6 files changed, 40 insertions, 14 deletions

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 266d2059b9b8..dfbcd1b00b0a 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -365,8 +365,8 @@ must be done in the RCU callback.
 [recommended]
         vfs now tries to do path walking in "rcu-walk mode", which avoids
 atomic operations and scalability hazards on dentries and inodes (see
-Documentation/filesystems/path-walk.txt). d_hash and d_compare changes (above)
-are examples of the changes required to support this. For more complex
+Documentation/filesystems/path-lookup.txt). d_hash and d_compare changes
+(above) are examples of the changes required to support this. For more complex
 filesystem callbacks, the vfs drops out of rcu-walk mode before the fs call, so
 no changes are required to the filesystem. However, this is costly and loses
 the benefits of rcu-walk mode. We will begin to add filesystem callbacks that
@@ -383,8 +383,8 @@ Documentation/filesystems/vfs.txt for more details.
 
         permission and check_acl are inode permission checks that are called
 on many or all directory inodes on the way down a path walk (to check for
-exec permission). These must now be rcu-walk aware (flags & IPERM_RCU). See
-Documentation/filesystems/vfs.txt for more details.
+exec permission). These must now be rcu-walk aware (flags & IPERM_FLAG_RCU).
+See Documentation/filesystems/vfs.txt for more details.
  
 --
 [mandatory]
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index fbb324e2bd43..cae6d27c9f5b 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -415,8 +415,8 @@ otherwise noted.
   permission: called by the VFS to check for access rights on a POSIX-like
         filesystem.
 
-        May be called in rcu-walk mode (flags & IPERM_RCU). If in rcu-walk
-        mode, the filesystem must check the permission without blocking or
+        May be called in rcu-walk mode (flags & IPERM_FLAG_RCU). If in rcu-walk
+        mode, the filesystem must check the permission without blocking or
         storing to the inode.
 
         If a situation is encountered that rcu-walk cannot handle, return
diff --git a/fs/namei.c b/fs/namei.c
index 0b14f6910fc6..86643302079e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -479,6 +479,14 @@ static int nameidata_dentry_drop_rcu(struct nameidata *nd, struct dentry *dentry
         struct fs_struct *fs = current->fs;
         struct dentry *parent = nd->path.dentry;
 
+        /*
+         * It can be possible to revalidate the dentry that we started
+         * the path walk with. force_reval_path may also revalidate the
+         * dentry already committed to the nameidata.
+         */
+        if (unlikely(parent == dentry))
+                return nameidata_drop_rcu(nd);
+
         BUG_ON(!(nd->flags & LOOKUP_RCU));
         if (nd->root.mnt) {
                 spin_lock(&fs->lock);
@@ -583,6 +591,13 @@ void release_open_intent(struct nameidata *nd)
                 fput(nd->intent.open.file);
 }
 
+/*
+ * Call d_revalidate and handle filesystems that request rcu-walk
+ * to be dropped. This may be called and return in rcu-walk mode,
+ * regardless of success or error. If -ECHILD is returned, the caller
+ * must return -ECHILD back up the path walk stack so path walk may
+ * be restarted in ref-walk mode.
+ */
 static int d_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
         int status;
@@ -673,6 +688,9 @@ force_reval_path(struct path *path, struct nameidata *nd)
                 return 0;
 
         if (!status) {
+                /* Don't d_invalidate in rcu-walk mode */
+                if (nameidata_drop_rcu(nd))
+                        return -ECHILD;
                 d_invalidate(dentry);
                 status = -ESTALE;
         }
@@ -2105,11 +2123,13 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
                 dir = nd->path.dentry;
         case LAST_DOT:
                 if (need_reval_dot(dir)) {
-                        error = d_revalidate(nd->path.dentry, nd);
-                        if (!error)
-                                error = -ESTALE;
-                        if (error < 0)
+                        int status = d_revalidate(nd->path.dentry, nd);
+                        if (!status)
+                                status = -ESTALE;
+                        if (status < 0) {
+                                error = status;
                                 goto exit;
+                        }
                 }
                 /* fallthrough */
         case LAST_ROOT:
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 64ee240f3c80..df8c03a02161 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1406,11 +1406,15 @@ no_open:
 static int nfs_open_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
         struct dentry *parent = NULL;
-        struct inode *inode = dentry->d_inode;
+        struct inode *inode;
         struct inode *dir;
         struct nfs_open_context *ctx;
         int openflags, ret = 0;
 
+        if (nd->flags & LOOKUP_RCU)
+                return -ECHILD;
+
+        inode = dentry->d_inode;
         if (!is_atomic_open(nd) || d_mountpoint(dentry))
                 goto no_open;
 
diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h
index 9ee97e7f2be4..b2adbb4b2f73 100644
--- a/include/linux/list_bl.h
+++ b/include/linux/list_bl.h
@@ -16,7 +16,7 @@
  * some fast and compact auxiliary data.
  */
 
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
+#if defined(CONFIG_SMP)
 #define LIST_BL_LOCKMASK        1UL
 #else
 #define LIST_BL_LOCKMASK        0UL
@@ -62,7 +62,8 @@ static inline void hlist_bl_set_first(struct hlist_bl_head *h,
                                         struct hlist_bl_node *n)
 {
         LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
-        LIST_BL_BUG_ON(!((unsigned long)h->first & LIST_BL_LOCKMASK));
+        LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
+                                                        LIST_BL_LOCKMASK);
         h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK);
 }
 
diff --git a/include/linux/rculist_bl.h b/include/linux/rculist_bl.h
index b872b493724d..cf1244fbf3b6 100644
--- a/include/linux/rculist_bl.h
+++ b/include/linux/rculist_bl.h
@@ -11,7 +11,8 @@ static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
                                         struct hlist_bl_node *n)
 {
         LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
-        LIST_BL_BUG_ON(!((unsigned long)h->first & LIST_BL_LOCKMASK));
+        LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
+                                                        LIST_BL_LOCKMASK);
         rcu_assign_pointer(h->first,
                 (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
 }