6.16-stable review patch. If anyone has any objections, please let me know.
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From: Boris Burkov boris@bur.io
commit de134cb54c3a67644ff95b1c9bffe545e752c912 upstream.
The following workload on a squota enabled fs:
btrfs subvol create mnt/subvol
# ensure subvol extents get accounted sync btrfs qgroup create 1/1 mnt btrfs qgroup assign mnt/subvol 1/1 mnt btrfs qgroup delete mnt/subvol
# make the cleaner thread run btrfs filesystem sync mnt sleep 1 btrfs filesystem sync mnt btrfs qgroup destroy 1/1 mnt
will fail with EBUSY. The reason is that 1/1 does the quick accounting when we assign subvol to it, gaining its exclusive usage as excl and excl_cmpr. But then when we delete subvol, the decrement happens via record_squota_delta() which does not update excl_cmpr, as squotas does not make any distinction between compressed and normal extents. Thus, we increment excl_cmpr but never decrement it, and are unable to delete 1/1. The two possible fixes are to make squota always mirror excl and excl_cmpr or to make the fast accounting separately track the plain and cmpr numbers. The latter felt cleaner to me so that is what I opted for.
Fixes: 1e0e9d5771c3 ("btrfs: add helper for recording simple quota deltas") CC: stable@vger.kernel.org # 6.12+ Reviewed-by: Qu Wenruo wqu@suse.com Signed-off-by: Boris Burkov boris@bur.io Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/qgroup.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1483,6 +1483,7 @@ static int __qgroup_excl_accounting(stru struct btrfs_qgroup *qgroup; LIST_HEAD(qgroup_list); u64 num_bytes = src->excl; + u64 num_bytes_cmpr = src->excl_cmpr; int ret = 0;
qgroup = find_qgroup_rb(fs_info, ref_root); @@ -1494,11 +1495,12 @@ static int __qgroup_excl_accounting(stru struct btrfs_qgroup_list *glist;
qgroup->rfer += sign * num_bytes; - qgroup->rfer_cmpr += sign * num_bytes; + qgroup->rfer_cmpr += sign * num_bytes_cmpr;
WARN_ON(sign < 0 && qgroup->excl < num_bytes); + WARN_ON(sign < 0 && qgroup->excl_cmpr < num_bytes_cmpr); qgroup->excl += sign * num_bytes; - qgroup->excl_cmpr += sign * num_bytes; + qgroup->excl_cmpr += sign * num_bytes_cmpr;
if (sign > 0) qgroup_rsv_add_by_qgroup(fs_info, qgroup, src);