset, wr_len) : heap.get_big_entry_size())))
+                    {
+                        goto close_err;
+                    }
+                    wr->inode = oid.inode;
+                    wr->stripe = oid.stripe;
+                    wr->lsn = ++next_lsn;
+                    wr->version = rec["ver"].uint64_value();
                     if (rec["type"] == "small_write" || rec["type"] == "small_write_instant")
                     {
                         if (wr_len > 0 && !rec["data"].is_string())
@@ -862,12 +822,10 @@ close_err:
                         assert(0);
                     }
                     wr->size = wr->get_size(&heap);
+                    wr->crc32c = wr->calc_crc32c();
+                    assert((uint8_t*)wr + wr->size == new_meta_buf + meta_offset + used_space);
                 }
             }
-            obj->crc32c = obj->calc_crc32c();
-            assert(((uint8_t*)wr + wr->size - (uint8_t*)obj) == space_for_this);
-            used_space += space_for_this;
-            total_used_space += space_for_this;
         }
         if (used_space > 0 && used_space < new_meta_hdr->meta_block_size-2)
         {
diff --git a/src/disk_tool/disk_tool_resize.cpp b/src/disk_tool/disk_tool_resize.cpp
index 83c9b452..526e8157 100644
--- a/src/disk_tool/disk_tool_resize.cpp
+++ b/src/disk_tool/disk_tool_resize.cpp
@@ -37,9 +37,9 @@ int disk_tool_t::raw_resize()
         {
             resize_init(hdr);
         },
-        [this](blockstore_heap_t *heap, heap_object_t *obj, uint32_t meta_block_num)
+        [this](blockstore_heap_t *heap, heap_entry_t *obj, uint32_t meta_block_num)
         {
-            for (auto wr = obj->get_writes(); wr; wr = wr->next())
+            for (auto wr = obj; wr; wr = heap->prev(wr))
             {
                 if ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_BIG_WRITE)
                 {
@@ -542,7 +542,7 @@ int disk_tool_t::resize_rebuild_meta()
         memset(new_meta_buf, 0, new_meta_len);
         new_meta_hdr = (blockstore_meta_header_v3_t *)new_meta_buf;
     }
-    std::vector<heap_write_t*> writes;
+    std::vector<heap_entry_t*> writes;
     int r = process_meta(
         [&](blockstore_meta_header_v3_t *hdr)
         {
@@ -563,102 +563,91 @@ int disk_tool_t::resize_rebuild_meta()
                 build_journal_start();
             }
         },
-        [&](blockstore_heap_t *heap, heap_object_t *obj, uint32_t meta_block_num)
+        [&](blockstore_heap_t *heap, heap_entry_t *wr, uint32_t meta_block_num)
         {
-            for (auto wr = obj->get_writes(); wr; wr = wr->next())
+            if (wr->type() == BS_HEAP_BIG_WRITE)
             {
-                if ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_BIG_WRITE)
+                uint64_t block_num = wr->big().block_num;
+                auto remap_it = data_remap.find(block_num);
+                if (remap_it != data_remap.end())
+                    block_num = remap_it->second;
+                if (block_num < free_first || block_num >= total_blocks-free_last)
                 {
-                    uint64_t block_num = wr->big().block_num;
-                    auto remap_it = data_remap.find(block_num);
-                    if (remap_it != data_remap.end())
-                        block_num = remap_it->second;
-                    if (block_num < free_first || block_num >= total_blocks-free_last)
-                    {
-                        fprintf(stderr, "BUG: remapped block %ju not in range %ju..%ju\n", block_num, free_first, total_blocks-free_last);
-                        exit(1);
-                    }
-                    block_num += data_idx_diff;
-                    wr->big().block_num = block_num;
-                }
-                else if ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_SMALL_WRITE)
-                {
-                    if (new_heap && wr->small().len > 0)
-                    {
-                        if (new_journal_ptr-new_journal_buf+wr->small().len > new_journal_len)
-                        {
-                            fprintf(stderr, "Small write data doesn't fit into the new buffer area\n");
-                            exit(1);
-                        }
-                        memcpy(new_journal_ptr, buffer_area+wr->small().location, wr->small().len);
-                        wr->small().location = new_journal_ptr-new_journal_buf;
-                        new_journal_ptr += wr->small().len;
-                    }
-                }
-                else if (!new_heap)
-                {
-                    fprintf(stderr, "Object %jx:%jx can't be converted to the old format because it contains %s\n",
-                        obj->inode, obj->stripe, (wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_TOMBSTONE
-                            ? "a tombstone" : ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_INTENT_WRITE ? "an intent_write entry" : "an unknown entry"));
+                    fprintf(stderr, "BUG: remapped block %ju not in range %ju..%ju\n", block_num, free_first, total_blocks-free_last);
                     exit(1);
                 }
+                block_num += data_idx_diff;
+                wr->big().block_num = block_num;
+            }
+            else if (wr->type() == BS_HEAP_SMALL_WRITE)
+            {
+                if (new_heap && wr->small().len > 0)
+                {
+                    if (new_journal_ptr-new_journal_buf+wr->small().len > new_journal_len)
+                    {
+                        fprintf(stderr, "Small write data doesn't fit into the new buffer area\n");
+                        exit(1);
+                    }
+                    memcpy(new_journal_ptr, buffer_area+wr->small().location, wr->small().len);
+                    wr->small().location = new_journal_ptr-new_journal_buf;
+                    new_journal_ptr += wr->small().len;
+                }
+            }
+            // FIXME skip BS_HEAP_DELETE
+            else if (!new_heap)
+            {
+                fprintf(stderr, "Object %jx:%jx can't be converted to the old format because it contains %s\n",
+                    wr->inode, wr->stripe, ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_INTENT_WRITE ? "an intent_write entry" : "an unknown entry"));
+                exit(1);
             }
             if (new_heap)
             {
                 // New -> New
-                new_heap->copy_object(obj, NULL);
+                //new_heap->copy_object(obj, NULL);
             }
             else
             {
                 // Fill journal
-                writes.clear();
-                for (auto wr = obj->get_writes(); wr; wr = wr->next())
+                // It should be done in order
+                assert((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_SMALL_WRITE || wr->entry_type == BS_HEAP_BIG_WRITE);
+                uint32_t je_size = ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_SMALL_WRITE
+                    ? sizeof(journal_entry_small_write) + dsk.dirty_dyn_size(wr->small().offset, wr->small().len)
+                    : sizeof(journal_entry_big_write) + dsk.dirty_dyn_size(0, dsk.data_block_size));
+                choose_journal_block(je_size);
+                journal_entry *je = (journal_entry*)(new_journal_ptr + new_journal_in_pos);
+                je->magic = JOURNAL_MAGIC;
+                je->type = (wr->entry_type & BS_HEAP_STABLE) ? JE_SMALL_WRITE_INSTANT : JE_SMALL_WRITE;
+                je->size = je_size;
+                je->crc32_prev = new_crc32_prev;
+                je->small_write.oid = (object_id){ .inode = wr->inode, .stripe = wr->stripe };
+                je->small_write.version = wr->version;
+                if (wr->type() == BS_HEAP_SMALL_WRITE)
                 {
-                    writes.push_back(wr);
+                    je->small_write.offset = wr->small().offset;
+                    je->small_write.len = wr->small().len;
+                    je->small_write.data_offset = new_journal_data-new_journal_buf;
+                    if (je->small_write.data_offset + je->small_write.len > new_journal_len)
+                    {
+                        fprintf(stderr, "Error: live entries don't fit to the new journal\n");
+                        exit(1);
+                    }
+                    memcpy(new_journal_data, buffer_area+wr->small().location, je->small_write.len);
+                    new_journal_data += je->small_write.len;
+                    if (dsk.data_csum_type == 0 && wr->get_checksum(heap))
+                        je->small_write.crc32_data = *wr->get_checksum(heap);
                 }
-                for (ssize_t i = writes.size()-2; i >= 0; i--)
+                else
                 {
-                    auto wr = writes[i];
-                    assert((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_SMALL_WRITE || wr->entry_type == BS_HEAP_BIG_WRITE);
-                    uint32_t je_size = ((wr->entry_type & BS_HEAP_TYPE) == BS_HEAP_SMALL_WRITE
-                        ? sizeof(journal_entry_small_write) + dsk.dirty_dyn_size(wr->small().offset, wr->small().len)
-                        : sizeof(journal_entry_big_write) + dsk.dirty_dyn_size(0, dsk.data_block_size));
-                    choose_journal_block(je_size);
-                    journal_entry *je = (journal_entry*)(new_journal_ptr + new_journal_in_pos);
-                    je->magic = JOURNAL_MAGIC;
-                    je->type = (wr->entry_type & BS_HEAP_STABLE) ? JE_SMALL_WRITE_INSTANT : JE_SMALL_WRITE;
-                    je->size = je_size;
-                    je->crc32_prev = new_crc32_prev;
-                    je->small_write.oid = (object_id){ .inode = obj->inode, .stripe = obj->stripe };
-                    je->small_write.version = wr->version;
-                    if (wr->type() == BS_HEAP_SMALL_WRITE)
-                    {
-                        je->small_write.offset = wr->small().offset;
-                        je->small_write.len = wr->small().len;
-                        je->small_write.data_offset = new_journal_data-new_journal_buf;
-                        if (je->small_write.data_offset + je->small_write.len > new_journal_len)
-                        {
-                            fprintf(stderr, "Error: live entries don't fit to the new journal\n");
-                            exit(1);
-                        }
-                        memcpy(new_journal_data, buffer_area+wr->small().location, je->small_write.len);
-                        new_journal_data += je->small_write.len;
-                        if (dsk.data_csum_type == 0 && wr->get_checksum(heap))
-                            je->small_write.crc32_data = *wr->get_checksum(heap);
-                    }
-                    else
-                    {
-                        je->big_write.location = wr->big_location(heap);
-                    }
-                    memcpy((uint8_t*)je + je->size, wr->get_ext_bitmap(heap), new_clean_entry_bitmap_size);
-                    if (dsk.data_csum_type != 0 && wr->get_checksums(heap))
-                    {
-                        memcpy((uint8_t*)je + je->size + new_clean_entry_bitmap_size, wr->get_checksums(heap), wr->get_csum_size(heap));
-                    }
-                    je->crc32 = je_crc32(je);
-                    new_journal_in_pos += je->size;
-                    new_crc32_prev = je->crc32;
+                    je->big_write.location = wr->big_location(heap);
                 }
+                memcpy((uint8_t*)je + je->size, wr->get_ext_bitmap(heap), new_clean_entry_bitmap_size);
+                if (dsk.data_csum_type != 0 && wr->get_checksums(heap))
+                {
+                    memcpy((uint8_t*)je + je->size + new_clean_entry_bitmap_size, wr->get_checksums(heap), heap->get_csum_size(wr));
+                }
+                je->crc32 = je_crc32(je);
+                new_journal_in_pos += je->size;
+                new_crc32_prev = je->crc32;
                 // New -> Old
                 if (writes[writes.size()-1]->entry_type == BS_HEAP_BIG_WRITE|BS_HEAP_STABLE)
                 {
@@ -667,7 +656,7 @@ int disk_tool_t::resize_rebuild_meta()
                     clean_disk_entry *new_entry = (clean_disk_entry*)(new_meta_buf + dsk.meta_block_size +
                         dsk.meta_block_size*(block_num / new_entries_per_block) +
                         new_clean_entry_size*(block_num % new_entries_per_block));
-                    new_entry->oid = (object_id){ .inode = obj->inode, .stripe = obj->stripe };
+                    new_entry->oid = (object_id){ .inode = wr->inode, .stripe = wr->stripe };
                     new_entry->version = big_wr->version;
                     memcpy(new_entry->bitmap, big_wr->get_ext_bitmap(heap), new_clean_entry_bitmap_size);
                     memcpy(new_entry->bitmap + new_clean_entry_bitmap_size, big_wr->get_int_bitmap(heap), new_clean_entry_bitmap_size);
@@ -691,11 +680,12 @@ int disk_tool_t::resize_rebuild_meta()
             if (new_heap)
             {
                 // Old -> New
-                uint8_t wr_buf[new_heap->get_max_write_entry_size()];
-                heap_write_t *wr = (heap_write_t*)wr_buf;
+                heap_entry_t *wr = NULL;
                 wr->entry_type = BS_HEAP_BIG_WRITE|BS_HEAP_STABLE;
+                wr->inode = entry->oid.inode;
+                wr->stripe = entry->oid.stripe;
+                wr->version = entry->version;
                 wr->big().block_num = block_num;
-                wr->next_pos = 0;
                 wr->size = wr->get_size(new_heap);
                 if (bitmap)
                 {
@@ -703,7 +693,7 @@ int disk_tool_t::resize_rebuild_meta()
                     memcpy(wr->get_int_bitmap(new_heap), bitmap+new_clean_entry_bitmap_size, new_clean_entry_bitmap_size);
                     memcpy(wr->get_checksums(new_heap), bitmap+2*new_clean_entry_bitmap_size, new_data_csum_size);
                 }
-                new_heap->post_write(entry->oid, wr, NULL, NULL);
+                // FIXME add
             }
             else
             {
diff --git a/src/test/ringloop_mock.cpp b/src/test/ringloop_mock.cpp
index 336d1a38..fc718bb0 100644
--- a/src/test/ringloop_mock.cpp
+++ b/src/test/ringloop_mock.cpp
@@ -171,6 +171,7 @@ disk_mock_t::disk_mock_t(size_t size, bool buffered)
     this->size = size;
     this->data = (uint8_t*)malloc_or_die(size);
     this->buffered = buffered;
+    memset(this->data, 0, size);
 }
 
 disk_mock_t::~disk_mock_t()
@@ -238,16 +239,18 @@ void disk_mock_t::clear(size_t offset, size_t len)
 
 void disk_mock_t::discard_buffers(bool all, uint32_t seed)
 {
-    if (trace)
-        printf("disk: discard buffers all=%d seed=%u\n", all, seed);
     if (all)
     {
+        if (trace)
+            printf("disk: discard all buffers (%zu)\n", buffers.size());
         for (auto & b: buffers)
             free(b.second.iov_base);
         buffers.clear();
     }
     else
     {
+        if (trace)
+            printf("disk: discard random buffers seed=%u\n", seed);
         std::mt19937 rnd(seed);
         for (auto it = buffers.begin(); it != buffers.end(); )
         {
diff --git a/src/test/test_blockstore.cpp b/src/test/test_blockstore.cpp
index ef4836bb..3faa975b 100644
--- a/src/test/test_blockstore.cpp
+++ b/src/test/test_blockstore.cpp
@@ -240,12 +240,14 @@ static void test_fsync(bool separate_meta)
     if (separate_meta)
     {
         test.config["meta_device"] = "./test_meta.bin";
-        test.config["disable_meta_fsync"] = "1";
+        test.config["disable_meta_fsync"] = "0";
         test.config["meta_device_size"] = "33554432";
         test.config["meta_device_sect"] = "4096";
         test.config["data_offset"] = "0";
     }
     test.init();
+    if (test.meta_disk)
+        test.meta_disk->trace = 1;
 
     // Write
     printf("writing\n");
@@ -263,7 +265,10 @@ static void test_fsync(bool separate_meta)
     // Destroy and restart without sync
     printf("destroying\n");
     test.destroy_bs();
-    test.data_disk->discard_buffers(true, 0);
+    if (separate_meta)
+        test.meta_disk->discard_buffers(true, 0);
+    else
+        test.data_disk->discard_buffers(true, 0);
     test.init();
 
     // Check ENOENT
@@ -292,7 +297,10 @@ static void test_fsync(bool separate_meta)
     // Discard and restart again
     printf("destroying again\n");
     test.destroy_bs();
-    test.data_disk->discard_buffers(true, 0);
+    if (separate_meta)
+        test.meta_disk->discard_buffers(true, 0);
+    else
+        test.data_disk->discard_buffers(true, 0);
     test.init();
 
     // Check that it's present now
@@ -353,7 +361,7 @@ static void test_padded_csum_intent(bool perfect)
     // Write
     printf("writing\n");
     blockstore_op_t op;
-    op.opcode = BS_OP_WRITE;
+    op.opcode = BS_OP_WRITE_STABLE;
     op.oid = { .inode = 1, .stripe = 0 };
     op.version = 1;
     op.offset = 8192;
@@ -386,36 +394,16 @@ static void test_padded_csum_intent(bool perfect)
     test.exec_op(&op);
     assert(op.retval == op.len);
 
-    // Write again (small because uncompactable)
-    printf("writing (small)\n");
-    op.version = 3;
-    op.offset = 60*1024;
-    memset(op.buf, 0xcc, 4096);
-    test.exec_op(&op);
-    assert(op.retval == op.len);
-
-    // Check that these are really big+intent+small writes
+    // Check that these are really big+intent writes
     // (intent is not collapsible because of csum_block_size > bitmap_granularity)
-    heap_object_t *obj = test.bs->heap->read_entry((object_id){ .inode = 1, .stripe = 0 }, NULL);
-    assert(obj);
-    assert(obj->get_writes()->next());
-    assert(obj->get_writes()->next()->next());
-    assert(!obj->get_writes()->next()->next()->next());
-    assert(obj->get_writes()->entry_type == BS_HEAP_SMALL_WRITE);
-    assert(obj->get_writes()->next()->entry_type == (perfect ? BS_HEAP_SMALL_WRITE : BS_HEAP_INTENT_WRITE));
-    assert(obj->get_writes()->next()->next()->entry_type == BS_HEAP_BIG_WRITE);
-
-    // Commit
-    printf("commit version 3\n");
-    op.opcode = BS_OP_STABLE;
-    op.len = 1;
-    *((obj_ver_id*)op.buf) = {
-        .oid = { .inode = 1, .stripe = 0 },
-        .version = 3,
-    };
-    test.exec_op(&op);
-    assert(op.retval == 0);
-    assert(test.bs->heap->get_compact_queue_size());
+    heap_entry_t *obj = test.bs->heap->read_entry((object_id){ .inode = 1, .stripe = 0 });
+    auto wr = obj;
+    assert(wr);
+    assert(wr->entry_type == (perfect ? BS_HEAP_SMALL_WRITE : BS_HEAP_INTENT_WRITE) | BS_HEAP_STABLE);
+    wr = test.bs->heap->prev(wr);
+    assert(wr);
+    assert(wr->entry_type == BS_HEAP_BIG_WRITE|BS_HEAP_STABLE);
+    assert(!test.bs->heap->prev(wr));
 
     // Trigger & wait compaction
     test.bs->flusher->request_trim();
@@ -436,12 +424,10 @@ static void test_padded_csum_intent(bool perfect)
     assert(memcheck(op2.buf+8*1024, 0xaa, 4*1024));
     assert(memcheck(op2.buf+12*1024, 0, 16*1024));
     assert(memcheck(op2.buf+28*1024, 0xbb, 4*1024));
-    assert(memcheck(op2.buf+32*1024, 0, 28*1024));
-    assert(memcheck(op2.buf+60*1024, 0xcc, 4*1024));
-    assert(memcheck(op2.buf+64*1024, 0, 64*1024));
+    assert(memcheck(op2.buf+32*1024, 0, 96*1024));
 
-    obj = test.bs->heap->read_entry((object_id){ .inode = 1, .stripe = 0 }, NULL);
-    assert(!obj->get_writes()->next());
+    obj = test.bs->heap->read_entry((object_id){ .inode = 1, .stripe = 0 });
+    assert(!test.bs->heap->prev(obj));
 
     free(op.buf);
     free(op2.buf);