smb: client: fix missing timestamp updates after utime(2)

Don't reuse open handle when changing timestamps to prevent the server
from disabling automatic timestamp updates as per MS-FSA 2.1.4.17.

---8<---
import os
import time

filename = '/mnt/foo'

def print_stat(prefix):
    st = os.stat(filename)
    print(prefix, ': ', time.ctime(st.st_atime), time.ctime(st.st_ctime))

fd = os.open(filename, os.O_CREAT|os.O_TRUNC|os.O_WRONLY, 0o644)
print_stat('old')
os.utime(fd, None)
time.sleep(2)
os.write(fd, b'foo')
os.close(fd)
time.sleep(2)
print_stat('new')
---8<---

Before patch:

$ mount.cifs //srv/share /mnt -o ...
$ python3 run.py
old :  Fri Oct  3 14:01:21 2025 Fri Oct  3 14:01:21 2025
new :  Fri Oct  3 14:01:21 2025 Fri Oct  3 14:01:21 2025

After patch:

$ mount.cifs //srv/share /mnt -o ...
$ python3 run.py
old :  Fri Oct  3 17:03:34 2025 Fri Oct  3 17:03:34 2025
new :  Fri Oct  3 17:03:36 2025 Fri Oct  3 17:03:36 2025

Fixes: b6f2a0f89d7e ("cifs: for compound requests, use open handle if possible")
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Cc: Frank Sorenson <sorenson@redhat.com>
Reviewed-by: David Howells <dhowells@redhat.com>
Cc: linux-cifs@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
index 0985db9f86e5104b44cf55aa4dd5833e45251e25..e441fa2e768979feae86b308fbda49f10ca64a97 100644 (file)
--- a/fs/smb/client/smb2inode.c
+++ b/fs/smb/client/smb2inode.c
@@ -1382,31 +1382,33 @@ int
 smb2_set_file_info(struct inode *inode, const char *full_path,
                   FILE_BASIC_INFO *buf, const unsigned int xid)
 {
-       struct cifs_open_parms oparms;
+       struct kvec in_iov = { .iov_base = buf, .iov_len = sizeof(*buf), };
        struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
+       struct cifsFileInfo *cfile = NULL;
+       struct cifs_open_parms oparms;
        struct tcon_link *tlink;
        struct cifs_tcon *tcon;
-       struct cifsFileInfo *cfile;
-       struct kvec in_iov = { .iov_base = buf, .iov_len = sizeof(*buf), };
-       int rc;
-
-       if ((buf->CreationTime == 0) && (buf->LastAccessTime == 0) &&
-           (buf->LastWriteTime == 0) && (buf->ChangeTime == 0) &&
-           (buf->Attributes == 0))
-               return 0; /* would be a no op, no sense sending this */
+       int rc = 0;
 
        tlink = cifs_sb_tlink(cifs_sb);
        if (IS_ERR(tlink))
                return PTR_ERR(tlink);
        tcon = tlink_tcon(tlink);
 
-       cifs_get_writable_path(tcon, full_path, FIND_WR_ANY, &cfile);
+       if ((buf->CreationTime == 0) && (buf->LastAccessTime == 0) &&
+           (buf->LastWriteTime == 0) && (buf->ChangeTime == 0)) {
+               if (buf->Attributes == 0)
+                       goto out; /* would be a no op, no sense sending this */
+               cifs_get_writable_path(tcon, full_path, FIND_WR_ANY, &cfile);
+       }
+
        oparms = CIFS_OPARMS(cifs_sb, tcon, full_path, FILE_WRITE_ATTRIBUTES,
                             FILE_OPEN, 0, ACL_NO_MODE);
        rc = smb2_compound_op(xid, tcon, cifs_sb,
                              full_path, &oparms, &in_iov,
                              &(int){SMB2_OP_SET_INFO}, 1,
                              cfile, NULL, NULL, NULL);
+out:
        cifs_put_tlink(tlink);
        return rc;
 }