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link_path_walk: nd->depth massage, part 1

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nd->stack[0] is unused until the handling of trailing symlinks and
we want to get rid of that.  Having fucked that transformation up
several times, I went for bloody pedantic series of provably equivalent
transformations.  Sorry.

Step 1: keep nd->depth higher by one in link_path_walk() - increment upon
entry, decrement on exits, adjust the arithmetics inside and surround the
calls of functions that care about nd->depth value (nd_alloc_stack(),
get_link(), put_link()) with decrement/increment pairs.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2015-05-03 20:01:27 -04:00
parent 894bc8c466
commit 071bf50137
1 changed files with 17 additions and 5 deletions
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22
fs/namei.c
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@ -1763,6 +1763,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
if (!*name)
return 0;
nd->depth++;
/* At this point we know we have a real path component. */
for(;;) {
u64 hash_len;
@ -1823,15 +1824,18 @@ Walked:
if (err) {
const char *s;
nd->depth--;
err = nd_alloc_stack(nd);
nd->depth++;
if (unlikely(err)) {
path_to_nameidata(&nd->link, nd);
break;
}
nd->depth++;
nd->depth--;
s = get_link(nd);
nd->depth++;
if (unlikely(IS_ERR(s))) {
err = PTR_ERR(s);
@ -1841,7 +1845,9 @@ Walked:
err = 0;
if (unlikely(!s)) {
/* jumped */
nd->depth--;
put_link(nd);
nd->depth++;
nd->depth--;
} else {
if (*s == '/') {
@ -1855,7 +1861,7 @@ Walked:
;
}
nd->inode = nd->path.dentry->d_inode;
nd->stack[nd->depth].name = name;
nd->stack[nd->depth - 1].name = name;
if (!*s)
goto OK;
name = s;
@ -1869,19 +1875,25 @@ Walked:
}
terminate_walk(nd);
Err:
while (unlikely(nd->depth)) {
while (unlikely(nd->depth > 1)) {
nd->depth--;
put_link(nd);
nd->depth++;
nd->depth--;
}
nd->depth--;
return err;
OK:
if (unlikely(nd->depth)) {
name = nd->stack[nd->depth].name;
if (unlikely(nd->depth > 1)) {
name = nd->stack[nd->depth - 1].name;
err = walk_component(nd, LOOKUP_FOLLOW);
nd->depth--;
put_link(nd);
nd->depth++;
nd->depth--;
goto Walked;
}
nd->depth--;
return 0;
}