sanitize path_walk() mess

New helper: path_lookupat().  Basically, what do_path_lookup() boils to
modulo -ECHILD/-ESTALE handler.  path_walk* family is gone; vfs_path_lookup()
is using link_path_walk() directly, do_path_lookup() and do_filp_open()
are using path_lookupat().

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

1 files changed, 56 insertions, 92 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 8c704465f6ce..f5de5bb1a61f 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1520,59 +1520,6 @@ return_err:
         return err;
 }
 
-static inline int path_walk_rcu(const char *name, struct nameidata *nd)
-{
-        current->total_link_count = 0;
-
-        return link_path_walk(name, nd);
-}
-
-static inline int path_walk_simple(const char *name, struct nameidata *nd)
-{
-        current->total_link_count = 0;
-
-        return link_path_walk(name, nd);
-}
-
-static int path_walk(const char *name, struct nameidata *nd)
-{
-        struct path save = nd->path;
-        int result;
-
-        current->total_link_count = 0;
-
-        /* make sure the stuff we saved doesn't go away */
-        path_get(&save);
-
-        result = link_path_walk(name, nd);
-        if (result == -ESTALE) {
-                /* nd->path had been dropped */
-                current->total_link_count = 0;
-                nd->path = save;
-                nd->inode = save.dentry->d_inode;
-                path_get(&nd->path);
-                nd->flags |= LOOKUP_REVAL;
-                result = link_path_walk(name, nd);
-        }
-
-        path_put(&save);
-
-        return result;
-}
-
-static void path_finish_rcu(struct nameidata *nd)
-{
-        if (nd->flags & LOOKUP_RCU) {
-                /* RCU dangling. Cancel it. */
-                nd->flags &= ~LOOKUP_RCU;
-                nd->root.mnt = NULL;
-                rcu_read_unlock();
-                br_read_unlock(vfsmount_lock);
-        }
-        if (nd->file)
-                fput(nd->file);
-}
-
 static int path_init_rcu(int dfd, const char *name, unsigned int flags, struct nameidata *nd)
 {
         int retval = 0;
@@ -1697,7 +1644,7 @@ out_fail:
 }
 
 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
-static int do_path_lookup(int dfd, const char *name,
+static int path_lookupat(int dfd, const char *name,
                                 unsigned int flags, struct nameidata *nd)
 {
         int retval;
@@ -1716,29 +1663,45 @@ static int do_path_lookup(int dfd, const char *name,
          * be handled by restarting a traditional ref-walk (which will always
          * be able to complete).
          */
-        retval = path_init_rcu(dfd, name, flags, nd);
+        if (flags & LOOKUP_RCU)
+                retval = path_init_rcu(dfd, name, flags, nd);
+        else
+                retval = path_init(dfd, name, flags, nd);
+
         if (unlikely(retval))
                 return retval;
-        retval = path_walk_rcu(name, nd);
-        path_finish_rcu(nd);
+
+        current->total_link_count = 0;
+        retval = link_path_walk(name, nd);
+
+        if (nd->flags & LOOKUP_RCU) {
+                /* RCU dangling. Cancel it. */
+                nd->flags &= ~LOOKUP_RCU;
+                nd->root.mnt = NULL;
+                rcu_read_unlock();
+                br_read_unlock(vfsmount_lock);
+        }
+
+        if (nd->file) {
+                fput(nd->file);
+                nd->file = NULL;
+        }
+
         if (nd->root.mnt) {
                 path_put(&nd->root);
                 nd->root.mnt = NULL;
         }
+        return retval;
+}
 
-        if (unlikely(retval == -ECHILD || retval == -ESTALE)) {
-                /* slower, locked walk */
-                if (retval == -ESTALE)
-                        flags |= LOOKUP_REVAL;
-                retval = path_init(dfd, name, flags, nd);
-                if (unlikely(retval))
-                        return retval;
-                retval = path_walk(name, nd);
-                if (nd->root.mnt) {
-                        path_put(&nd->root);
-                        nd->root.mnt = NULL;
-                }
-        }
+static int do_path_lookup(int dfd, const char *name,
+                                unsigned int flags, struct nameidata *nd)
+{
+        int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
+        if (unlikely(retval == -ECHILD))
+                retval = path_lookupat(dfd, name, flags, nd);
+        if (unlikely(retval == -ESTALE))
+                retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
 
         if (likely(!retval)) {
                 if (unlikely(!audit_dummy_context())) {
@@ -1746,7 +1709,6 @@ static int do_path_lookup(int dfd, const char *name,
                                 audit_inode(name, nd->path.dentry);
                 }
         }
-
         return retval;
 }
 
@@ -1776,7 +1738,7 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
                     const char *name, unsigned int flags,
                     struct nameidata *nd)
 {
-        int retval;
+        int result;
 
         /* same as do_path_lookup */
         nd->last_type = LAST_ROOT;
@@ -1790,15 +1752,27 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
         path_get(&nd->root);
         nd->inode = nd->path.dentry->d_inode;
 
-        retval = path_walk(name, nd);
-        if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
+        current->total_link_count = 0;
+
+        result = link_path_walk(name, nd);
+        if (result == -ESTALE) {
+                /* nd->path had been dropped */
+                current->total_link_count = 0;
+                nd->path.dentry = dentry;
+                nd->path.mnt = mnt;
+                nd->inode = dentry->d_inode;
+                path_get(&nd->path);
+                nd->flags |= LOOKUP_REVAL;
+                result = link_path_walk(name, nd);
+        }
+        if (unlikely(!result && !audit_dummy_context() && nd->path.dentry &&
                                 nd->inode))
                 audit_inode(name, nd->path.dentry);
 
         path_put(&nd->root);
         nd->root.mnt = NULL;
 
-        return retval;
+        return result;
 }
 
 static struct dentry *__lookup_hash(struct qstr *name,
@@ -2483,24 +2457,14 @@ out_filp2:
 
 creat:
         /* OK, have to create the file. Find the parent. */
-        error = path_init_rcu(dfd, pathname,
-                        LOOKUP_PARENT | (flags & LOOKUP_REVAL), &nd);
-        if (error)
-                goto out_filp;
-        error = path_walk_rcu(pathname, &nd);
-        path_finish_rcu(&nd);
-        if (unlikely(error == -ECHILD || error == -ESTALE)) {
-                /* slower, locked walk */
-                if (error == -ESTALE) {
+        error = path_lookupat(dfd, pathname, LOOKUP_PARENT | LOOKUP_RCU, &nd);
+        if (unlikely(error == -ECHILD))
+                error = path_lookupat(dfd, pathname, LOOKUP_PARENT, &nd);
+        if (unlikely(error == -ESTALE)) {
 reval:
-                        flags |= LOOKUP_REVAL;
-                }
-                error = path_init(dfd, pathname,
-                                LOOKUP_PARENT | (flags & LOOKUP_REVAL), &nd);
-                if (error)
-                        goto out_filp;
-
-                error = path_walk_simple(pathname, &nd);
+                flags |= LOOKUP_REVAL;
+                error = path_lookupat(dfd, pathname,
+                                LOOKUP_PARENT | LOOKUP_REVAL, &nd);
         }
         if (unlikely(error))
                 goto out_filp;