1 files changed, 66 insertions, 10 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 3d607bd80e09..4a98bf154d88 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -308,6 +308,26 @@ int generic_permission(struct inode *inode, int mask)
         return -EACCES;
 }
 
+/*
+ * We _really_ want to just do "generic_permission()" without
+ * even looking at the inode->i_op values. So we keep a cache
+ * flag in inode->i_opflags, that says "this has not special
+ * permission function, use the fast case".
+ */
+static inline int do_inode_permission(struct inode *inode, int mask)
+{
+        if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
+                if (likely(inode->i_op->permission))
+                        return inode->i_op->permission(inode, mask);
+
+                /* This gets set once for the inode lifetime */
+                spin_lock(&inode->i_lock);
+                inode->i_opflags |= IOP_FASTPERM;
+                spin_unlock(&inode->i_lock);
+        }
+        return generic_permission(inode, mask);
+}
+
 /**
  * inode_permission  -  check for access rights to a given inode
  * @inode:      inode to check permission on
@@ -322,7 +342,7 @@ int inode_permission(struct inode *inode, int mask)
 {
         int retval;
 
-        if (mask & MAY_WRITE) {
+        if (unlikely(mask & MAY_WRITE)) {
                 umode_t mode = inode->i_mode;
 
                 /*
@@ -339,11 +359,7 @@ int inode_permission(struct inode *inode, int mask)
                         return -EACCES;
         }
 
-        if (inode->i_op->permission)
-                retval = inode->i_op->permission(inode, mask);
-        else
-                retval = generic_permission(inode, mask);
-
+        retval = do_inode_permission(inode, mask);
         if (retval)
                 return retval;
 
@@ -1245,6 +1261,26 @@ static void terminate_walk(struct nameidata *nd)
         }
 }
 
+/*
+ * Do we need to follow links? We _really_ want to be able
+ * to do this check without having to look at inode->i_op,
+ * so we keep a cache of "no, this doesn't need follow_link"
+ * for the common case.
+ */
+static inline int do_follow_link(struct inode *inode, int follow)
+{
+        if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
+                if (likely(inode->i_op->follow_link))
+                        return follow;
+
+                /* This gets set once for the inode lifetime */
+                spin_lock(&inode->i_lock);
+                inode->i_opflags |= IOP_NOFOLLOW;
+                spin_unlock(&inode->i_lock);
+        }
+        return 0;
+}
+
 static inline int walk_component(struct nameidata *nd, struct path *path,
                 struct qstr *name, int type, int follow)
 {
@@ -1267,7 +1303,7 @@ static inline int walk_component(struct nameidata *nd, struct path *path,
                 terminate_walk(nd);
                 return -ENOENT;
         }
-        if (unlikely(inode->i_op->follow_link) && follow) {
+        if (do_follow_link(inode, follow)) {
                 if (nd->flags & LOOKUP_RCU) {
                         if (unlikely(unlazy_walk(nd, path->dentry))) {
                                 terminate_walk(nd);
@@ -1320,6 +1356,26 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd)
 }
 
 /*
+ * We really don't want to look at inode->i_op->lookup
+ * when we don't have to. So we keep a cache bit in
+ * the inode ->i_opflags field that says "yes, we can
+ * do lookup on this inode".
+ */
+static inline int can_lookup(struct inode *inode)
+{
+        if (likely(inode->i_opflags & IOP_LOOKUP))
+                return 1;
+        if (likely(!inode->i_op->lookup))
+                return 0;
+
+        /* We do this once for the lifetime of the inode */
+        spin_lock(&inode->i_lock);
+        inode->i_opflags |= IOP_LOOKUP;
+        spin_unlock(&inode->i_lock);
+        return 1;
+}
+
+/*
  * Name resolution.
  * This is the basic name resolution function, turning a pathname into
  * the final dentry. We expect 'base' to be positive and a directory.
@@ -1398,10 +1454,10 @@ static int link_path_walk(const char *name, struct nameidata *nd)
                         if (err)
                                 return err;
                 }
+                if (can_lookup(nd->inode))
+                        continue;
                 err = -ENOTDIR; 
-                if (!nd->inode->i_op->lookup)
-                        break;
-                continue;
+                break;
                 /* here ends the main loop */
 
 last_component: