linux-kernel - [PATCH 2/9] VFS/namei: use terminate

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Message-ID: <20150305052121.23906.81777.stgit@notabene.brown>
Date:	Thu, 05 Mar 2015 16:21:21 +1100
From:	NeilBrown <neilb@...e.de>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/9] VFS/namei: use terminate_walk when symlink lookup fails.

Currently following a symlink never uses rcu-walk, so
terminate_walk isn't needed.
That will change in a future patch.  In preparation, change
some
  path_put_condtional()
  path_put()
sequences to
  path_to_nameidata()
  terminate_walk()

These sequence are identical when in ref-walk, and correct when in
rcu-walk.

Also change two path_put() calls to equivalent terminate_walk().

Signed-off-by: NeilBrown <neilb@...e.de>
---
 fs/namei.c |   40 ++++++++++++++++++++--------------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index de508a3cec42..515adc4594be 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -726,6 +726,18 @@ char *nd_get_link(struct nameidata *nd)
 }
 EXPORT_SYMBOL(nd_get_link);
 
+static void terminate_walk(struct nameidata *nd)
+{
+	if (!(nd->flags & LOOKUP_RCU)) {
+		path_put(&nd->path);
+	} else {
+		nd->flags &= ~LOOKUP_RCU;
+		if (!(nd->flags & LOOKUP_ROOT))
+			nd->root.mnt = NULL;
+		rcu_read_unlock();
+	}
+}
+
 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
 {
 	struct inode *inode = link->dentry->d_inode;
@@ -776,8 +788,8 @@ static inline int may_follow_link(struct path *link, struct nameidata *nd)
 		return 0;
 
 	audit_log_link_denied("follow_link", link);
-	path_put_conditional(link, nd);
-	path_put(&nd->path);
+	path_to_nameidata(link, nd);
+	terminate_walk(nd);
 	return -EACCES;
 }
 
@@ -886,7 +898,7 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
 	s = nd_get_link(nd);
 	if (s) {
 		if (unlikely(IS_ERR(s))) {
-			path_put(&nd->path);
+			terminate_walk(nd);
 			put_link(nd, link, *p);
 			return PTR_ERR(s);
 		}
@@ -908,7 +920,7 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
 
 out_put_nd_path:
 	*p = NULL;
-	path_put(&nd->path);
+	terminate_walk(nd);
 	path_put(link);
 	return error;
 }
@@ -1539,18 +1551,6 @@ static inline int handle_dots(struct nameidata *nd, int type)
 	return 0;
 }
 
-static void terminate_walk(struct nameidata *nd)
-{
-	if (!(nd->flags & LOOKUP_RCU)) {
-		path_put(&nd->path);
-	} else {
-		nd->flags &= ~LOOKUP_RCU;
-		if (!(nd->flags & LOOKUP_ROOT))
-			nd->root.mnt = NULL;
-		rcu_read_unlock();
-	}
-}
-
 /*
  * Do we need to follow links? We _really_ want to be able
  * to do this check without having to look at inode->i_op,
@@ -1622,8 +1622,8 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd)
 	int res;
 
 	if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
-		path_put_conditional(path, nd);
-		path_put(&nd->path);
+		path_to_nameidata(path, nd);
+		terminate_walk(nd);
 		return -ELOOP;
 	}
 	BUG_ON(nd->depth >= MAX_NESTED_LINKS);
@@ -3238,8 +3238,8 @@ static struct file *path_openat(int dfd, struct filename *pathname,
 		struct path link = path;
 		void *cookie;
 		if (!(nd->flags & LOOKUP_FOLLOW)) {
-			path_put_conditional(&path, nd);
-			path_put(&nd->path);
+			path_to_nameidata(&path, nd);
+			terminate_walk(nd);
 			error = -ELOOP;
 			break;
 		}


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