From: Kirill Tkhai <ktkhai@virtuozzo.com>
To: Miklos Szeredi <miklos@szeredi.hu>
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 19:14:39 +0300 [thread overview]
Message-ID: <30c6d750-01b1-fb7e-eb80-0f60f242974a@virtuozzo.com> (raw)
In-Reply-To: <CAJfpegvKxJ06hfXR5yxWkdz0GzTw7vR2x8E5bjdO1df1J1C54w@mail.gmail.com>
On 15.01.2019 18:39, Miklos Szeredi wrote:
> 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.
You are sure, page is just a simple pointer, not struct **page.
Then we would have had to change fuse_writepage_in_flight() to use ** pointer.
Updated version looks good for me.
Thanks,
Kirill
next prev parent reply other threads:[~2019-01-15 16:14 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
2019-01-15 16:14 ` Kirill Tkhai [this message]
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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