FAILED: patch "[PATCH] xfs: cap the block count of xfs_iomap_write_direct() at one extent" failed to apply to 5.10-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.10-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 <stable@vger.kernel.org>.

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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 66d1ce09ebd72709f8d739630c39f440445173fd
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109202734-failed-5.10-66d1ce09ebd7@kernel.org' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Thanks,
Sasha

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

From 66d1ce09ebd72709f8d739630c39f440445173fd Mon Sep 17 00:00:00 2001
From: Daejun Park <daejun7.park@samsung.com>
Date: Thu, 29 Oct 2026 11:23:02 +0900
Subject: [PATCH] xfs: cap the block count of xfs_iomap_write_direct() at one
 extent

xfs_iomap_write_direct() reserves blocks for the whole count in an
unsigned int. For a pNFS layout the client chooses that count, and an
RW LAYOUTGET for 16 TiB wraps the reservation and shuts XFS down.

xfs_bmapi_write() maps at most XFS_MAX_BMBT_EXTLEN blocks here, so cap
the count at that. nfsd asks again for the rest. The other callers get
the same mapping as before.

Suggested-by: Darrick J. Wong <djwong@kernel.org>
Suggested-by: Christoph Hellwig <hch@lst.de>
Suggested-by: Pankaj Raghav <p.raghav@samsung.com>
Fixes: 527851124d10 ("xfs: implement pNFS export operations")
Cc: stable@vger.kernel.org
Signed-off-by: Daejun Park <daejun7.park@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
---
 fs/xfs/xfs_iomap.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 99d48081c5ac3..c3465204b8d52 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -285,6 +285,14 @@ xfs_iomap_write_direct(
 
 	ASSERT(count_fsb > 0);
 
+	/*
+	 * xfs_bmapi_write() maps at most XFS_MAX_BMBT_EXTLEN blocks in one
+	 * mapping, so don't reserve blocks for more. A pNFS layout range
+	 * comes from a client, and its block count may not even fit the
+	 * 32-bit reservation. The caller maps the rest with a later call.
+	 */
+	count_fsb = min_t(xfs_filblks_t, count_fsb, XFS_MAX_BMBT_EXTLEN);
+
 	resaligned = xfs_aligned_fsb_count(offset_fsb, count_fsb,
 					   xfs_get_extsz_hint(ip));
 	if (unlikely(XFS_IS_REALTIME_INODE(ip))) {
-- 
2.53.0