queue-6.8/smb-client-refresh-referral-without-acquiring-refpath_lock.patch

   1 From 0a05ad21d77a188d06481c36d6016805a881bcc0 Mon Sep 17 00:00:00 2001
   2 From: Paulo Alcantara <pc@manguebit.com>
   3 Date: Mon, 1 Apr 2024 22:44:07 -0300
   4 Subject: smb: client: refresh referral without acquiring refpath_lock
   5
   6 From: Paulo Alcantara <pc@manguebit.com>
   7
   8 commit 0a05ad21d77a188d06481c36d6016805a881bcc0 upstream.
   9
  10 Avoid refreshing DFS referral with refpath_lock acquired as the I/O
  11 could block for a while due to a potentially disconnected or slow DFS
  12 root server and then making other threads - that use same @server and
  13 don't require a DFS root server - unable to make any progress.
  14
  15 Cc: stable@vger.kernel.org # 6.4+
  16 Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
  17 Signed-off-by: Steve French <stfrench@microsoft.com>
  18 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  19 ---
  20  fs/smb/client/dfs_cache.c |   44 ++++++++++++++++++++++++--------------------
  21  1 file changed, 24 insertions(+), 20 deletions(-)
  22
  23 --- a/fs/smb/client/dfs_cache.c
  24 +++ b/fs/smb/client/dfs_cache.c
  25 @@ -1172,8 +1172,8 @@ static bool is_ses_good(struct cifs_ses
  26         return ret;
  27  }
  28
  29 -/* Refresh dfs referral of tcon and mark it for reconnect if needed */
  30 -static int __refresh_tcon(const char *path, struct cifs_ses *ses, bool force_refresh)
  31 +/* Refresh dfs referral of @ses and mark it for reconnect if needed */
  32 +static void __refresh_ses_referral(struct cifs_ses *ses, bool force_refresh)
  33  {
  34         struct TCP_Server_Info *server = ses->server;
  35         DFS_CACHE_TGT_LIST(old_tl);
  36 @@ -1181,10 +1181,21 @@ static int __refresh_tcon(const char *pa
  37         bool needs_refresh = false;
  38         struct cache_entry *ce;
  39         unsigned int xid;
  40 +       char *path = NULL;
  41         int rc = 0;
  42
  43         xid = get_xid();
  44
  45 +       mutex_lock(&server->refpath_lock);
  46 +       if (server->leaf_fullpath) {
  47 +               path = kstrdup(server->leaf_fullpath + 1, GFP_ATOMIC);
  48 +               if (!path)
  49 +                       rc = -ENOMEM;
  50 +       }
  51 +       mutex_unlock(&server->refpath_lock);
  52 +       if (!path)
  53 +               goto out;
  54 +
  55         down_read(&htable_rw_lock);
  56         ce = lookup_cache_entry(path);
  57         needs_refresh = force_refresh || IS_ERR(ce) || cache_entry_expired(ce);
  58 @@ -1218,19 +1229,17 @@ out:
  59         free_xid(xid);
  60         dfs_cache_free_tgts(&old_tl);
  61         dfs_cache_free_tgts(&new_tl);
  62 -       return rc;
  63 +       kfree(path);
  64  }
  65
  66 -static int refresh_tcon(struct cifs_tcon *tcon, bool force_refresh)
  67 +static inline void refresh_ses_referral(struct cifs_ses *ses)
  68  {
  69 -       struct TCP_Server_Info *server = tcon->ses->server;
  70 -       struct cifs_ses *ses = tcon->ses;
  71 +       __refresh_ses_referral(ses, false);
  72 +}
  73
  74 -       mutex_lock(&server->refpath_lock);
  75 -       if (server->leaf_fullpath)
  76 -               __refresh_tcon(server->leaf_fullpath + 1, ses, force_refresh);
  77 -       mutex_unlock(&server->refpath_lock);
  78 -       return 0;
  79 +static inline void force_refresh_ses_referral(struct cifs_ses *ses)
  80 +{
  81 +       __refresh_ses_referral(ses, true);
  82  }
  83
  84  /**
  85 @@ -1271,25 +1280,20 @@ int dfs_cache_remount_fs(struct cifs_sb_
  86          */
  87         cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
  88
  89 -       return refresh_tcon(tcon, true);
  90 +       force_refresh_ses_referral(tcon->ses);
  91 +       return 0;
  92  }
  93
  94  /* Refresh all DFS referrals related to DFS tcon */
  95  void dfs_cache_refresh(struct work_struct *work)
  96  {
  97 -       struct TCP_Server_Info *server;
  98         struct cifs_tcon *tcon;
  99         struct cifs_ses *ses;
 100
 101         tcon = container_of(work, struct cifs_tcon, dfs_cache_work.work);
 102
 103 -       for (ses = tcon->ses; ses; ses = ses->dfs_root_ses) {
 104 -               server = ses->server;
 105 -               mutex_lock(&server->refpath_lock);
 106 -               if (server->leaf_fullpath)
 107 -                       __refresh_tcon(server->leaf_fullpath + 1, ses, false);
 108 -               mutex_unlock(&server->refpath_lock);
 109 -       }
 110 +       for (ses = tcon->ses; ses; ses = ses->dfs_root_ses)
 111 +               refresh_ses_referral(ses);
 112
 113         queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
 114                            atomic_read(&dfs_cache_ttl) * HZ);