Re: [RFC] fuse: consistently use readdirplus offsets

[Miklos Szeredi <miklos-sUDqSbJrdHQHWmgEVkV9KA@public.gmane.org>]

On Tue, Feb 5, 2013 at 4:12 AM, Eric Wong <normalperson-rMlxZR9MS24@public.gmane.org> wrote:
> Miklos Szeredi <miklos-sUDqSbJrdHQHWmgEVkV9KA@public.gmane.org> wrote:
>> I think the problem is that directory offsets are not consistent
>> between readdir and readdirplus.  The solution is that userspace
>> should always use the same offsets.  This makes the readdirplus
>> implementation more complex but that's really the only sane thing to
>> do.
>
> I think something like the following is necessary in the kernel, too.
> (Userspace patch coming)

Can you please explain what this patch is trying to do?  Because I
think it's not doing what it wants ;)

Thanks,
Miklos

>
> ------------------------------- 8< --------------------------------
> From ed52619fda61c8f2b723ef72666e7acdd8885a1c Mon Sep 17 00:00:00 2001
> From: Eric Wong <normalperson-rMlxZR9MS24@public.gmane.org>
> Date: Tue, 5 Feb 2013 02:54:28 +0000
> Subject: [PATCH] fuse: consistently use readdirplus offsets
>
> With adaptive readdirplus, filesystems may switch between normal
> readdir or readdirplus requests.  However, directory offsets
> must be maintained consistently to prevent the kernel from
> misinterpreting the offsets between different requests which
> may use the same buffer.
>
> Signed-off-by: Eric Wong <normalperson-rMlxZR9MS24@public.gmane.org>
> ---
>  fs/fuse/dir.c |    7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
> index dc5e648..a8e4abb 100644
> --- a/fs/fuse/dir.c
> +++ b/fs/fuse/dir.c
> @@ -1313,7 +1313,7 @@ static int parse_dirplusfile(char *buf, size_t nbytes, struct file *file,
>
>  static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir)
>  {
> -       int plus, err;
> +       int err;
>         size_t nbytes;
>         struct page *page;
>         struct inode *inode = file->f_path.dentry->d_inode;
> @@ -1334,12 +1334,11 @@ static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir)
>                 return -ENOMEM;
>         }
>
> -       plus = fuse_use_readdirplus(inode, file);
>         req->out.argpages = 1;
>         req->num_pages = 1;
>         req->pages[0] = page;
>         req->page_descs[0].length = PAGE_SIZE;
> -       if (plus) {
> +       if (fuse_use_readdirplus(inode, file)) {
>                 attr_version = fuse_get_attr_version(fc);
>                 fuse_read_fill(req, file, file->f_pos, PAGE_SIZE,
>                                FUSE_READDIRPLUS);
> @@ -1352,7 +1351,7 @@ static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir)
>         err = req->out.h.error;
>         fuse_put_request(fc, req);
>         if (!err) {
> -               if (plus) {
> +               if (fc->do_readdirplus) {
>                         err = parse_dirplusfile(page_address(page), nbytes,
>                                                 file, dstbuf, filldir,
>                                                 attr_version);
> --
> Eric Wong

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