cifs: rcu-delay unload_nls() and freeing sbi

makes ->d_hash(), ->d_compare() and ->permission() safety in RCU mode
independent from vfsmount_lock.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 9 insertions, 2 deletions

diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index 37e4a72a7d1c..9409fa10bd5c 100644
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -65,5 +65,6 @@ struct cifs_sb_info {
         char   *mountdata; /* options received at mount time or via DFS refs */
         struct backing_dev_info bdi;
         struct delayed_work prune_tlinks;
+        struct rcu_head rcu;
 };
 #endif                          /* _CIFS_FS_SB_H */
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index a279ffc0bc29..886db8b41e35 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3755,6 +3755,13 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
         return rc;
 }
 
+static void delayed_free(struct rcu_head *p)
+{
+        struct cifs_sb_info *sbi = container_of(p, struct cifs_sb_info, rcu);
+        unload_nls(sbi->local_nls);
+        kfree(sbi);
+}
+
 void
 cifs_umount(struct cifs_sb_info *cifs_sb)
 {
@@ -3779,8 +3786,7 @@ cifs_umount(struct cifs_sb_info *cifs_sb)
 
         bdi_destroy(&cifs_sb->bdi);
         kfree(cifs_sb->mountdata);
-        unload_nls(cifs_sb->local_nls);
-        kfree(cifs_sb);
+        call_rcu(&cifs_sb->rcu, delayed_free);
 }
 
 int