FAILED: patch "[PATCH] smb: client: discard post-EOF pagecache when extending a file" 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 da4fe97fb6c730d9c94a115c7bfa6f98e0d578d0
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026100529-sludge-wasting-0d0a@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From da4fe97fb6c730d9c94a115c7bfa6f98e0d578d0 Mon Sep 17 00:00:00 2001
From: Paulo Alcantara <[email protected]>
Date: Sun, 20 Sep 2026 16:09:30 -0300
Subject: [PATCH] smb: client: discard post-EOF pagecache when extending a file
via zero range

smb3_zero_range() removed the pagecache only for the range being zeroed, so when it extends the file the folio straddling the old EOF - which may hold data dirtied past EOF through an mmap - was never dropped and became visible as file content once the file was extended.

Lower the discard boundary to the smaller of the zero-range offset and the old EOF.

index 1ada1c0a728d..849cfd2de705 100644
@@ -3560,8 +3560,11 @@ static long smb3_zero_range(struct file *file, struct cifs_tcon *tcon,
 	/*
 	 * We zero the range through ioctl, so we need remove the page caches
 	 * first, otherwise the data may be inconsistent with the server.
+	 *
+	 * Start at the old EOF when extending so the folio straddling it, which
+	 * may hold data written past EOF through an mmap, is dropped too.
 	 */
-	truncate_pagecache_range(inode, offset, offset + len - 1);
+	truncate_pagecache_range(inode, min(offset, i_size), offset + len - 1);
 	netfs_wait_for_outstanding_io(inode);
 
 	/* if file not oplocked can't be sure whether asking to extend size */

From: Paulo Alcantara <[email protected]>

[ Upstream commit da4fe97fb6c730d9c94a115c7bfa6f98e0d578d0 ]

smb3_zero_range() removed the pagecache only for the range being zeroed, so when it extends the file the folio straddling the old EOF - which may hold data dirtied past EOF through an mmap - was never dropped and became visible as file content once the file was extended.

Lower the discard boundary to the smaller of the zero-range offset and the old EOF.

---
 fs/smb/client/smb2ops.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

index 887ffa77aa183..a82abe2e8ce14 100644
@@ -3283,8 +3283,11 @@ static long smb3_zero_range(struct file *file, struct cifs_tcon *tcon,
 	/*
 	 * We zero the range through ioctl, so we need remove the page caches
 	 * first, otherwise the data may be inconsistent with the server.
+	 *
+	 * Start at the old EOF when extending so the folio straddling it, which
+	 * may hold data written past EOF through an mmap, is dropped too.
 	 */
-	truncate_pagecache_range(inode, offset, offset + len - 1);
+	truncate_pagecache_range(inode, min(offset, i_size), offset + len - 1);
 
 	/* if file not oplocked can't be sure whether asking to extend size */
 	rc = -EOPNOTSUPP;

2.53.0