cifs: use CreationTime like an i_generation field

Reduce false inode collisions by using the CreationTime like an
i_generation field. This way, even if the server ends up reusing
a uniqueid after a delete/create cycle, we can avoid matching
the inode incorrectly.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index a853a89..0c7e369 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -518,6 +518,7 @@
 
 	fattr->cf_eof = le64_to_cpu(info->EndOfFile);
 	fattr->cf_bytes = le64_to_cpu(info->AllocationSize);
+	fattr->cf_createtime = le64_to_cpu(info->CreationTime);
 
 	if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
 		fattr->cf_mode = S_IFDIR | cifs_sb->mnt_dir_mode;
@@ -779,6 +780,10 @@
 	if (CIFS_I(inode)->uniqueid != fattr->cf_uniqueid)
 		return 0;
 
+	/* use createtime like an i_generation field */
+	if (CIFS_I(inode)->createtime != fattr->cf_createtime)
+		return 0;
+
 	/* don't match inode of different type */
 	if ((inode->i_mode & S_IFMT) != (fattr->cf_mode & S_IFMT))
 		return 0;
@@ -796,6 +801,7 @@
 	struct cifs_fattr *fattr = (struct cifs_fattr *) opaque;
 
 	CIFS_I(inode)->uniqueid = fattr->cf_uniqueid;
+	CIFS_I(inode)->createtime = fattr->cf_createtime;
 	return 0;
 }