linux-kernel - [PATCH] cifs: Fix missing set of remote_i

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Date: Fri, 24 May 2024 15:23:36 +0100
From: David Howells <dhowells@...hat.com>
To: Steve French <sfrench@...ba.org>
cc: dhowells@...hat.com, Paulo Alcantara <pc@...guebit.com>,
    Shyam Prasad N <nspmangalore@...il.com>,
    Rohith Surabattula <rohiths.msft@...il.com>,
    Jeff Layton <jlayton@...nel.org>, linux-cifs@...r.kernel.org,
    netfs@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
    linux-kernel@...r.kernel.org
Subject: [PATCH] cifs: Fix missing set of remote_i_size

Occasionally, the generic/001 xfstest will fail indicating corruption in
one of the copy chains when run on cifs against a server that supports
FSCTL_DUPLICATE_EXTENTS_TO_FILE (eg. Samba with a share on btrfs).  The
problem is that the remote_i_size value isn't updated by cifs_setsize()
when called by smb2_duplicate_extents(), but i_size *is*.

This may cause cifs_remap_file_range() to then skip the bit after calling
->duplicate_extents() that sets sizes.

Fix this by calling netfs_resize_file() in smb2_duplicate_extents() before
calling cifs_setsize() to set i_size.

This means we don't then need to call netfs_resize_file() upon return from
->duplicate_extents(), but we also fix the test to compare against the pre-dup
inode size.

[Note that this goes back before the addition of remote_i_size with the
netfs_inode struct.  It should probably have been setting cifsi->server_eof
previously.]

Fixes: cfc63fc8126a ("smb3: fix cached file size problems in duplicate extents (reflink)")
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Steve French <sfrench@...ba.org>
cc: Paulo Alcantara <pc@...guebit.com>
cc: Shyam Prasad N <nspmangalore@...il.com>
cc: Rohith Surabattula <rohiths.msft@...il.com>
cc: Jeff Layton <jlayton@...nel.org>
cc: linux-cifs@...r.kernel.org
cc: netfs@...ts.linux.dev
---
 fs/smb/client/cifsfs.c  |    6 +++---
 fs/smb/client/smb2ops.c |    1 +
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index 14810ffd15c8..bb86fc0641d8 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -1227,7 +1227,7 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	struct cifsFileInfo *smb_file_src = src_file->private_data;
 	struct cifsFileInfo *smb_file_target = dst_file->private_data;
 	struct cifs_tcon *target_tcon, *src_tcon;
-	unsigned long long destend, fstart, fend, new_size;
+	unsigned long long destend, fstart, fend, old_size, new_size;
 	unsigned int xid;
 	int rc;
 
@@ -1294,6 +1294,7 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 		goto unlock;
 	if (fend > target_cifsi->netfs.zero_point)
 		target_cifsi->netfs.zero_point = fend + 1;
+	old_size = target_cifsi->netfs.remote_i_size;
 
 	/* Discard all the folios that overlap the destination region. */
 	cifs_dbg(FYI, "about to discard pages %llx-%llx\n", fstart, fend);
@@ -1306,9 +1307,8 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	if (target_tcon->ses->server->ops->duplicate_extents) {
 		rc = target_tcon->ses->server->ops->duplicate_extents(xid,
 			smb_file_src, smb_file_target, off, len, destoff);
-		if (rc == 0 && new_size > i_size_read(target_inode)) {
+		if (rc == 0 && new_size > old_size) {
 			truncate_setsize(target_inode, new_size);
-			netfs_resize_file(&target_cifsi->netfs, new_size, true);
 			fscache_resize_cookie(cifs_inode_cookie(target_inode),
 					      new_size);
 		}
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index b87b70edd0be..4ce6c3121a7e 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -2028,6 +2028,7 @@ smb2_duplicate_extents(const unsigned int xid,
 		 * size will be queried on next revalidate, but it is important
 		 * to make sure that file's cached size is updated immediately
 		 */
+		netfs_resize_file(netfs_inode(inode), dest_off + len, true);
 		cifs_setsize(inode, dest_off + len);
 	}
 	rc = SMB2_ioctl(xid, tcon, trgtfile->fid.persistent_fid,