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SubjectRe: [PATCH 47/79] namei: move link/cookie pairs into nameidata
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

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