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From: Miklos Szeredi <miklos@szeredi.hu>
To: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] fuse: Replace page without copying in fuse_writepage_in_flight()
Date: Tue, 15 Jan 2019 16:39:39 +0100	[thread overview]
Message-ID: <CAJfpegvKxJ06hfXR5yxWkdz0GzTw7vR2x8E5bjdO1df1J1C54w@mail.gmail.com> (raw)
In-Reply-To: <154322557765.18737.14337090699283695815.stgit@localhost.localdomain>

On Mon, Nov 26, 2018 at 10:46 AM Kirill Tkhai <ktkhai@virtuozzo.com> wrote:
>
> It looks like we can optimize old_req page replacement
> and avoid copying by simple updating the request's page.
>
> Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> ---
>  fs/fuse/file.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index c6650c68b31a..83b54b082c86 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1778,7 +1778,7 @@ static bool fuse_writepage_in_flight(struct fuse_req *new_req,
>         if (old_req->num_pages == 1 && old_req != first_req) {
>                 struct backing_dev_info *bdi = inode_to_bdi(page->mapping->host);
>
> -               copy_highpage(old_req->pages[0], page);
> +               swap(old_req->pages[0], page);

This would mess up refcounting for all pages involved.   need to swap
with the temp page in new_req.    Fixed version in #for-next.

Thanks,
Miklos

  reply	other threads:[~2019-01-15 15:39 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-26  9:46 [PATCH 1/2] fuse: Fix race in fuse_writepage_in_flight() Kirill Tkhai
2018-11-26  9:46 ` [PATCH 2/2] fuse: Replace page without copying " Kirill Tkhai
2019-01-15 15:39   ` Miklos Szeredi [this message]
2019-01-15 16:14     ` Kirill Tkhai
2019-01-15 16:36       ` Miklos Szeredi
2019-01-15 16:38         ` Kirill Tkhai
2019-01-10 10:48 ` [PATCH 1/2] fuse: Fix race " Kirill Tkhai
2019-01-10 11:00   ` Miklos Szeredi
2019-01-10 11:03     ` Kirill Tkhai
2019-01-15 15:37       ` Miklos Szeredi
2019-01-15 15:55         ` Kirill Tkhai
2019-01-15 16:03           ` Miklos Szeredi
2019-01-15 16:05             ` Kirill Tkhai

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