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pull handling of one pathname component into a helper 

new helper: walk_component().  Handles everything except symlinks;
returns negative on error, 0 on success and 1 on symlinks we decided
to follow.  Drops out of RCU mode on such symlinks.

link_path_walk() and do_last() switched to using that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2011-03-13 19:58:58 -04:00
parent 11a7b371b6
commit ce57dfc179
1 changed files with 55 additions and 68 deletions
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123
fs/namei.c
View File

@ -785,16 +785,11 @@ __do_follow_link(const struct path *link, struct nameidata *nd, void **p)
* Without that kind of total limit, nasty chains of consecutive
* symlinks can cause almost arbitrarily long lookups.
*/
static inline int do_follow_link(struct inode *inode, struct path *path, struct nameidata *nd)
static inline int do_follow_link(struct path *path, struct nameidata *nd)
{
void *cookie;
int err = -ELOOP;
/* We drop rcu-walk here */
if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
return -ECHILD;
BUG_ON(inode != path->dentry->d_inode);
if (current->link_count >= MAX_NESTED_LINKS)
goto loop;
if (current->total_link_count >= 40)
@ -1337,6 +1332,39 @@ static void terminate_walk(struct nameidata *nd)
}
}
static inline int walk_component(struct nameidata *nd, struct path *path,
struct qstr *name, int type, int follow)
{
struct inode *inode;
int err;
/*
* "." and ".." are special - ".." especially so because it has
* to be able to know about the current root directory and
* parent relationships.
*/
if (unlikely(type != LAST_NORM))
return handle_dots(nd, type);
err = do_lookup(nd, name, path, &inode);
if (unlikely(err)) {
terminate_walk(nd);
return err;
}
if (!inode) {
path_to_nameidata(path, nd);
terminate_walk(nd);
return -ENOENT;
}
if (unlikely(inode->i_op->follow_link) && follow) {
if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
return -ECHILD;
BUG_ON(inode != path->dentry->d_inode);
return 1;
}
path_to_nameidata(path, nd);
nd->inode = inode;
return 0;
}
/*
* Name resolution.
* This is the basic name resolution function, turning a pathname into
@ -1361,7 +1389,6 @@ static int link_path_walk(const char *name, struct nameidata *nd)
/* At this point we know we have a real path component. */
for(;;) {
struct inode *inode;
unsigned long hash;
struct qstr this;
unsigned int c;
@ -1414,34 +1441,16 @@ static int link_path_walk(const char *name, struct nameidata *nd)
if (!*name)
goto last_with_slashes;
/*
* "." and ".." are special - ".." especially so because it has
* to be able to know about the current root directory and
* parent relationships.
*/
if (unlikely(type != LAST_NORM)) {
if (handle_dots(nd, type))
return -ECHILD;
continue;
}
err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
if (err < 0)
return err;
/* This does the actual lookups.. */
err = do_lookup(nd, &this, &next, &inode);
if (err)
break;
if (inode && inode->i_op->follow_link) {
err = do_follow_link(inode, &next, nd);
if (err) {
err = do_follow_link(&next, nd);
if (err)
return err;
nd->inode = nd->path.dentry->d_inode;
} else {
path_to_nameidata(&next, nd);
nd->inode = inode;
}
err = -ENOENT;
if (!nd->inode)
break;
err = -ENOTDIR;
if (!nd->inode->i_op->lookup)
break;
@ -1453,36 +1462,27 @@ last_with_slashes:
last_component:
/* Clear LOOKUP_CONTINUE iff it was previously unset */
nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
if (lookup_flags & LOOKUP_PARENT)
goto lookup_parent;
if (unlikely(type != LAST_NORM))
return handle_dots(nd, type);
err = do_lookup(nd, &this, &next, &inode);
if (err)
break;
if (inode && unlikely(inode->i_op->follow_link) &&
(lookup_flags & LOOKUP_FOLLOW)) {
err = do_follow_link(inode, &next, nd);
if (lookup_flags & LOOKUP_PARENT) {
nd->last = this;
nd->last_type = type;
return 0;
}
err = walk_component(nd, &next, &this, type,
lookup_flags & LOOKUP_FOLLOW);
if (err < 0)
return err;
if (err) {
err = do_follow_link(&next, nd);
if (err)
return err;
nd->inode = nd->path.dentry->d_inode;
} else {
path_to_nameidata(&next, nd);
nd->inode = inode;
}
err = -ENOENT;
if (!nd->inode)
break;
if (lookup_flags & LOOKUP_DIRECTORY) {
err = -ENOTDIR;
if (!nd->inode->i_op->lookup)
break;
}
return 0;
lookup_parent:
nd->last = this;
nd->last_type = type;
return 0;
}
terminate_walk(nd);
return err;
@ -2068,7 +2068,6 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
int want_write = 0;
int acc_mode = op->acc_mode;
struct file *filp;
struct inode *inode;
int error;
nd->flags &= ~LOOKUP_PARENT;
@ -2111,24 +2110,12 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
symlink_ok = 1;
/* we _can_ be in RCU mode here */
error = do_lookup(nd, &nd->last, path, &inode);
if (error) {
terminate_walk(nd);
error = walk_component(nd, path, &nd->last, LAST_NORM,
!symlink_ok);
if (error < 0)
return ERR_PTR(error);
}
if (!inode) {
path_to_nameidata(path, nd);
terminate_walk(nd);
return ERR_PTR(-ENOENT);
}
if (unlikely(inode->i_op->follow_link && !symlink_ok)) {
/* We drop rcu-walk here */
if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
return ERR_PTR(-ECHILD);
if (error) /* symlink */
return NULL;
}
path_to_nameidata(path, nd);
nd->inode = inode;
/* sayonara */
if (nd->flags & LOOKUP_RCU) {
if (nameidata_drop_rcu_last(nd))
@ -2137,7 +2124,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
error = -ENOTDIR;
if (nd->flags & LOOKUP_DIRECTORY) {
if (!inode->i_op->lookup)
if (!nd->inode->i_op->lookup)
goto exit;
}
audit_inode(pathname, nd->path.dentry);