[47/79] namei: move link/cookie pairs into nameidata
diff mbox

Message ID 1430803373-4948-47-git-send-email-viro@ZenIV.linux.org.uk
State New
Headers show

Commit Message

Al Viro May 5, 2015, 5:22 a.m. UTC
From: Al Viro <viro@zeniv.linux.org.uk>

Array of MAX_NESTED_LINKS + 1 elements put into nameidata;
what used to be a local array in link_path_walk() occupies
entries 1 .. MAX_NESTED_LINKS in it, link and cookie from
the trailing symlink handling loops - entry 0.

This is _not_ the final arrangement; just an easily verified
incremental step.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/namei.c | 35 ++++++++++++++++++-----------------
 1 file changed, 18 insertions(+), 17 deletions(-)

Comments

NeilBrown May 6, 2015, 2:42 a.m. UTC | #1
On Tue,  5 May 2015 06:22:21 +0100 Al Viro <viro@ZenIV.linux.org.uk> wrote:

> From: Al Viro <viro@zeniv.linux.org.uk>
> 
> Array of MAX_NESTED_LINKS + 1 elements put into nameidata;
> what used to be a local array in link_path_walk() occupies
> entries 1 .. MAX_NESTED_LINKS in it, link and cookie from
> the trailing symlink handling loops - entry 0.
> 
> This is _not_ the final arrangement; just an easily verified
> incremental step.
> 
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
>  fs/namei.c | 35 ++++++++++++++++++-----------------
>  1 file changed, 18 insertions(+), 17 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 38ff968..e6d54ec 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -505,6 +505,11 @@ struct nameidata {
>  	int		last_type;
>  	unsigned	depth;
>  	struct file	*base;
> +	struct saved {
> +		struct path link;
> +		void *cookie;
> +		const char *name;
> +	} stack[MAX_NESTED_LINKS + 1];
>  };
>  
>  /*
> @@ -1703,11 +1708,7 @@ 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;

This looks wrong.  'last'  used to be dependent on nd->depth, now it isn't.

Three patches later we have:

+const char *get_link(struct nameidata *nd)
 {
-	struct dentry *dentry = link->dentry;
+	struct saved *last = nd->stack + nd->depth;
+	struct dentry *dentry = nd->link.dentry;
 	struct inode *inode = dentry->d_inode;

and 

 static int link_path_walk(const char *name, struct nameidata *nd)
 {
-	struct saved *last = nd->stack;
 	int err;

....
-			last->link = nd->link;
-			s = get_link(&last->link, nd, &last->cookie);
+			s = get_link(nd);


so the nd->depth offset is restored in get_link() so the next result appears
correct, but the intermediate states appear to be wrong.

NeilBrown
Al Viro May 6, 2015, 7:22 a.m. UTC | #2
On Wed, May 06, 2015 at 12:42:54PM +1000, NeilBrown wrote:
> >  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;
> 
> This looks wrong.  'last'  used to be dependent on nd->depth, now it isn't.

On the entry to link_path_walk() we have nd->depth == 0.

And nd->depth and last are changed in sync.
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch
diff mbox

diff --git a/fs/namei.c b/fs/namei.c
index 38ff968..e6d54ec 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -505,6 +505,11 @@  struct nameidata {
 	int		last_type;
 	unsigned	depth;
 	struct file	*base;
+	struct saved {
+		struct path link;
+		void *cookie;
+		const char *name;
+	} stack[MAX_NESTED_LINKS + 1];
 };
 
 /*
@@ -1703,11 +1708,7 @@  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;
 	int err;
 
 	while (*name=='/')
@@ -2022,13 +2023,13 @@  static int path_lookupat(int dfd, const struct filename *name,
 	if (!err && !(flags & LOOKUP_PARENT)) {
 		err = lookup_last(nd);
 		while (err > 0) {
-			void *cookie;
-			struct path link = nd->link;
-			err = trailing_symlink(&link, nd, &cookie);
+			nd->stack[0].link = nd->link;
+			err = trailing_symlink(&nd->stack[0].link,
+						nd, &nd->stack[0].cookie);
 			if (err)
 				break;
 			err = lookup_last(nd);
-			put_link(nd, &link, cookie);
+			put_link(nd, &nd->stack[0].link, nd->stack[0].cookie);
 		}
 	}
 
@@ -2368,13 +2369,13 @@  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 = trailing_symlink(&link, nd, &cookie);
+		nd->stack[0].link = nd->link;
+		err = trailing_symlink(&nd->stack[0].link,
+					nd, &nd->stack[0].cookie);
 		if (err)
 			break;
 		err = mountpoint_last(nd, path);
-		put_link(nd, &link, cookie);
+		put_link(nd, &nd->stack[0].link, nd->stack[0].cookie);
 	}
 out:
 	path_cleanup(nd);
@@ -3253,14 +3254,14 @@  static struct file *path_openat(int dfd, struct filename *pathname,
 
 	error = do_last(nd, file, op, &opened, pathname);
 	while (unlikely(error > 0)) { /* trailing symlink */
-		struct path link = nd->link;
-		void *cookie;
 		nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
-		error = trailing_symlink(&link, nd, &cookie);
+		nd->stack[0].link = nd->link;
+		error= trailing_symlink(&nd->stack[0].link,
+					nd, &nd->stack[0].cookie);
 		if (unlikely(error))
 			break;
 		error = do_last(nd, file, op, &opened, pathname);
-		put_link(nd, &link, cookie);
+		put_link(nd, &nd->stack[0].link, nd->stack[0].cookie);
 	}
 out:
 	path_cleanup(nd);