namei: teach lookup_slow() to skip revalidate

... and make mountpoint_last() use it.  That makes all
candidates for lookup with parent locked shared go
through lookup_slow().

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

2 files changed, 36 insertions, 23 deletions

diff --git a/fs/namei.c b/fs/namei.c
index cb70a817d439..dbb8ec1a2006 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1605,7 +1605,29 @@ static struct dentry *lookup_slow(const struct qstr *name,
 {
         struct dentry *dentry;
         inode_lock(dir->d_inode);
-        dentry = __lookup_hash(name, dir, flags);
+        dentry = d_lookup(dir, name);
+        if (unlikely(dentry)) {
+                if ((dentry->d_flags & DCACHE_OP_REVALIDATE) &&
+                    !(flags & LOOKUP_NO_REVAL)) {
+                        int error = d_revalidate(dentry, flags);
+                        if (unlikely(error <= 0)) {
+                                if (!error)
+                                        d_invalidate(dentry);
+                                dput(dentry);
+                                dentry = ERR_PTR(error);
+                        }
+                }
+                if (dentry) {
+                        inode_unlock(dir->d_inode);
+                        return dentry;
+                }
+        }
+        dentry = d_alloc(dir, name);
+        if (unlikely(!dentry)) {
+                inode_unlock(dir->d_inode);
+                return ERR_PTR(-ENOMEM);
+        }
+        dentry = lookup_real(dir->d_inode, dentry, flags);
         inode_unlock(dir->d_inode);
         return dentry;
 }
@@ -2425,31 +2447,21 @@ mountpoint_last(struct nameidata *nd, struct path *path)
                 if (error)
                         return error;
                 dentry = dget(nd->path.dentry);
-                goto done;
-        }
-
-        inode_lock(dir->d_inode);
-        dentry = d_lookup(dir, &nd->last);
-        if (!dentry) {
-                /*
-                 * No cached dentry. Mounted dentries are pinned in the cache,
-                 * so that means that this dentry is probably a symlink or the
-                 * path doesn't actually point to a mounted dentry.
-                 */
-                dentry = d_alloc(dir, &nd->last);
+        } else {
+                dentry = d_lookup(dir, &nd->last);
                 if (!dentry) {
-                        inode_unlock(dir->d_inode);
-                        return -ENOMEM;
-                }
-                dentry = lookup_real(dir->d_inode, dentry, nd->flags);
-                if (IS_ERR(dentry)) {
-                        inode_unlock(dir->d_inode);
-                        return PTR_ERR(dentry);
+                        /*
+                         * No cached dentry. Mounted dentries are pinned in the
+                         * cache, so that means that this dentry is probably
+                         * a symlink or the path doesn't actually point
+                         * to a mounted dentry.
+                         */
+                        dentry = lookup_slow(&nd->last, dir,
+                                             nd->flags | LOOKUP_NO_REVAL);
+                        if (IS_ERR(dentry))
+                                return PTR_ERR(dentry);
                 }
         }
-        inode_unlock(dir->d_inode);
-
-done:
         if (d_is_negative(dentry)) {
                 dput(dentry);
                 return -ENOENT;
diff --git a/include/linux/namei.h b/include/linux/namei.h
index d0f25d81b46a..77d01700daf7 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -31,6 +31,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
 #define LOOKUP_PARENT           0x0010
 #define LOOKUP_REVAL            0x0020
 #define LOOKUP_RCU              0x0040
+#define LOOKUP_NO_REVAL         0x0080
 
 /*
  * Intent data