Look up dfd in set_nameidata() if not AT_FDCWD and store the resultant
fd_cookie in struct nameidata. LOOKUP_AT_FDCWD is set if AT_FDCWD was
supplied. The fd_cookie is released in restore_nameidata().
This means that where the fd points in a construct like the following:
set_nameidata(&nd, dfd, name);
retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
if (unlikely(retval == -ECHILD))
retval = path_lookupat(&nd, flags, path);
if (unlikely(retval == -ESTALE))
retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
doesn't change between the three calls to path_lookupat() or similar.
It also allows us to fish the fd_cookie out for the upcoming move_mount()
syscall which needs to clear a file flag if successful.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
fs/namei.c | 38 +++++++++++++++++++++-----------------
1 file changed, 21 insertions(+), 17 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 6f0dc40f88c5..819d6ee71b46 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -53,8 +53,8 @@
* The new code replaces the old recursive symlink resolution with
* an iterative one (in case of non-nested symlink chains). It does
* this with calls to <fs>_follow_link().
- * As a side effect, dir_namei(), _namei() and follow_link() are now
- * replaced with a single function lookup_dentry() that can handle all
+ * As a side effect, dir_namei(), _namei() and follow_link() are now
+ * replaced with a single function lookup_dentry() that can handle all
* the special cases of the former code.
*
* With the new dcache, the pathname is stored at each inode, at least as
@@ -506,25 +506,34 @@ struct nameidata {
struct filename *name;
struct nameidata *saved;
struct inode *link_inode;
+ struct fd_cookie *dfd;
+ bool have_dfd;
unsigned root_seq;
- int dfd;
} __randomize_layout;
static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
{
struct nameidata *old = current->nameidata;
p->stack = p->internal;
- p->dfd = dfd;
p->name = name;
p->total_link_count = old ? old->total_link_count : 0;
p->saved = old;
current->nameidata = p;
+
+ if (likely(dfd == AT_FDCWD)) {
+ p->dfd = NULL;
+ p->have_dfd = false;
+ } else {
+ p->dfd = __fdget_raw(dfd); /* Error are dealt with later */
+ p->have_dfd = true;
+ }
}
static void restore_nameidata(void)
{
struct nameidata *now = current->nameidata, *old = now->saved;
+ __fdput(now->dfd);
current->nameidata = old;
if (old)
old->total_link_count = now->total_link_count;
@@ -2165,7 +2174,7 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->root.mnt = NULL;
rcu_read_unlock();
return ERR_PTR(-ECHILD);
- } else if (nd->dfd == AT_FDCWD) {
+ } else if (!nd->have_dfd) {
if (flags & LOOKUP_RCU) {
struct fs_struct *fs = current->fs;
unsigned seq;
@@ -2185,22 +2194,18 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
return s;
} else {
/* Caller must check execute permissions on the starting path component */
- struct fd f = fdget_raw(nd->dfd);
struct dentry *dentry;
+ struct file *file = __fdfile(nd->dfd);
- if (!f.file)
+ if (!nd->dfd)
return ERR_PTR(-EBADF);
- dentry = f.file->f_path.dentry;
+ dentry = file->f_path.dentry;
- if (*s) {
- if (!d_can_lookup(dentry)) {
- fdput(f);
- return ERR_PTR(-ENOTDIR);
- }
- }
+ if (*s && !d_can_lookup(dentry))
+ return ERR_PTR(-ENOTDIR);
- nd->path = f.file->f_path;
+ nd->path = file->f_path;
if (flags & LOOKUP_RCU) {
rcu_read_lock();
nd->inode = nd->path.dentry->d_inode;
@@ -2209,7 +2214,6 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
path_get(&nd->path);
nd->inode = nd->path.dentry->d_inode;
}
- fdput(f);
return s;
}
}
@@ -3557,7 +3561,7 @@ struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
if (IS_ERR(filename))
return ERR_CAST(filename);
- set_nameidata(&nd, -1, filename);
+ set_nameidata(&nd, AT_FDCWD, filename);
file = path_openat(&nd, op, flags | LOOKUP_RCU);
if (unlikely(file == ERR_PTR(-ECHILD)))
file = path_openat(&nd, op, flags);
