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namei: introduce nameidata->link

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shares space with nameidata->next, walk_component() et.al. store
the struct path of symlink instead of returning it into a variable
passed by caller.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2015-04-22 17:52:47 -04:00
parent d4dee48bad
commit caa8563443
1 changed files with 34 additions and 28 deletions
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62
fs/namei.c
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@ -494,7 +494,10 @@ EXPORT_SYMBOL(path_put);
struct nameidata {
struct path path;
struct qstr last;
union {
struct qstr last;
struct path link;
};
struct path root;
struct inode *inode; /* path.dentry.d_inode */
unsigned int flags;
@ -1559,8 +1562,9 @@ static inline int should_follow_link(struct dentry *dentry, int follow)
return unlikely(d_is_symlink(dentry)) ? follow : 0;
}
static int walk_component(struct nameidata *nd, struct path *path, int follow)
static int walk_component(struct nameidata *nd, int follow)
{
struct path path;
struct inode *inode;
int err;
/*
@ -1570,38 +1574,39 @@ static int walk_component(struct nameidata *nd, struct path *path, int follow)
*/
if (unlikely(nd->last_type != LAST_NORM))
return handle_dots(nd, nd->last_type);
err = lookup_fast(nd, path, &inode);
err = lookup_fast(nd, &path, &inode);
if (unlikely(err)) {
if (err < 0)
goto out_err;
err = lookup_slow(nd, path);
err = lookup_slow(nd, &path);
if (err < 0)
goto out_err;
inode = path->dentry->d_inode;
inode = path.dentry->d_inode;
err = -ENOENT;
if (d_is_negative(path->dentry))
if (d_is_negative(path.dentry))
goto out_path_put;
}
if (should_follow_link(path->dentry, follow)) {
if (should_follow_link(path.dentry, follow)) {
if (nd->flags & LOOKUP_RCU) {
if (unlikely(nd->path.mnt != path->mnt ||
unlazy_walk(nd, path->dentry))) {
if (unlikely(nd->path.mnt != path.mnt ||
unlazy_walk(nd, path.dentry))) {
err = -ECHILD;
goto out_err;
}
}
BUG_ON(inode != path->dentry->d_inode);
BUG_ON(inode != path.dentry->d_inode);
nd->link = path;
return 1;
}
path_to_nameidata(path, nd);
path_to_nameidata(&path, nd);
nd->inode = inode;
return 0;
out_path_put:
path_to_nameidata(path, nd);
path_to_nameidata(&path, nd);
out_err:
terminate_walk(nd);
return err;
@ -1614,12 +1619,12 @@ static int walk_component(struct nameidata *nd, struct path *path, int follow)
* Without that kind of total limit, nasty chains of consecutive
* symlinks can cause almost arbitrarily long lookups.
*/
static inline int nested_symlink(struct path *path, struct nameidata *nd)
static inline int nested_symlink(struct nameidata *nd)
{
int res;
if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
path_put_conditional(path, nd);
path_put_conditional(&nd->link, nd);
path_put(&nd->path);
return -ELOOP;
}
@ -1629,13 +1634,13 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd)
current->link_count++;
do {
struct path link = *path;
struct path link = nd->link;
void *cookie;
res = follow_link(&link, nd, &cookie);
if (res)
break;
res = walk_component(nd, path, LOOKUP_FOLLOW);
res = walk_component(nd, LOOKUP_FOLLOW);
put_link(nd, &link, cookie);
} while (res > 0);
@ -1770,7 +1775,6 @@ static inline u64 hash_name(const char *name)
*/
static int link_path_walk(const char *name, struct nameidata *nd)
{
struct path next;
int err;
while (*name=='/')
@ -1830,17 +1834,17 @@ static int link_path_walk(const char *name, struct nameidata *nd)
if (!*name)
return 0;
err = walk_component(nd, &next, LOOKUP_FOLLOW);
err = walk_component(nd, LOOKUP_FOLLOW);
if (err < 0)
return err;
if (err) {
err = nested_symlink(&next, nd);
err = nested_symlink(nd);
if (err)
return err;
}
if (!d_can_lookup(nd->path.dentry)) {
err = -ENOTDIR;
err = -ENOTDIR;
break;
}
}
@ -1960,20 +1964,19 @@ static void path_cleanup(struct nameidata *nd)
fput(nd->base);
}
static inline int lookup_last(struct nameidata *nd, struct path *path)
static inline int lookup_last(struct nameidata *nd)
{
if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
nd->flags &= ~LOOKUP_PARENT;
return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW);
return walk_component(nd, nd->flags & LOOKUP_FOLLOW);
}
/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
static int path_lookupat(int dfd, const struct filename *name,
unsigned int flags, struct nameidata *nd)
{
struct path path;
int err;
/*
@ -1992,10 +1995,10 @@ static int path_lookupat(int dfd, const struct filename *name,
*/
err = path_init(dfd, name, flags, nd);
if (!err && !(flags & LOOKUP_PARENT)) {
err = lookup_last(nd, &path);
err = lookup_last(nd);
while (err > 0) {
void *cookie;
struct path link = path;
struct path link = nd->link;
err = may_follow_link(&link, nd);
if (unlikely(err))
break;
@ -2003,7 +2006,7 @@ static int path_lookupat(int dfd, const struct filename *name,
err = follow_link(&link, nd, &cookie);
if (err)
break;
err = lookup_last(nd, &path);
err = lookup_last(nd);
put_link(nd, &link, cookie);
}
}
@ -2312,8 +2315,10 @@ mountpoint_last(struct nameidata *nd, struct path *path)
}
path->dentry = dentry;
path->mnt = nd->path.mnt;
if (should_follow_link(dentry, nd->flags & LOOKUP_FOLLOW))
if (should_follow_link(dentry, nd->flags & LOOKUP_FOLLOW)) {
nd->link = *path;
return 1;
}
mntget(path->mnt);
follow_mount(path);
error = 0;
@ -3040,6 +3045,7 @@ static int do_last(struct nameidata *nd, struct path *path,
}
}
BUG_ON(inode != path->dentry->d_inode);
nd->link = *path;
return 1;
}
@ -3228,7 +3234,7 @@ static struct file *path_openat(int dfd, struct filename *pathname,
error = do_last(nd, &path, file, op, &opened, pathname);
while (unlikely(error > 0)) { /* trailing symlink */
struct path link = path;
struct path link = nd->link;
void *cookie;
error = may_follow_link(&link, nd);
if (unlikely(error))