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Implement CAS writes

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From now on, reads will return the server-side object version numbers
and writes and deletes will have an additional "version" parameter
which, if set to a non-zero value, will be atomically compared with
the current version of the object plus 1 and the modification will
fail if it doesn't match.

This feature opens the road to correct online flattening of snapshot
layers and other interesting things.
This commit is contained in:
Vitaliy Filippov
2021-06-15 00:12:35 +03:00
parent f9fe72d40a
commit 891250d355
7 changed files with 55 additions and 10 deletions
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src/osd_primary_chain.cpp
+12 -2
View File
@@ -65,7 +65,10 @@ int osd_t::read_bitmaps(osd_op_t *cur_op, pg_t & pg, int base_state)
auto vo_it = pg.ver_override.find(cur_oid);
auto read_version = (vo_it != pg.ver_override.end() ? vo_it->second : UINT64_MAX);
// Read bitmap synchronously from the local database
bs->read_bitmap(cur_oid, read_version, op_data->snapshot_bitmaps + chain_num*clean_entry_bitmap_size, NULL);
bs->read_bitmap(
cur_oid, read_version, op_data->snapshot_bitmaps + chain_num*clean_entry_bitmap_size,
!chain_num ? &cur_op->reply.rw.version : NULL
);
}
}
else
@@ -228,7 +231,10 @@ int osd_t::submit_bitmap_subops(osd_op_t *cur_op, pg_t & pg)
// Read bitmap synchronously from the local database
for (int j = prev; j <= i; j++)
{
bs->read_bitmap((*bitmap_requests)[j].oid, (*bitmap_requests)[j].version, (*bitmap_requests)[j].bmp_buf, NULL);
bs->read_bitmap(
(*bitmap_requests)[j].oid, (*bitmap_requests)[j].version, (*bitmap_requests)[j].bmp_buf,
(*bitmap_requests)[j].oid.inode == cur_op->req.rw.inode ? &cur_op->reply.rw.version : NULL
);
}
}
else
@@ -264,6 +270,10 @@ int osd_t::submit_bitmap_subops(osd_op_t *cur_op, pg_t & pg)
for (int j = prev; j <= i; j++)
{
memcpy((*bitmap_requests)[j].bmp_buf, cur_buf, clean_entry_bitmap_size);
if ((*bitmap_requests)[j].oid.inode == cur_op->req.rw.inode)
{
memcpy(&cur_op->reply.rw.version, cur_buf-8, 8);
}
cur_buf += 8 + clean_entry_bitmap_size;
}
}