link_path_walk: kill the recursion

absolutely straightforward now - the only variables we need to preserve
across the recursive call are name, link and cookie, and recursion depth
is limited (and can is equal to nd->depth).  So arrange an array of
triples to hold instances of those and be done with that.

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

diff --git a/fs/namei.c b/fs/namei.c
index b469ce2..9844bb2 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1711,8 +1711,14 @@ static inline u64 hash_name(const char *name)
  */
 static int link_path_walk(const char *name, struct nameidata *nd)
 {
+       struct saved {
+               struct path link;
+               void *cookie;
+               const char *name;
+       } stack[MAX_NESTED_LINKS], *last = stack + nd->depth - 1;
        int err;
-       
+
+start:
        while (*name=='/')
                name++;
        if (!*name)
@@ -1776,8 +1782,6 @@ Walked:
                        goto Err;
 
                if (err) {
-                       struct path link;
-                       void *cookie;
                        const char *s;
 
                        if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
@@ -1790,22 +1794,25 @@ Walked:
 
                        nd->depth++;
                        current->link_count++;
+                       last++;
 
-                       link = nd->link;
-                       s = get_link(&link, nd, &cookie);
+                       last->link = nd->link;
+                       s = get_link(&last->link, nd, &last->cookie);
 
                        if (unlikely(IS_ERR(s))) {
                                err = PTR_ERR(s);
                                current->link_count--;
                                nd->depth--;
+                               last--;
                                goto Err;
                        }
                        err = 0;
                        if (unlikely(!s)) {
                                /* jumped */
-                               put_link(nd, &link, cookie);
+                               put_link(nd, &last->link, last->cookie);
                                current->link_count--;
                                nd->depth--;
+                               last--;
                        } else {
                                if (*s == '/') {
                                        if (!nd->root.mnt)
@@ -1816,17 +1823,24 @@ Walked:
                                        nd->flags |= LOOKUP_JUMPED;
                                }
                                nd->inode = nd->path.dentry->d_inode;
-                               err = link_path_walk(s, nd);
+                               last->name = name;
+                               name = s;
+                               goto start;
+
+back:
+                               name = last->name;
                                if (unlikely(err)) {
-                                       put_link(nd, &link, cookie);
+                                       put_link(nd, &last->link, last->cookie);
                                        current->link_count--;
                                        nd->depth--;
+                                       last--;
                                        goto Err;
                                } else {
                                        err = walk_component(nd, LOOKUP_FOLLOW);
-                                       put_link(nd, &link, cookie);
+                                       put_link(nd, &last->link, last->cookie);
                                        current->link_count--;
                                        nd->depth--;
+                                       last--;
                                        goto Walked;
                                }
                        }
@@ -1838,9 +1852,13 @@ Walked:
        }
        terminate_walk(nd);
 Err:
-       return err;
+       if (likely(!nd->depth))
+               return err;
+       goto back;
 OK:
-       return 0;
+       if (likely(!nd->depth))
+               return 0;
+       goto back;
 }
 
 static int path_init(int dfd, const struct filename *name, unsigned int flags,