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Btrfs: fix racy system chunk allocation when setting block group ro

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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: 2f0810880f ("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>
This commit is contained in:
Filipe Manana
2015-05-18 19:11:40 +01:00
committed by Chris Mason
parent 2c2ed5aa01
commit a96295965b
2 changed files with 3 additions and 0 deletions
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2
fs/btrfs/extent-tree.c
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@@ -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);