[PATCH] btrfs: zoned: catch aborted trans in btrfs_zoned_reserve_data_reloc_bg

[Johannes Thumshirn <johannes.thumshirn@wdc.com>]

btrfs_zoned_reserve_data_reloc_bg() is called on each mount of a file
system and allocates a new block-group, to assign it to be the dedicated
relocation target, if no pre-existing usable block-group for this task is
found.

If for some reason the transaction was aborted during the call to
btrfs_chunk_alloc() and btrfs_end_transaction() is executed, a
NULL-pointer dereference happens in btrfs_end_transaction().

Check if the transaction was aborted before calling into
btrfs_end_transaction() and if it was aborted return early.

Fixes: 694ce5e143d6 ("btrfs: zoned: reserve data_reloc block group on mount")
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 fs/btrfs/zoned.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index f64b872d53ce..265947fde727 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -2842,6 +2842,9 @@ void btrfs_zoned_reserve_data_reloc_bg(struct btrfs_fs_info *fs_info)
 	ASSERT(space_info->subgroup_id == BTRFS_SUB_GROUP_DATA_RELOC,
 	       "space_info->subgroup_id=%d", space_info->subgroup_id);
 	ret = btrfs_chunk_alloc(trans, space_info, alloc_flags, CHUNK_ALLOC_FORCE);
+	if (TRANS_ABORTED(trans))
+		return;
+
 	btrfs_end_transaction(trans);
 	if (ret == 1) {
 		/*
-- 
2.53.0