d_path: prepend_path(): lift the inner loop into a new helper

... and leave the rename_lock/mount_lock handling in prepend_path()
itself

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

diff --git a/fs/d_path.c b/fs/d_path.c
index 9a0356c..ba62987 100644 (file)
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -68,6 +68,42 @@ static bool prepend_name(struct prepend_buffer *p, const struct qstr *name)
        return true;
 }
 
+static int __prepend_path(const struct dentry *dentry, const struct mount *mnt,
+                         const struct path *root, struct prepend_buffer *p)
+{
+       while (dentry != root->dentry || &mnt->mnt != root->mnt) {
+               const struct dentry *parent = READ_ONCE(dentry->d_parent);
+
+               if (dentry == mnt->mnt.mnt_root) {
+                       struct mount *m = READ_ONCE(mnt->mnt_parent);
+                       struct mnt_namespace *mnt_ns;
+
+                       if (likely(mnt != m)) {
+                               dentry = READ_ONCE(mnt->mnt_mountpoint);
+                               mnt = m;
+                               continue;
+                       }
+                       /* Global root */
+                       mnt_ns = READ_ONCE(mnt->mnt_ns);
+                       /* open-coded is_mounted() to use local mnt_ns */
+                       if (!IS_ERR_OR_NULL(mnt_ns) && !is_anon_ns(mnt_ns))
+                               return 1;       // absolute root
+                       else
+                               return 2;       // detached or not attached yet
+               }
+
+               if (unlikely(dentry == parent))
+                       /* Escaped? */
+                       return 3;
+
+               prefetch(parent);
+               if (!prepend_name(p, &dentry->d_name))
+                       break;
+               dentry = parent;
+       }
+       return 0;
+}
+
 /**
  * prepend_path - Prepend path string to a buffer
  * @path: the dentry/vfsmount to report
@@ -89,11 +125,9 @@ static int prepend_path(const struct path *path,
                        const struct path *root,
                        struct prepend_buffer *p)
 {
-       struct dentry *dentry;
-       struct mount *mnt;
-       int error = 0;
        unsigned seq, m_seq = 0;
        struct prepend_buffer b;
+       int error;
 
        rcu_read_lock();
 restart_mnt:
@@ -102,43 +136,8 @@ restart_mnt:
        rcu_read_lock();
 restart:
        b = *p;
-       error = 0;
-       dentry = path->dentry;
-       mnt = real_mount(path->mnt);
        read_seqbegin_or_lock(&rename_lock, &seq);
-       while (dentry != root->dentry || &mnt->mnt != root->mnt) {
-               struct dentry * parent;
-
-               if (dentry == mnt->mnt.mnt_root || IS_ROOT(dentry)) {
-                       struct mount *parent = READ_ONCE(mnt->mnt_parent);
-                       struct mnt_namespace *mnt_ns;
-
-                       /* Escaped? */
-                       if (dentry != mnt->mnt.mnt_root) {
-                               error = 3;
-                               break;
-                       }
-                       /* Global root? */
-                       if (mnt != parent) {
-                               dentry = READ_ONCE(mnt->mnt_mountpoint);
-                               mnt = parent;
-                               continue;
-                       }
-                       mnt_ns = READ_ONCE(mnt->mnt_ns);
-                       /* open-coded is_mounted() to use local mnt_ns */
-                       if (!IS_ERR_OR_NULL(mnt_ns) && !is_anon_ns(mnt_ns))
-                               error = 1;      // absolute root
-                       else
-                               error = 2;      // detached or not attached yet
-                       break;
-               }
-               parent = dentry->d_parent;
-               prefetch(parent);
-               if (!prepend_name(&b, &dentry->d_name))
-                       break;
-
-               dentry = parent;
-       }
+       error = __prepend_path(path->dentry, real_mount(path->mnt), root, &b);
        if (!(seq & 1))
                rcu_read_unlock();
        if (need_seqretry(&rename_lock, seq)) {