Btrfs: fix racy system chunk allocation when setting block group ro
If while setting a block group read-only we end up allocating a system
chunk, through check_system_chunk(), we were not doing it while holding
the chunk mutex which is a problem if a concurrent chunk allocation is
happening, through do_chunk_alloc(), as it means both block groups can
end up using the same logical addresses and physical regions in the
device(s). So make sure we hold the chunk mutex.
Cc: stable@vger.kernel.org # 4.0+
Fixes: 2f0810880f08 ("btrfs: delete chunk allocation attemp when
setting block group ro")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 96aebf3..174f5e1 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4625,6 +4625,7 @@
{
u64 chunk_offset;
+ ASSERT(mutex_is_locked(&extent_root->fs_info->chunk_mutex));
chunk_offset = find_next_chunk(extent_root->fs_info);
return __btrfs_alloc_chunk(trans, extent_root, chunk_offset, type);
}