Merge branch 'vfs-scale-working' of git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin

* 'vfs-scale-working' of git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin:
fs: fix do_last error case when need_reval_dot
nfs: add missing rcu-walk check
fs: hlist UP debug fixup
fs: fix dropping of rcu-walk from force_reval_path
fs: force_reval_path drop rcu-walk before d_invalidate
fs: small rcu-walk documentation fixes

Fixed up trivial conflicts in Documentation/filesystems/porting

Documentation/filesystems/porting

···
 [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
···
 
 	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]

Documentation/filesystems/vfs.txt

···
   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

fs/namei.c

···
 	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);
···
 		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;
···
 		return 0;
 
 	if (!status) {
+		/* Don't d_invalidate in rcu-walk mode */
+		if (nameidata_drop_rcu(nd))
+			return -ECHILD;
 		d_invalidate(dentry);
 		status = -ESTALE;
 	}
···
 		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:

fs/nfs/dir.c

···
 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;
 

include/linux/list_bl.h

···
  * 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
···
 					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);
 }
 

include/linux/rculist_bl.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));
 }