linux-kernel - [PATCH 21/24] namei: regularize use of put_link() and follow

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Date:	Mon, 20 Apr 2015 19:13:05 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Neil Brown <neilb@...e.de>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH 21/24] namei: regularize use of put_link() and follow_link(), trim arguments

From: Al Viro <viro@...iv.linux.org.uk>

don't bother with separate variables for link and cookie in trailing
symlink loops; use nd->stack[0] for that.  That makes *all* callers
of put_link() (and follow_link()) operate on nd->stack[nd->depth].link
and nd->stack[nd->depth].cookie.  Trim the argument lists.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/namei.c | 42 ++++++++++++++++++++----------------------
 1 file changed, 20 insertions(+), 22 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 1c967d1..a8d6751 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -752,12 +752,14 @@ static inline char *nd_get_link(struct nameidata *nd)
 	return nd->stack[nd->depth].body;
 }
 
-static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
+static inline void put_link(struct nameidata *nd)
 {
-	struct inode *inode = link->dentry->d_inode;
+	struct saved *last = nd->stack + nd->depth;
+	struct inode *inode = last->link.dentry->d_inode;
 	if (inode->i_op->put_link)
-		inode->i_op->put_link(link->dentry, nd_get_link(nd), cookie);
-	path_put(link);
+		inode->i_op->put_link(last->link.dentry, last->body,
+				      last->cookie);
+	path_put(&last->link);
 }
 
 int sysctl_protected_symlinks __read_mostly = 0;
@@ -925,14 +927,16 @@ out:
 	return res;
 }
 
-static int follow_link(struct path *link, struct nameidata *nd, void **p)
+static int follow_link(struct nameidata *nd, struct path *link)
 {
 	char *s;
 	int error = may_follow_link(link, nd);
+	struct saved *last = nd->stack + nd->depth;
 	if (unlikely(error))
 		return error;
 	nd->flags |= LOOKUP_PARENT;
-	s = get_link(link, nd, p);
+	last->link = *link;
+	s = get_link(&last->link, nd, &last->cookie);
 	if (unlikely(IS_ERR(s)))
 		return PTR_ERR(s);
 	if (unlikely(!s))
@@ -948,7 +952,7 @@ static int follow_link(struct path *link, struct nameidata *nd, void **p)
 	nd->inode = nd->path.dentry->d_inode;
 	error = link_path_walk(s, nd);
 	if (unlikely(error))
-		put_link(nd, link, *p);
+		put_link(nd);
 	return error;
 }
 
@@ -1869,7 +1873,7 @@ Walked:
 			err = 0;
 			if (unlikely(!s)) {
 				/* jumped */
-				put_link(nd, &last->link, last->cookie);
+				put_link(nd);
 				nd->link_count--;
 				nd->depth--;
 				last--;
@@ -1900,7 +1904,7 @@ Walked:
 	terminate_walk(nd);
 Err:
 	while (unlikely(nd->depth)) {
-		put_link(nd, &last->link, last->cookie);
+		put_link(nd);
 		nd->link_count--;
 		nd->depth--;
 		last--;
@@ -1910,7 +1914,7 @@ OK:
 	if (unlikely(nd->depth)) {
 		name = last->name;
 		err = walk_component(nd, &next, LOOKUP_FOLLOW);
-		put_link(nd, &last->link, last->cookie);
+		put_link(nd);
 		nd->link_count--;
 		nd->depth--;
 		last--;
@@ -2065,13 +2069,11 @@ static int path_lookupat(int dfd, const struct filename *name,
 	if (!err && !(flags & LOOKUP_PARENT)) {
 		err = lookup_last(nd, &path);
 		while (err > 0) {
-			void *cookie;
-			struct path link = path;
-			err = follow_link(&link, nd, &cookie);
+			err = follow_link(nd, &path);
 			if (err)
 				break;
 			err = lookup_last(nd, &path);
-			put_link(nd, &link, cookie);
+			put_link(nd);
 		}
 	}
 
@@ -2426,13 +2428,11 @@ path_mountpoint(int dfd, const struct filename *name, struct path *path,
 
 	err = mountpoint_last(&nd, path);
 	while (err > 0) {
-		void *cookie;
-		struct path link = *path;
-		err = follow_link(&link, &nd, &cookie);
+		err = follow_link(&nd, path);
 		if (err)
 			break;
 		err = mountpoint_last(&nd, path);
-		put_link(&nd, &link, cookie);
+		put_link(&nd);
 	}
 out:
 	path_cleanup(&nd);
@@ -3310,8 +3310,6 @@ static struct file *path_openat(int dfd, struct filename *pathname,
 
 	error = do_last(nd, &path, file, op, &opened, pathname);
 	while (unlikely(error > 0)) { /* trailing symlink */
-		struct path link = path;
-		void *cookie;
 		if (!(nd->flags & LOOKUP_FOLLOW)) {
 			path_put_conditional(&path, nd);
 			path_put(&nd->path);
@@ -3319,11 +3317,11 @@ static struct file *path_openat(int dfd, struct filename *pathname,
 			break;
 		}
 		nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
-		error = follow_link(&link, nd, &cookie);
+		error = follow_link(nd, &path);
 		if (unlikely(error))
 			break;
 		error = do_last(nd, &path, file, op, &opened, pathname);
-		put_link(nd, &link, cookie);
+		put_link(nd);
 	}
 out:
 	path_cleanup(nd);
-- 
2.1.4

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