NFS: Judge the file access cache's timestamp in rcu path

jira LE-1907
Rebuild_History Non-Buildable kernel-rt-5.14.0-284.30.1.rt14.315.el9_2
commit-author Chengen Du <[email protected]>
commit 029085b

If the user's login time is newer than the cache's timestamp,
we expect the cache may be stale and need to clear.
The stale cache will remain in the list's tail if no other
users operate on that inode.
Once the user accesses the inode, the stale cache will be
returned in rcu path.

	Signed-off-by: Chengen Du <[email protected]>
	Signed-off-by: Trond Myklebust <[email protected]>
(cherry picked from commit 029085b)
	Signed-off-by: Jonathan Maple <[email protected]>

Author: PlaidCat

fs/nfs/dir.c

@@ -2976,6 +2976,7 @@ static int nfs_access_get_cached_rcu(struct inode *inode, const struct cred *cre
 	 * but do it without locking.
 	 */
 	struct nfs_inode *nfsi = NFS_I(inode);
+	u64 login_time = nfs_access_login_time(current, cred);
 	struct nfs_access_entry *cache;
 	int err = -ECHILD;
 	struct list_head *lh;
@@ -2990,6 +2991,8 @@ static int nfs_access_get_cached_rcu(struct inode *inode, const struct cred *cre
 		cache = NULL;
 	if (cache == NULL)
 		goto out;
+	if ((s64)(login_time - cache->timestamp) > 0)
+		goto out;
 	if (nfs_check_cache_invalid(inode, NFS_INO_INVALID_ACCESS))
 		goto out;
 	*mask = cache->mask;