Commit a9629596 authored May 18, 2015 by Filipe Manana Committed by Chris Mason May 19, 2015

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: 2f081088 ("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>

parent 2c2ed5aa

fs/btrfs/extent-tree.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -8842,7 +8842,9 @@ again:
		out:
		if (cache->flags & BTRFS_BLOCK_GROUP_SYSTEM) {
		alloc_flags = update_block_group_flags(root, cache->flags);
		lock_chunks(root->fs_info->chunk_root);
		check_system_chunk(trans, root, alloc_flags);
		unlock_chunks(root->fs_info->chunk_root);
		}
		mutex_unlock(&root->fs_info->ro_block_group_mutex);

fs/btrfs/volumes.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -4625,6 +4625,7 @@ int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
		{
		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);
		}

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