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link_path_walk: kill the recursion

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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>
This commit is contained in:
Al Viro 2015-04-18 20:30:49 -04:00
parent bdf6cbf179
commit 32cd74685c
1 changed files with 29 additions and 11 deletions
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34
fs/namei.c
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@ -1711,8 +1711,14 @@ static inline u64 hash_name(const char *name)
*/ */
static int link_path_walk(const char *name, struct nameidata *nd) 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; int err;
start:
while (*name=='/') while (*name=='/')
name++; name++;
if (!*name) if (!*name)
@ -1776,8 +1782,6 @@ Walked:
goto Err; goto Err;
if (err) { if (err) {
struct path link;
void *cookie;
const char *s; const char *s;
if (unlikely(current->link_count >= MAX_NESTED_LINKS)) { if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
@ -1790,22 +1794,25 @@ Walked:
nd->depth++; nd->depth++;
current->link_count++; current->link_count++;
last++;
link = nd->link; last->link = nd->link;
s = get_link(&link, nd, &cookie); s = get_link(&last->link, nd, &last->cookie);
if (unlikely(IS_ERR(s))) { if (unlikely(IS_ERR(s))) {
err = PTR_ERR(s); err = PTR_ERR(s);
current->link_count--; current->link_count--;
nd->depth--; nd->depth--;
last--;
goto Err; goto Err;
} }
err = 0; err = 0;
if (unlikely(!s)) { if (unlikely(!s)) {
/* jumped */ /* jumped */
put_link(nd, &link, cookie); put_link(nd, &last->link, last->cookie);
current->link_count--; current->link_count--;
nd->depth--; nd->depth--;
last--;
} else { } else {
if (*s == '/') { if (*s == '/') {
if (!nd->root.mnt) if (!nd->root.mnt)
@ -1816,17 +1823,24 @@ Walked:
nd->flags |= LOOKUP_JUMPED; nd->flags |= LOOKUP_JUMPED;
} }
nd->inode = nd->path.dentry->d_inode; 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)) { if (unlikely(err)) {
put_link(nd, &link, cookie); put_link(nd, &last->link, last->cookie);
current->link_count--; current->link_count--;
nd->depth--; nd->depth--;
last--;
goto Err; goto Err;
} else { } else {
err = walk_component(nd, LOOKUP_FOLLOW); err = walk_component(nd, LOOKUP_FOLLOW);
put_link(nd, &link, cookie); put_link(nd, &last->link, last->cookie);
current->link_count--; current->link_count--;
nd->depth--; nd->depth--;
last--;
goto Walked; goto Walked;
} }
} }
@ -1838,9 +1852,13 @@ Walked:
} }
terminate_walk(nd); terminate_walk(nd);
Err: Err:
if (likely(!nd->depth))
return err; return err;
goto back;
OK: OK:
if (likely(!nd->depth))
return 0; return 0;
goto back;
} }
static int path_init(int dfd, const struct filename *name, unsigned int flags, static int path_init(int dfd, const struct filename *name, unsigned int flags,