Commit 4693a547 authored by Al Viro's avatar Al Viro
Browse files

namei: new calling conventions for walk_component() 



instead of a single flag (!= 0 => we want to follow symlinks) pass
two bits - WALK_GET (want to follow symlinks) and WALK_PUT (put_link()
once we are done looking at the name).  The latter matters only for
success exits - on failure the caller will discard everything anyway.

Suggestions for better variant are welcome; what this thing aims for
is making sure that pending put_link() is done *before* walk_component()
decides to pick a symlink up, rather than between picking it up and
acting upon it.  See the next commit for payoff.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 8620c238

fs/namei.c

+20 −10
Original line number Diff line number Diff line
@@ -1577,7 +1577,9 @@ 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, int follow)

enum {WALK_GET = 1, WALK_PUT = 2};



static int walk_component(struct nameidata *nd, int flags)

{

	struct path path;

	struct inode *inode;
@@ -1587,8 +1589,12 @@ static int walk_component(struct nameidata *nd, int follow) 
	 * to be able to know about the current root directory and

	 * parent relationships.

	 */

	if (unlikely(nd->last_type != LAST_NORM))

		return handle_dots(nd, nd->last_type);

	if (unlikely(nd->last_type != LAST_NORM)) {

		err = handle_dots(nd, nd->last_type);

		if (flags & WALK_PUT)

			put_link(nd);

		return err;

	}

	err = lookup_fast(nd, &path, &inode);

	if (unlikely(err)) {

		if (err < 0)
@@ -1604,7 +1610,9 @@ static int walk_component(struct nameidata *nd, int follow) 
			goto out_path_put;

	}



	if (should_follow_link(path.dentry, follow)) {

	if (flags & WALK_PUT)

		put_link(nd);

	if (should_follow_link(path.dentry, flags & WALK_GET)) {

		if (nd->flags & LOOKUP_RCU) {

			if (unlikely(nd->path.mnt != path.mnt ||

				     unlazy_walk(nd, path.dentry))) {
@@ -1816,10 +1824,9 @@ OK: 
			if (!name)

				return 0;

			/* last component of nested symlink */

			err = walk_component(nd, LOOKUP_FOLLOW);

			put_link(nd);

			err = walk_component(nd, WALK_GET | WALK_PUT);

		} else {

			err = walk_component(nd, LOOKUP_FOLLOW);

			err = walk_component(nd, WALK_GET);

		}

		if (err < 0)

			break;
@@ -2017,9 +2024,12 @@ static inline int lookup_last(struct nameidata *nd) 
		nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;



	nd->flags &= ~LOOKUP_PARENT;

	err = walk_component(nd, nd->flags & LOOKUP_FOLLOW);

	if (nd->depth)

		put_link(nd);

	err = walk_component(nd,

			nd->flags & LOOKUP_FOLLOW

				? nd->depth

					? WALK_PUT | WALK_GET

					: WALK_GET

				: 0);

	if (err < 0)

		terminate_walk(nd);

	return err;

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