[PATCH 6.6 005/158] smb: client: refresh referral without acquiring refpath_lock

Greg Kroah-Hartman
2024-04-23T21:42:49Z

From: Paulo Alcantara <pc@manguebit.com>

[ 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@vger.kernel.org # 6.4+
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/smb/client/dfs_cache.c | 44 +++++++++++++++++++++------------------
1 file changed, 24 insertions(+), 20 deletions(-)

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);
--
2.43.0