merge handle_reval_dot and nameidata_drop_rcu_last

new helper: complete_walk().  Done on successful completion
of walk, drops out of RCU mode, does d_revalidate of final
result if that hadn't been done already.

handle_reval_dot() and nameidata_drop_rcu_last() subsumed into
that one; callers converted to use of complete_walk().

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

1 files changed, 40 insertions, 81 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 1039cbae0c12..9f594312d486 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -469,43 +469,6 @@ err_root:
 }
 
 /**
- * nameidata_drop_rcu_last - drop nameidata ending path walk out of rcu-walk
- * @nd: nameidata pathwalk data to drop
- * Returns: 0 on success, -ECHILD on failure
- *
- * nameidata_drop_rcu_last attempts to drop the current nd->path into ref-walk.
- * nd->path should be the final element of the lookup, so nd->root is discarded.
- * Must be called from rcu-walk context.
- */
-static int nameidata_drop_rcu_last(struct nameidata *nd)
-{
-        struct dentry *dentry = nd->path.dentry;
-
-        BUG_ON(!(nd->flags & LOOKUP_RCU));
-        nd->flags &= ~LOOKUP_RCU;
-        if (!(nd->flags & LOOKUP_ROOT))
-                nd->root.mnt = NULL;
-        spin_lock(&dentry->d_lock);
-        if (!__d_rcu_to_refcount(dentry, nd->seq))
-                goto err_unlock;
-        BUG_ON(nd->inode != dentry->d_inode);
-        spin_unlock(&dentry->d_lock);
-
-        mntget(nd->path.mnt);
-
-        rcu_read_unlock();
-        br_read_unlock(vfsmount_lock);
-
-        return 0;
-
-err_unlock:
-        spin_unlock(&dentry->d_lock);
-        rcu_read_unlock();
-        br_read_unlock(vfsmount_lock);
-        return -ECHILD;
-}
-
-/**
  * release_open_intent - free up open intent resources
  * @nd: pointer to nameidata
  */
@@ -548,26 +511,39 @@ do_revalidate(struct dentry *dentry, struct nameidata *nd)
         return dentry;
 }
 
-/*
- * handle_reval_path - force revalidation of a dentry
- *
- * In some situations the path walking code will trust dentries without
- * revalidating them. This causes problems for filesystems that depend on
- * d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
- * (which indicates that it's possible for the dentry to go stale), force
- * a d_revalidate call before proceeding.
+/**
+ * complete_walk - successful completion of path walk
+ * @nd:  pointer nameidata
  *
- * Returns 0 if the revalidation was successful. If the revalidation fails,
- * either return the error returned by d_revalidate or -ESTALE if the
- * revalidation it just returned 0. If d_revalidate returns 0, we attempt to
- * invalidate the dentry. It's up to the caller to handle putting references
- * to the path if necessary.
+ * If we had been in RCU mode, drop out of it and legitimize nd->path.
+ * Revalidate the final result, unless we'd already done that during
+ * the path walk or the filesystem doesn't ask for it.  Return 0 on
+ * success, -error on failure.  In case of failure caller does not
+ * need to drop nd->path.
  */
-static inline int handle_reval_path(struct nameidata *nd)
+static int complete_walk(struct nameidata *nd)
 {
         struct dentry *dentry = nd->path.dentry;
         int status;
 
+        if (nd->flags & LOOKUP_RCU) {
+                nd->flags &= ~LOOKUP_RCU;
+                if (!(nd->flags & LOOKUP_ROOT))
+                        nd->root.mnt = NULL;
+                spin_lock(&dentry->d_lock);
+                if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
+                        spin_unlock(&dentry->d_lock);
+                        rcu_read_unlock();
+                        br_read_unlock(vfsmount_lock);
+                        return -ECHILD;
+                }
+                BUG_ON(nd->inode != dentry->d_inode);
+                spin_unlock(&dentry->d_lock);
+                mntget(nd->path.mnt);
+                rcu_read_unlock();
+                br_read_unlock(vfsmount_lock);
+        }
+
         if (likely(!(nd->flags & LOOKUP_JUMPED)))
                 return 0;
 
@@ -585,6 +561,7 @@ static inline int handle_reval_path(struct nameidata *nd)
         if (!status)
                 status = -ESTALE;
 
+        path_put(&nd->path);
         return status;
 }
 
@@ -1598,18 +1575,8 @@ static int path_lookupat(int dfd, const char *name,
                 }
         }
 
-        if (nd->flags & LOOKUP_RCU) {
-                /* went all way through without dropping RCU */
-                BUG_ON(err);
-                if (nameidata_drop_rcu_last(nd))
-                        err = -ECHILD;
-        }
-
-        if (!err) {
-                err = handle_reval_path(nd);
-                if (err)
-                        path_put(&nd->path);
-        }
+        if (!err)
+                err = complete_walk(nd);
 
         if (!err && nd->flags & LOOKUP_DIRECTORY) {
                 if (!nd->inode->i_op->lookup) {
@@ -2075,13 +2042,9 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
                         return ERR_PTR(error);
                 /* fallthrough */
         case LAST_ROOT:
-                if (nd->flags & LOOKUP_RCU) {
-                        if (nameidata_drop_rcu_last(nd))
-                                return ERR_PTR(-ECHILD);
-                }
-                error = handle_reval_path(nd);
+                error = complete_walk(nd);
                 if (error)
-                        goto exit;
+                        return ERR_PTR(error);
                 audit_inode(pathname, nd->path.dentry);
                 if (open_flag & O_CREAT) {
                         error = -EISDIR;
@@ -2089,10 +2052,9 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
                 }
                 goto ok;
         case LAST_BIND:
-                /* can't be RCU mode here */
-                error = handle_reval_path(nd);
+                error = complete_walk(nd);
                 if (error)
-                        goto exit;
+                        return ERR_PTR(error);
                 audit_inode(pathname, dir);
                 goto ok;
         }
@@ -2111,10 +2073,9 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
                 if (error) /* symlink */
                         return NULL;
                 /* sayonara */
-                if (nd->flags & LOOKUP_RCU) {
-                        if (nameidata_drop_rcu_last(nd))
-                                return ERR_PTR(-ECHILD);
-                }
+                error = complete_walk(nd);
+                if (error)
+                        return ERR_PTR(-ECHILD);
 
                 error = -ENOTDIR;
                 if (nd->flags & LOOKUP_DIRECTORY) {
@@ -2126,11 +2087,9 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
         }
 
         /* create side of things */
-
-        if (nd->flags & LOOKUP_RCU) {
-                if (nameidata_drop_rcu_last(nd))
-                        return ERR_PTR(-ECHILD);
-        }
+        error = complete_walk(nd);
+        if (error)
+                return ERR_PTR(error);
 
         audit_inode(pathname, dir);
         error = -EISDIR;