FAILED: patch "[PATCH] xfs: strengthen the "is cow staging" helpers in scrub" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 0d43368844a75ad13561a1198a3b027940730756
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026091607-platonic-empathic-c32b@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0d43368844a75ad13561a1198a3b027940730756 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <[email protected]>
Date: Wed, 2 Sep 2026 22:51:36 -0700
Subject: [PATCH] xfs: strengthen the "is cow staging" helpers in scrub

LOLLM pointed out a bug in both of the refcount scrub predicates that determine if a range of blocks is marked as CoW staging in the btree. While it compares blockcount < len, this isn't enough to determine that the CoW staging record is at least as large as the range passed into the helper. Fix both of them.

index f2addaf13c58..f8c51d8fbb3d 100644
@@ -581,8 +581,12 @@ xchk_xref_is_cow_staging(
 	if (rc.rc_domain != XFS_REFC_DOMAIN_COW)
 		xchk_btree_xref_set_corrupt(sc, sc->sa.refc_cur, 0);
 
+	/* Can't start after bno */
+	if (rc.rc_startblock > agbno)
+		xchk_btree_xref_set_corrupt(sc, sc->sa.refc_cur, 0);
+
 	/* Must be at least as long as what was passed in */
-	if (rc.rc_blockcount < len)
+	if (rc.rc_startblock + rc.rc_blockcount < agbno + len)
 		xchk_btree_xref_set_corrupt(sc, sc->sa.refc_cur, 0);
 }
 

index a024d50cf9d2..652d6b78b7a0 100644
@@ -609,8 +609,12 @@ xchk_xref_is_rt_cow_staging(
 	if (rc.rc_domain != XFS_REFC_DOMAIN_COW)
 		xchk_btree_xref_set_corrupt(sc, sc->sr.refc_cur, 0);
 
+	/* Can't start after bno */
+	if (rc.rc_startblock > bno)
+		xchk_btree_xref_set_corrupt(sc, sc->sr.refc_cur, 0);
+
 	/* Must be at least as long as what was passed in */
-	if (rc.rc_blockcount < len)
+	if (rc.rc_startblock + rc.rc_blockcount < bno + len)
 		xchk_btree_xref_set_corrupt(sc, sc->sr.refc_cur, 0);
 }
 

From: "Darrick J. Wong" <[email protected]>

[ Upstream commit 0d43368844a75ad13561a1198a3b027940730756 ]

LOLLM pointed out a bug in both of the refcount scrub predicates that determine if a range of blocks is marked as CoW staging in the btree. While it compares blockcount < len, this isn't enough to determine that the CoW staging record is at least as large as the range passed into the helper. Fix both of them.

---
 fs/xfs/scrub/refcount.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

index 304ea1e1bfb08..807785a2e2467 100644
@@ -569,8 +569,12 @@ xchk_xref_is_cow_staging(
 	if (rc.rc_domain != XFS_REFC_DOMAIN_COW)
 		xchk_btree_xref_set_corrupt(sc, sc->sa.refc_cur, 0);
 
+	/* Can't start after bno */
+	if (rc.rc_startblock > agbno)
+		xchk_btree_xref_set_corrupt(sc, sc->sa.refc_cur, 0);
+
 	/* Must be at least as long as what was passed in */
-	if (rc.rc_blockcount < len)
+	if (rc.rc_startblock + rc.rc_blockcount < agbno + len)
 		xchk_btree_xref_set_corrupt(sc, sc->sa.refc_cur, 0);
 }
 

2.53.0