Re: [PATCH] ovl: skip stale entries in merge dir cache iteration

[Amir Goldstein <amir73il@gmail.com>]

On Mon, Apr 26, 2021 at 6:20 PM Amir Goldstein <amir73il@gmail.com> wrote:
>
> On the first getdents call, ovl_iterate() populates the readdir cache
> with a list of entries, but for upper entries with origin lower inode,
> p->ino remains zero.
>
> Following getdents calls traverse the readdir cache list and call
> ovl_cache_update_ino() for entries with zero p->ino to lookup the entry
> in the overlay and return d_ino that is consistent with st_ino.
>
> If the upper file was unlinked between the first getdents call and the
> getdents call that lists the file entry, ovl_cache_update_ino() will not
> find the entry and fall back to setting d_ino to the upper real st_ino,
> which is inconsistent with how this object was presented to users.
>
> Instead of listing a stale entry with inconsistent d_ino, simply skip
> the stale entry, which is better for users.
>

Miklos,

I forgot to follow up on this patch.
Upstream xfstest overlay/077 is failing without this patch.
Please add:
Link: https://lore.kernel.org/fstests/CAOQ4uxgR_cLnC_vdU5=seP3fwqVkuZM_-WfD6maFTMbMYq=a9w@mail.gmail.com/

Thanks,
Amir.


> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  fs/overlayfs/readdir.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
> index cc1e80257064..10b7780e4bdc 100644
> --- a/fs/overlayfs/readdir.c
> +++ b/fs/overlayfs/readdir.c
> @@ -481,6 +481,8 @@ static int ovl_cache_update_ino(struct path *path, struct ovl_cache_entry *p)
>         }
>         this = lookup_one_len(p->name, dir, p->len);
>         if (IS_ERR_OR_NULL(this) || !this->d_inode) {
> +               /* Mark a stale entry */
> +               p->is_whiteout = true;
>                 if (IS_ERR(this)) {
>                         err = PTR_ERR(this);
>                         this = NULL;
> @@ -776,6 +778,9 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx)
>                                 if (err)
>                                         goto out;
>                         }
> +               }
> +               /* ovl_cache_update_ino() sets is_whiteout on stale entry */
> +               if (!p->is_whiteout) {
>                         if (!dir_emit(ctx, p->name, p->len, p->ino, p->type))
>                                 break;
>                 }
> --
> 2.25.1
>