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Subject[PATCH 32/79] namei: introduce nameidata->link
Date
From: Al Viro <viro@zeniv.linux.org.uk>

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>
---
fs/namei.c | 62 ++++++++++++++++++++++++++++++++++----------------------------
1 file changed, 34 insertions(+), 28 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index dbcbe42..72a6130 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -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;
@@ -1551,8 +1554,9 @@ 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;
/*
@@ -1562,38 +1566,39 @@ 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;
@@ -1606,12 +1611,12 @@ out_err:
* 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;
}
@@ -1621,13 +1626,13 @@ 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);

@@ -1762,7 +1767,6 @@ 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=='/')
@@ -1822,17 +1826,17 @@ 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;
}
}
@@ -1952,20 +1956,19 @@ 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;

/*
@@ -1984,10 +1987,10 @@ 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;
@@ -1995,7 +1998,7 @@ 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);
}
}
@@ -2304,8 +2307,10 @@ done:
}
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;
@@ -3034,6 +3039,7 @@ finish_lookup:
}
}
BUG_ON(inode != path->dentry->d_inode);
+ nd->link = *path;
return 1;
}

@@ -3222,7 +3228,7 @@ 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))
--
2.1.4


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