[PATCH 3.16 046/136] cifs: Check uniqueid for SMB2+ and return -ESTALE if necessary

[Ben Hutchings]

3.16.80-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

commit a108471b5730b52017e73b58c9f486319d2ac308 upstream.

Commit 7196ac113a4f ("Fix to check Unique id and FileType when client
refer file directly.") checks whether the uniqueid of an inode has
changed when getting the inode info, but only when using the UNIX
extensions. Add a similar check for SMB2+, since this can be done
without an extra network roundtrip.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Signed-off-by: Steve French <smfrench@xxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/cifs/inode.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -815,8 +815,21 @@ cifs_get_inode_info(struct inode **inode
 			}
 		} else
 			fattr.cf_uniqueid = iunique(sb, ROOT_I);
-	} else
-		fattr.cf_uniqueid = CIFS_I(*inode)->uniqueid;
+	} else {
+		if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) &&
+		    validinum == false && server->ops->get_srv_inum) {
+			/*
+			 * Pass a NULL tcon to ensure we don't make a round
+			 * trip to the server. This only works for SMB2+.
+			 */
+			tmprc = server->ops->get_srv_inum(xid,
+				NULL, cifs_sb, full_path,
+				&fattr.cf_uniqueid, data);
+			if (tmprc)
+				fattr.cf_uniqueid = CIFS_I(*inode)->uniqueid;
+		} else
+			fattr.cf_uniqueid = CIFS_I(*inode)->uniqueid;
+	}
 
 	/* query for SFU type info if supported and needed */
 	if (fattr.cf_cifsattrs & ATTR_SYSTEM &&
@@ -857,6 +870,13 @@ cifs_get_inode_info(struct inode **inode
 	} else {
 		/* we already have inode, update it */
 
+		/* if uniqueid is different, return error */
+		if (unlikely(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM &&
+		    CIFS_I(*inode)->uniqueid != fattr.cf_uniqueid)) {
+			rc = -ESTALE;
+			goto cgii_exit;
+		}
+
 		/* if filetype is different, return error */
 		if (unlikely(((*inode)->i_mode & S_IFMT) !=
 		    (fattr.cf_mode & S_IFMT))) {