linux-kernel - Re: [PATCH 08/10] orangefs: use attach/detach_page

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Date:   Tue, 26 May 2020 17:54:04 -0400
From:   Mike Marshall <hubcap@...ibond.com>
To:     Guoqing Jiang <guoqing.jiang@...ud.ionos.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dave Chinner <david@...morbit.com>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Martin Brandenburg <martin@...ibond.com>,
        devel@...ts.orangefs.org
Subject: Re: [PATCH 08/10] orangefs: use attach/detach_page_private

I apologize for not mentioning that I ran this patch set
through orangefs xfstests at 5.7 rc5 with no problems
or regressions.

-Mike


On Sun, May 17, 2020 at 5:47 PM Guoqing Jiang
<guoqing.jiang@...ud.ionos.com> wrote:
>
> Since the new pair function is introduced, we can call them to clean the
> code in orangefs.
>
> Cc: Mike Marshall <hubcap@...ibond.com>
> Cc: Martin Brandenburg <martin@...ibond.com>
> Cc: devel@...ts.orangefs.org
> Signed-off-by: Guoqing Jiang <guoqing.jiang@...ud.ionos.com>
> ---
> No change since RFC V3.
>
> RFC V2 -> RFC V3
> 1. rename clear_page_private to detach_page_private.
>
> RFC -> RFC V2
> 1. change the name of new functions to attach/clear_page_private.
> 2. avoid potential use-after-free as suggested by Dave Chinner.
>
>  fs/orangefs/inode.c | 32 ++++++--------------------------
>  1 file changed, 6 insertions(+), 26 deletions(-)
>
> diff --git a/fs/orangefs/inode.c b/fs/orangefs/inode.c
> index 12ae630fbed7..48f0547d4850 100644
> --- a/fs/orangefs/inode.c
> +++ b/fs/orangefs/inode.c
> @@ -62,12 +62,7 @@ static int orangefs_writepage_locked(struct page *page,
>         } else {
>                 ret = 0;
>         }
> -       if (wr) {
> -               kfree(wr);
> -               set_page_private(page, 0);
> -               ClearPagePrivate(page);
> -               put_page(page);
> -       }
> +       kfree(detach_page_private(page));
>         return ret;
>  }
>
> @@ -409,9 +404,7 @@ static int orangefs_write_begin(struct file *file,
>         wr->len = len;
>         wr->uid = current_fsuid();
>         wr->gid = current_fsgid();
> -       SetPagePrivate(page);
> -       set_page_private(page, (unsigned long)wr);
> -       get_page(page);
> +       attach_page_private(page, wr);
>  okay:
>         return 0;
>  }
> @@ -459,18 +452,12 @@ static void orangefs_invalidatepage(struct page *page,
>         wr = (struct orangefs_write_range *)page_private(page);
>
>         if (offset == 0 && length == PAGE_SIZE) {
> -               kfree((struct orangefs_write_range *)page_private(page));
> -               set_page_private(page, 0);
> -               ClearPagePrivate(page);
> -               put_page(page);
> +               kfree(detach_page_private(page));
>                 return;
>         /* write range entirely within invalidate range (or equal) */
>         } else if (page_offset(page) + offset <= wr->pos &&
>             wr->pos + wr->len <= page_offset(page) + offset + length) {
> -               kfree((struct orangefs_write_range *)page_private(page));
> -               set_page_private(page, 0);
> -               ClearPagePrivate(page);
> -               put_page(page);
> +               kfree(detach_page_private(page));
>                 /* XXX is this right? only caller in fs */
>                 cancel_dirty_page(page);
>                 return;
> @@ -535,12 +522,7 @@ static int orangefs_releasepage(struct page *page, gfp_t foo)
>
>  static void orangefs_freepage(struct page *page)
>  {
> -       if (PagePrivate(page)) {
> -               kfree((struct orangefs_write_range *)page_private(page));
> -               set_page_private(page, 0);
> -               ClearPagePrivate(page);
> -               put_page(page);
> -       }
> +       kfree(detach_page_private(page));
>  }
>
>  static int orangefs_launder_page(struct page *page)
> @@ -740,9 +722,7 @@ vm_fault_t orangefs_page_mkwrite(struct vm_fault *vmf)
>         wr->len = PAGE_SIZE;
>         wr->uid = current_fsuid();
>         wr->gid = current_fsgid();
> -       SetPagePrivate(page);
> -       set_page_private(page, (unsigned long)wr);
> -       get_page(page);
> +       attach_page_private(page, wr);
>  okay:
>
>         file_update_time(vmf->vma->vm_file);
> --
> 2.17.1
>