d_path: saner calling conventions for __dentry_path()

1) lift NUL-termination into the callers
2) pass pointer to the end of buffer instead of that to beginning.

(1) allows to simplify dentry_path() - we don't need to play silly
games with restoring the leading / of "//deleted" after __dentry_path()
would've overwritten it with NUL.

We also do not need to check if (either) prepend() in there fails -
if the buffer is not large enough, we'll end with negative buflen
after prepend() and __dentry_path() will return the right value
(ERR_PTR(-ENAMETOOLONG)) just fine.

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

diff --git a/fs/d_path.c b/fs/d_path.c
index 01df5df..1a1cf05 100644 (file)
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -326,22 +326,21 @@ char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
 /*
  * Write full pathname from the root of the filesystem into the buffer.
  */
-static char *__dentry_path(const struct dentry *d, char *buf, int buflen)
+static char *__dentry_path(const struct dentry *d, char *p, int buflen)
 {
        const struct dentry *dentry;
        char *end, *retval;
        int len, seq = 0;
        int error = 0;
 
-       if (buflen < 2)
+       if (buflen < 1)
                goto Elong;
 
        rcu_read_lock();
 restart:
        dentry = d;
-       end = buf + buflen;
+       end = p;
        len = buflen;
-       prepend(&end, &len, "", 1);
        /* Get '/' right */
        retval = end-1;
        *retval = '/';
@@ -373,27 +372,21 @@ Elong:
 
 char *dentry_path_raw(const struct dentry *dentry, char *buf, int buflen)
 {
-       return __dentry_path(dentry, buf, buflen);
+       char *p = buf + buflen;
+       prepend(&p, &buflen, "", 1);
+       return __dentry_path(dentry, p, buflen);
 }
 EXPORT_SYMBOL(dentry_path_raw);
 
 char *dentry_path(const struct dentry *dentry, char *buf, int buflen)
 {
-       char *p = NULL;
-       char *retval;
-
-       if (d_unlinked(dentry)) {
-               p = buf + buflen;
-               if (prepend(&p, &buflen, "//deleted", 10) != 0)
-                       goto Elong;
-               buflen++;
-       }
-       retval = __dentry_path(dentry, buf, buflen);
-       if (!IS_ERR(retval) && p)
-               *p = '/';       /* restore '/' overriden with '\0' */
-       return retval;
-Elong:
-       return ERR_PTR(-ENAMETOOLONG);
+       char *p = buf + buflen;
+
+       if (unlikely(d_unlinked(dentry)))
+               prepend(&p, &buflen, "//deleted", 10);
+       else
+               prepend(&p, &buflen, "", 1);
+       return __dentry_path(dentry, p, buflen);
 }
 
 static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,