Commit 2a737871 authored by Al Viro's avatar Al Viro
Browse files

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: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 9b4a9b14

fs/namei.c

+34 −19
Original line number Diff line number Diff line
@@ -552,6 +552,17 @@ static __always_inline int link_path_walk(const char *name, struct nameidata *nd 
	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 @@ static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *l 
		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 @@ int follow_down(struct vfsmount **mnt, struct dentry **dentry) 


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 @@ static int path_init(int dfd, const char *name, unsigned int flags, struct namei 
	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 @@ static int do_path_lookup(int dfd, const char *name, 
	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 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, 
	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 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, 
				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 @@ exit: 
	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);

include/linux/namei.h

+1 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ enum { MAX_NESTED_LINKS = 8 }; 
struct nameidata {

	struct path	path;

	struct qstr	last;

	struct path	root;

	unsigned int	flags;

	int		last_type;

	unsigned	depth;

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