From: Andrew Morton <akpm@linux-foundation.org>
To: Chen Wandun <chenwandun@huawei.com>
Cc: <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
<wangkefeng.wang@huawei.com>
Subject: Re: [PATCH] mm: avoid unnecessary page table walk for __get_user_pages
Date: Wed, 7 Sep 2022 16:34:08 -0700 [thread overview]
Message-ID: <20220907163408.f9a9152314d33afc74cb1f0c@linux-foundation.org> (raw)
In-Reply-To: <20220906024401.133336-1-chenwandun@huawei.com>
On Tue, 6 Sep 2022 10:44:01 +0800 Chen Wandun <chenwandun@huawei.com> wrote:
> It is no need to walk page table and find pages if faultin_page success
> and __get_user_pages does't care pages at all, so directly handle next
> page.
>
> ...
>
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1198,7 +1198,10 @@ static long __get_user_pages(struct mm_struct *mm,
> PTR_ERR(page) == -EMLINK, locked);
> switch (ret) {
> case 0:
> - goto retry;
> + if (pages)
> + goto retry;
> + else
> + goto next_page;
> case -EBUSY:
> case -EAGAIN:
> ret = 0;
Looks right to me. I redid the changelog somewhat:
: There is no need to walk page tables and find pages if faultin_page)_
: succeeds and __get_user_pages)_ doesn't care about populating the pages[]
: array. So directly go on to handle the next page.
next prev parent reply other threads:[~2022-09-07 23:34 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-06 2:44 Chen Wandun
2022-09-07 23:34 ` Andrew Morton [this message]
2022-09-08 1:58 ` John Hubbard
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