NFS: Correct timing for assigning access cache timestamp

jira LE-1907
Rebuild_History Non-Buildable kernel-rt-5.14.0-284.30.1.rt14.315.el9_2
commit-author Chengen Du <chengen.du@canonical.com>
commit 21fd9e8

When the user's login time is newer than the cache's timestamp,
the original entry in the RB-tree will be replaced by a new entry.
Currently, the timestamp is only set if the entry is not found in
the RB-tree, which can cause the timestamp to be undefined when
the entry exists. This may result in a significant increase in
ACCESS operations if the timestamp is set to zero.

	Signed-off-by: Chengen Du <chengen.du@canonical.com>
Fixes: 0eb4381 ("NFS: Clear the file access cache upon login”)
	Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
	Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
(cherry picked from commit 21fd9e8)
	Signed-off-by: Jonathan Maple <jmaple@ciq.com>

Author: PlaidCat

fs/nfs/dir.c

@@ -3040,7 +3040,6 @@ static void nfs_access_add_rbtree(struct inode *inode,
 		else
 			goto found;
 	}
-	set->timestamp = ktime_get_ns();
 	rb_link_node(&set->rb_node, parent, p);
 	rb_insert_color(&set->rb_node, root_node);
 	list_add_tail(&set->lru, &nfsi->access_cache_entry_lru);
@@ -3065,6 +3064,7 @@ void nfs_access_add_cache(struct inode *inode, struct nfs_access_entry *set,
 	cache->fsgid = cred->fsgid;
 	cache->group_info = get_group_info(cred->group_info);
 	cache->mask = set->mask;
+	cache->timestamp = ktime_get_ns();
 
 	/* The above field assignments must be visible
 	 * before this item appears on the lru.  We cannot easily