FAILED: patch "[PATCH] smb: client: require stable pages for SMB compression" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 8667061cf99394526dd9c0ea2662e6bbc7ae7848
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026110441-ethically-speech-8e44@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From 8667061cf99394526dd9c0ea2662e6bbc7ae7848 Mon Sep 17 00:00:00 2001
From: Paulo Alcantara <[email protected]>
Date: Tue, 13 Oct 2026 10:33:41 -0300
Subject: [PATCH] smb: client: require stable pages for SMB compression

Like signing, SMB compression builds the write payload from the pagecache
folios: should_compress() lets a write request through and smb_compress() compresses those folios on the way to the socket. If a buffered write mutates a folio while a write subrequest is still in flight, the compressed bytes no longer correspond to a consistent view of the data, and the server silently stores corrupted contents - worse than the signed case, which at least fails loudly with STATUS_ACCESS_DENIED.

Mark the mapping for stable writes when a write may be compressed, i.e. the same condition should_compress() tests (compression negotiated and the share allows compressed data), so netfs_perform_write() waits for writeback to complete before modifying an in-flight folio.

index 43a2d7982488..d94007deb548 100644
@@ -88,7 +88,9 @@ static void cifs_set_ops(struct inode *inode)
 		else
 			inode->i_data.a_ops = &cifs_addr_ops;
 		mapping_set_large_folios(inode->i_mapping);
-		if (tcon->ses->server->sign)
+		if (tcon->ses->server->sign ||
+		    (tcon->ses->server->compression.enabled &&
+		     (tcon->share_flags & SMB2_SHAREFLAG_COMPRESS_DATA)))
 			mapping_set_stable_writes(inode->i_mapping);
 		break;
 	case S_IFDIR:

From: Paulo Alcantara <[email protected]>

[ Upstream commit 8667061cf99394526dd9c0ea2662e6bbc7ae7848 ]

Like signing, SMB compression builds the write payload from the pagecache
folios: should_compress() lets a write request through and smb_compress() compresses those folios on the way to the socket. If a buffered write mutates a folio while a write subrequest is still in flight, the compressed bytes no longer correspond to a consistent view of the data, and the server silently stores corrupted contents - worse than the signed case, which at least fails loudly with STATUS_ACCESS_DENIED.

Mark the mapping for stable writes when a write may be compressed, i.e. the same condition should_compress() tests (compression negotiated and the share allows compressed data), so netfs_perform_write() waits for writeback to complete before modifying an in-flight folio.

---
 fs/smb/client/inode.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

index 7c638b8d5490f..c63c74dd9d434 100644
@@ -87,7 +87,9 @@ static void cifs_set_ops(struct inode *inode)
 		else
 			inode->i_data.a_ops = &cifs_addr_ops;
 		mapping_set_large_folios(inode->i_mapping);
-		if (cifs_sb_master_tcon(cifs_sb)->ses->server->sign)
+		if (cifs_sb_master_tcon(cifs_sb)->ses->server->sign ||
+		    (cifs_sb_master_tcon(cifs_sb)->ses->server->compression.enabled &&
+		     (cifs_sb_master_tcon(cifs_sb)->share_flags & SMB2_SHAREFLAG_COMPRESS_DATA)))
 			mapping_set_stable_writes(inode->i_mapping);
 		break;
 	case S_IFDIR:

2.53.0