linux-kernel - [PATCH 20/24] namei: introduce nameidata->stack

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Message-Id: <1429553588-24764-20-git-send-email-viro@ZenIV.linux.org.uk>
Date:	Mon, 20 Apr 2015 19:13:04 +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 20/24] namei: introduce nameidata->stack

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

move the stack of saved states out of link_path_walk() stack frame to
that of callers, put a reference to it into struct nameidata as
nd->stack, move nd->saved_names[] elements in there.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/namei.c | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index e03c18f..1c967d1 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -504,7 +504,12 @@ struct nameidata {
 	int		link_count,
 			total_link_count;
 	struct file	*base;
-	char *saved_names[MAX_NESTED_LINKS + 1];
+	struct saved {
+		struct path link;
+		const char *name;
+		void *cookie;
+		char *body;
+	} *stack;
 };
 
 static struct nameidata *set_nameidata(struct nameidata *p)
@@ -738,13 +743,13 @@ void nd_set_link(char *path)
 {
 	struct nameidata *nd = current->nameidata;
 
-	nd->saved_names[nd->depth] = path;
+	nd->stack[nd->depth].body = path;
 }
 EXPORT_SYMBOL(nd_set_link);
 
 static inline char *nd_get_link(struct nameidata *nd)
 {
-	return nd->saved_names[nd->depth];
+	return nd->stack[nd->depth].body;
 }
 
 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
@@ -1770,11 +1775,7 @@ static inline u64 hash_name(const char *name)
  */
 static int link_path_walk(const char *name, struct nameidata *nd)
 {
-	struct saved {
-		struct path link;
-		void *cookie;
-		const char *name;
-	} stack[MAX_NESTED_LINKS], *last = stack + nd->depth - 1;
+	struct saved *last = nd->stack;
 	struct path next;
 	int err;
 
@@ -2092,7 +2093,11 @@ static int filename_lookup(int dfd, struct filename *name,
 				unsigned int flags, struct nameidata *nd)
 {
 	int retval;
-	struct nameidata *saved_nd = set_nameidata(nd);
+	struct saved stack[MAX_NESTED_LINKS + 1];
+	struct nameidata *saved_nd;
+
+	nd->stack = stack;
+	saved_nd = set_nameidata(nd);
 
 	retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
 	if (unlikely(retval == -ECHILD))
@@ -2409,9 +2414,12 @@ static int
 path_mountpoint(int dfd, const struct filename *name, struct path *path,
 		unsigned int flags)
 {
-	struct nameidata nd, *saved = set_nameidata(&nd);
+	struct saved stack[MAX_NESTED_LINKS + 1];
+	struct nameidata nd, *saved;
 	int err;
 
+	nd.stack = stack;
+	saved = set_nameidata(&nd);
 	err = path_init(dfd, name, flags, &nd);
 	if (unlikely(err))
 		goto out;
@@ -3280,6 +3288,7 @@ static struct file *path_openat(int dfd, struct filename *pathname,
 	struct path path;
 	int opened = 0;
 	int error;
+	struct saved stack[MAX_NESTED_LINKS + 1];
 	struct nameidata *saved_nd;
 
 	file = get_empty_filp();
@@ -3287,6 +3296,7 @@ static struct file *path_openat(int dfd, struct filename *pathname,
 		return file;
 
 	file->f_flags = op->open_flag;
+	nd->stack = stack;
 	saved_nd = set_nameidata(nd);
 
 	if (unlikely(file->f_flags & __O_TMPFILE)) {
@@ -4491,11 +4501,14 @@ EXPORT_SYMBOL(readlink_copy);
  */
 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 {
-	struct nameidata nd, *saved = set_nameidata(&nd);
+	struct saved stack;
+	struct nameidata nd, *saved;
 	void *cookie;
 	int res;
 
 	nd.depth = 0;
+	nd.stack = &stack;
+	saved = set_nameidata(&nd);
 	cookie = dentry->d_inode->i_op->follow_link(dentry);
 	if (IS_ERR(cookie))
 		res = PTR_ERR(cookie);
-- 
2.1.4

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