Cache root in nameidata
New field: nd->root. When pathname resolution wants to know the root,
check if nd->root.mnt is non-NULL; use nd->root if it is, otherwise
copy current->fs->root there. After path_walk() is finished, we check
if we'd got a cached value in nd->root and drop it. Before calling
path_walk() we should either set nd->root.mnt to NULL *or* copy (and
pin down) some path to nd->root. In the latter case we won't be
looking at current->fs->root at all.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/namei.c b/fs/namei.c
index 895733e..88baaf2 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -552,6 +552,17 @@
return result;
}
+static __always_inline void set_root(struct nameidata *nd)
+{
+ if (!nd->root.mnt) {
+ struct fs_struct *fs = current->fs;
+ read_lock(&fs->lock);
+ nd->root = fs->root;
+ path_get(&nd->root);
+ read_unlock(&fs->lock);
+ }
+}
+
static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
{
int res = 0;
@@ -560,14 +571,10 @@
goto fail;
if (*link == '/') {
- struct fs_struct *fs = current->fs;
-
+ set_root(nd);
path_put(&nd->path);
-
- read_lock(&fs->lock);
- nd->path = fs->root;
- path_get(&fs->root);
- read_unlock(&fs->lock);
+ nd->path = nd->root;
+ path_get(&nd->root);
}
res = link_path_walk(link, nd);
@@ -741,19 +748,16 @@
static __always_inline void follow_dotdot(struct nameidata *nd)
{
- struct fs_struct *fs = current->fs;
+ set_root(nd);
while(1) {
struct vfsmount *parent;
struct dentry *old = nd->path.dentry;
- read_lock(&fs->lock);
- if (nd->path.dentry == fs->root.dentry &&
- nd->path.mnt == fs->root.mnt) {
- read_unlock(&fs->lock);
+ if (nd->path.dentry == nd->root.dentry &&
+ nd->path.mnt == nd->root.mnt) {
break;
}
- read_unlock(&fs->lock);
spin_lock(&dcache_lock);
if (nd->path.dentry != nd->path.mnt->mnt_root) {
nd->path.dentry = dget(nd->path.dentry->d_parent);
@@ -1022,18 +1026,18 @@
int retval = 0;
int fput_needed;
struct file *file;
- struct fs_struct *fs = current->fs;
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags;
nd->depth = 0;
+ nd->root.mnt = NULL;
if (*name=='/') {
- read_lock(&fs->lock);
- nd->path = fs->root;
- path_get(&fs->root);
- read_unlock(&fs->lock);
+ set_root(nd);
+ nd->path = nd->root;
+ path_get(&nd->root);
} else if (dfd == AT_FDCWD) {
+ struct fs_struct *fs = current->fs;
read_lock(&fs->lock);
nd->path = fs->pwd;
path_get(&fs->pwd);
@@ -1079,6 +1083,10 @@
if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
nd->path.dentry->d_inode))
audit_inode(name, nd->path.dentry);
+ if (nd->root.mnt) {
+ path_put(&nd->root);
+ nd->root.mnt = NULL;
+ }
return retval;
}
@@ -1115,6 +1123,7 @@
nd->last_type = LAST_ROOT;
nd->flags = flags;
nd->depth = 0;
+ nd->root.mnt = NULL;
nd->path.dentry = dentry;
nd->path.mnt = mnt;
@@ -1125,8 +1134,12 @@
nd->path.dentry->d_inode))
audit_inode(name, nd->path.dentry);
- return retval;
+ if (nd->root.mnt) {
+ path_put(&nd->root);
+ nd->root.mnt = NULL;
+ }
+ return retval;
}
/**
@@ -1817,6 +1830,8 @@
if (!IS_ERR(nd.intent.open.file))
release_open_intent(&nd);
exit_parent:
+ if (nd.root.mnt)
+ path_put(&nd.root);
path_put(&nd.path);
return ERR_PTR(error);