[PATCH 20/24] namei: introduce nameidata->stack

Al Viro
2015-04-20T18:13:36Z

From: Al Viro <viro@zeniv.linux.org.uk>

move the stack of saved states out of link_path_walk() stack frame to
that of callers, put a reference to it into struct nameidata as
nd->stack, move nd->saved_names[] elements in there.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/namei.c | 35 ++++++++++++++++++++++++-----------
1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index e03c18f..1c967d1 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -504,7 +504,12 @@ struct nameidata {
int link_count,
total_link_count;
struct file *base;
- char *saved_names[MAX_NESTED_LINKS + 1];
+ struct saved {
+ struct path link;
+ const char *name;
+ void *cookie;
+ char *body;
+ } *stack;
};

static struct nameidata *set_nameidata(struct nameidata *p)
@@ -738,13 +743,13 @@ void nd_set_link(char *path)
{
struct nameidata *nd = current->nameidata;

- nd->saved_names[nd->depth] = path;
+ nd->stack[nd->depth].body = path;
}
EXPORT_SYMBOL(nd_set_link);

static inline char *nd_get_link(struct nameidata *nd)
{
- return nd->saved_names[nd->depth];
+ return nd->stack[nd->depth].body;
}

static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
@@ -1770,11 +1775,7 @@ 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;
+ struct saved *last = nd->stack;
struct path next;
int err;

@@ -2092,7 +2093,11 @@ static int filename_lookup(int dfd, struct filename *name,
unsigned int flags, struct nameidata *nd)
{
int retval;
- struct nameidata *saved_nd = set_nameidata(nd);
+ struct saved stack[MAX_NESTED_LINKS + 1];
+ struct nameidata *saved_nd;
+
+ nd->stack = stack;
+ saved_nd = set_nameidata(nd);

retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
if (unlikely(retval == -ECHILD))
@@ -2409,9 +2414,12 @@ static int
path_mountpoint(int dfd, const struct filename *name, struct path *path,
unsigned int flags)
{
- struct nameidata nd, *saved = set_nameidata(&nd);
+ struct saved stack[MAX_NESTED_LINKS + 1];
+ struct nameidata nd, *saved;
int err;

+ nd.stack = stack;
+ saved = set_nameidata(&nd);
err = path_init(dfd, name, flags, &nd);
if (unlikely(err))
goto out;
@@ -3280,6 +3288,7 @@ static struct file *path_openat(int dfd, struct filename *pathname,
struct path path;
int opened = 0;
int error;
+ struct saved stack[MAX_NESTED_LINKS + 1];
struct nameidata *saved_nd;

file = get_empty_filp();
@@ -3287,6 +3296,7 @@ static struct file *path_openat(int dfd, struct filename *pathname,
return file;

file->f_flags = op->open_flag;
+ nd->stack = stack;
saved_nd = set_nameidata(nd);

if (unlikely(file->f_flags & __O_TMPFILE)) {
@@ -4491,11 +4501,14 @@ EXPORT_SYMBOL(readlink_copy);
*/
int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
- struct nameidata nd, *saved = set_nameidata(&nd);
+ struct saved stack;
+ struct nameidata nd, *saved;
void *cookie;
int res;

nd.depth = 0;
+ nd.stack = &stack;
+ saved = set_nameidata(&nd);
cookie = dentry->d_inode->i_op->follow_link(dentry);
if (IS_ERR(cookie))
res = PTR_ERR(cookie);
--
2.1.4