[PATCH] ext4: fix quota accounting WARN in bigalloc punch hole

[Qiliang Yuan]

When doing direct I/O write on a bigalloc filesystem, the allocated
extent might not cover entire clusters at its boundaries, leaving
delayed blocks in those boundary clusters.  In ext4_es_insert_extent(),
__revise_pending() inserts new pending reservations for those boundary
clusters, and the return value (pending=true) was added to resv_used,
causing ext4_da_update_reserve_space() to incorrectly release the
quota reservations for those boundary clusters.

Later when PUNCH_HOLE removes the DIO-allocated blocks, the
extent removal path detects the pending reservation via
ext4_is_pending() and calls ext4_rereserve_cluster().  This tries
to reclaim quota from dq_dqb.dqb_curspace back to dqb_rsvspace,
but since the quota was already incorrectly released, dqb_curspace
is insufficient, triggering:

  WARNING at dquot_reclaim_space_nodirty+0x77c/0x8c0

The subsequent delalloc writeback then fires a second WARN from
dquot_claim_space_nodirty() for the same reason: dqb_rsvspace was
depleted by the earlier incorrect release.

__es_remove_extent() -> get_rsvd() already correctly excludes
boundary clusters that still contain delayed blocks from resv_used.
Adding pending to resv_used double-counts those boundary clusters,
erroneously releasing reservations that are still needed.

Remove the pending variable and the resv_used += pending addition.

Fixes: c543e2429640 ("ext4: update delalloc data reserve spcae in ext4_es_insert_extent()")
Reported-by: Zijing Yin <yzjaurora@xxxxxxxxx>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221570
Signed-off-by: Qiliang Yuan <realwujing@xxxxxxxxx>
---
 fs/ext4/extents_status.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 6e4a191e82191..fefe0bb8ac4d1 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -909,7 +909,7 @@ void ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
 	struct extent_status newes;
 	ext4_lblk_t end = lblk + len - 1;
 	int err1 = 0, err2 = 0, err3 = 0;
-	int resv_used = 0, pending = 0;
+	int resv_used = 0;
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	struct extent_status *es1 = NULL;
 	struct extent_status *es2 = NULL;
@@ -977,7 +977,6 @@ void ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
 			__free_pending(pr);
 			pr = NULL;
 		}
-		pending = err3;
 	}
 	ext4_es_inc_seq(inode);
 error:
@@ -998,7 +997,6 @@ void ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
 	 * any previously delayed allocated clusters instead of claim them
 	 * again.
 	 */
-	resv_used += pending;
 	if (resv_used)
 		ext4_da_update_reserve_space(inode, resv_used,
 					     delalloc_reserve_used);

---
base-commit: eb3f4b7426cfd2b79d65b7d37155480b32259a11
change-id: 20260528-fix-ext4-bigalloc-punch-hole-quota-v2-2adca315d1ba

Best regards,
-- 
Qiliang Yuan <realwujing@xxxxxxxxx>