Patch "smb: client: refresh referral without acquiring refpath_lock" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    smb: client: refresh referral without acquiring refpath_lock

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     smb-client-refresh-referral-without-acquiring-refpat.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit bb3d804a61cae527f7dcf796c0db547fe7b8a3a3
Author: Paulo Alcantara <pc@xxxxxxxxxxxxx>
Date:   Mon Apr 1 22:44:07 2024 -0300

    smb: client: refresh referral without acquiring refpath_lock
    
    [ Upstream commit 0a05ad21d77a188d06481c36d6016805a881bcc0 ]
    
    Avoid refreshing DFS referral with refpath_lock acquired as the I/O
    could block for a while due to a potentially disconnected or slow DFS
    root server and then making other threads - that use same @server and
    don't require a DFS root server - unable to make any progress.
    
    Cc: stable@xxxxxxxxxxxxxxx # 6.4+
    Signed-off-by: Paulo Alcantara (Red Hat) <pc@xxxxxxxxxxxxx>
    Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/smb/client/dfs_cache.c b/fs/smb/client/dfs_cache.c
index 0552a864ff08f..11c8efecf7aa1 100644
--- a/fs/smb/client/dfs_cache.c
+++ b/fs/smb/client/dfs_cache.c
@@ -1172,8 +1172,8 @@ static bool is_ses_good(struct cifs_ses *ses)
 	return ret;
 }
 
-/* Refresh dfs referral of tcon and mark it for reconnect if needed */
-static int __refresh_tcon(const char *path, struct cifs_ses *ses, bool force_refresh)
+/* Refresh dfs referral of @ses and mark it for reconnect if needed */
+static void __refresh_ses_referral(struct cifs_ses *ses, bool force_refresh)
 {
 	struct TCP_Server_Info *server = ses->server;
 	DFS_CACHE_TGT_LIST(old_tl);
@@ -1181,10 +1181,21 @@ static int __refresh_tcon(const char *path, struct cifs_ses *ses, bool force_ref
 	bool needs_refresh = false;
 	struct cache_entry *ce;
 	unsigned int xid;
+	char *path = NULL;
 	int rc = 0;
 
 	xid = get_xid();
 
+	mutex_lock(&server->refpath_lock);
+	if (server->leaf_fullpath) {
+		path = kstrdup(server->leaf_fullpath + 1, GFP_ATOMIC);
+		if (!path)
+			rc = -ENOMEM;
+	}
+	mutex_unlock(&server->refpath_lock);
+	if (!path)
+		goto out;
+
 	down_read(&htable_rw_lock);
 	ce = lookup_cache_entry(path);
 	needs_refresh = force_refresh || IS_ERR(ce) || cache_entry_expired(ce);
@@ -1218,19 +1229,17 @@ static int __refresh_tcon(const char *path, struct cifs_ses *ses, bool force_ref
 	free_xid(xid);
 	dfs_cache_free_tgts(&old_tl);
 	dfs_cache_free_tgts(&new_tl);
-	return rc;
+	kfree(path);
 }
 
-static int refresh_tcon(struct cifs_tcon *tcon, bool force_refresh)
+static inline void refresh_ses_referral(struct cifs_ses *ses)
 {
-	struct TCP_Server_Info *server = tcon->ses->server;
-	struct cifs_ses *ses = tcon->ses;
+	__refresh_ses_referral(ses, false);
+}
 
-	mutex_lock(&server->refpath_lock);
-	if (server->leaf_fullpath)
-		__refresh_tcon(server->leaf_fullpath + 1, ses, force_refresh);
-	mutex_unlock(&server->refpath_lock);
-	return 0;
+static inline void force_refresh_ses_referral(struct cifs_ses *ses)
+{
+	__refresh_ses_referral(ses, true);
 }
 
 /**
@@ -1271,25 +1280,20 @@ int dfs_cache_remount_fs(struct cifs_sb_info *cifs_sb)
 	 */
 	cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
 
-	return refresh_tcon(tcon, true);
+	force_refresh_ses_referral(tcon->ses);
+	return 0;
 }
 
 /* Refresh all DFS referrals related to DFS tcon */
 void dfs_cache_refresh(struct work_struct *work)
 {
-	struct TCP_Server_Info *server;
 	struct cifs_tcon *tcon;
 	struct cifs_ses *ses;
 
 	tcon = container_of(work, struct cifs_tcon, dfs_cache_work.work);
 
-	for (ses = tcon->ses; ses; ses = ses->dfs_root_ses) {
-		server = ses->server;
-		mutex_lock(&server->refpath_lock);
-		if (server->leaf_fullpath)
-			__refresh_tcon(server->leaf_fullpath + 1, ses, false);
-		mutex_unlock(&server->refpath_lock);
-	}
+	for (ses = tcon->ses; ses; ses = ses->dfs_root_ses)
+		refresh_ses_referral(ses);
 
 	queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
 			   atomic_read(&dfs_cache_ttl) * HZ);