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>

1 files changed, 29 insertions, 11 deletions

diff --git a/fs/namei.c b/fs/namei.c
index b469ce26ff74..9844bb2f041f 100644
--- 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,