vfs: add prepend_path() helper

Split off prepend_path() from __d_path().  This new helper takes an
end-of-buffer pointer and buffer-length pointer just like the other
prepend_* functions.  Move the " (deleted)" postfix out to __d_path().

This patch doesn't change any functionality but paves the way for the
following patches.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 58 insertions, 36 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index f1809e6b9fda..d09d93819b4d 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1905,48 +1905,30 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name)
 }
 
 /**
- * __d_path - return the path of a dentry
+ * Prepend path string to a buffer
+ *
  * @path: the dentry/vfsmount to report
  * @root: root vfsmnt/dentry (may be modified by this function)
- * @buffer: buffer to return value in
- * @buflen: buffer length
- *
- * Convert a dentry into an ASCII path name. If the entry has been deleted
- * the string " (deleted)" is appended. Note that this is ambiguous.
- *
- * Returns a pointer into the buffer or an error code if the
- * path was too long.
+ * @buffer: pointer to the end of the buffer
+ * @buflen: pointer to buffer length
  *
- * "buflen" should be positive. Caller holds the dcache_lock.
+ * Caller holds the dcache_lock.
  *
  * If path is not reachable from the supplied root, then the value of
  * root is changed (without modifying refcounts).
  */
-char *__d_path(const struct path *path, struct path *root,
-               char *buffer, int buflen)
+static int prepend_path(const struct path *path, struct path *root,
+                        char **buffer, int *buflen)
 {
         struct dentry *dentry = path->dentry;
         struct vfsmount *vfsmnt = path->mnt;
-        char *end = buffer + buflen;
-        char *retval;
+        bool slash = false;
+        int error = 0;
 
         spin_lock(&vfsmount_lock);
-        prepend(&end, &buflen, "\0", 1);
-        if (d_unlinked(dentry) &&
-                (prepend(&end, &buflen, " (deleted)", 10) != 0))
-                        goto Elong;
-
-        if (buflen < 1)
-                goto Elong;
-        /* Get '/' right */
-        retval = end-1;
-        *retval = '/';
-
-        for (;;) {
+        while (dentry != root->dentry || vfsmnt != root->mnt) {
                 struct dentry * parent;
 
-                if (dentry == root->dentry && vfsmnt == root->mnt)
-                        break;
                 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
                         /* Global root? */
                         if (vfsmnt->mnt_parent == vfsmnt) {
@@ -1958,16 +1940,22 @@ char *__d_path(const struct path *path, struct path *root,
                 }
                 parent = dentry->d_parent;
                 prefetch(parent);
-                if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) ||
-                    (prepend(&end, &buflen, "/", 1) != 0))
-                        goto Elong;
-                retval = end;
+                error = prepend_name(buffer, buflen, &dentry->d_name);
+                if (!error)
+                        error = prepend(buffer, buflen, "/", 1);
+                if (error)
+                        break;
+
+                slash = true;
                 dentry = parent;
         }
 
 out:
+        if (!error && !slash)
+                error = prepend(buffer, buflen, "/", 1);
+
         spin_unlock(&vfsmount_lock);
-        return retval;
+        return error;
 
 global_root:
         /*
@@ -1982,10 +1970,44 @@ global_root:
         root->mnt = vfsmnt;
         root->dentry = dentry;
         goto out;
+}
 
-Elong:
-        retval = ERR_PTR(-ENAMETOOLONG);
-        goto out;
+/**
+ * __d_path - return the path of a dentry
+ * @path: the dentry/vfsmount to report
+ * @root: root vfsmnt/dentry (may be modified by this function)
+ * @buffer: buffer to return value in
+ * @buflen: buffer length
+ *
+ * Convert a dentry into an ASCII path name. If the entry has been deleted
+ * the string " (deleted)" is appended. Note that this is ambiguous.
+ *
+ * Returns a pointer into the buffer or an error code if the
+ * path was too long.
+ *
+ * "buflen" should be positive. Caller holds the dcache_lock.
+ *
+ * If path is not reachable from the supplied root, then the value of
+ * root is changed (without modifying refcounts).
+ */
+char *__d_path(const struct path *path, struct path *root,
+               char *buf, int buflen)
+{
+        char *res = buf + buflen;
+        int error;
+
+        prepend(&res, &buflen, "\0", 1);
+        if (d_unlinked(path->dentry)) {
+                error = prepend(&res, &buflen, " (deleted)", 10);
+                if (error)
+                        return ERR_PTR(error);
+        }
+
+        error = prepend_path(path, root, &res, &buflen);
+        if (error)
+                return ERR_PTR(error);
+
+        return res;
 }
 
 /**