linux-kernel - Re: [PATCH] mm: filemap: correct the comment about VM_FAULT

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Message-ID: <CAPhsuW5B5twTEk=SZZqZCH9_hjEjJ_KFP_GYq3T6nzv7kRSM0w@mail.gmail.com>
Date:   Tue, 14 May 2019 16:40:12 -0700
From:   Song Liu <liu.song.a23@...il.com>
To:     Yang Shi <yang.shi@...ux.alibaba.com>, jbacik@...com
Cc:     josef@...icpanda.com, Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: filemap: correct the comment about VM_FAULT_RETRY

On Thu, Apr 25, 2019 at 4:22 PM Yang Shi <yang.shi@...ux.alibaba.com> wrote:
>
> The commit 6b4c9f446981 ("filemap: drop the mmap_sem for all blocking
> operations") changed when mmap_sem is dropped during filemap page fault
> and when returning VM_FAULT_RETRY.
>
> Correct the comment to reflect the change.
>
> Cc: Josef Bacik <josef@...icpanda.com>
> Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>

Looks good to me!

Acked-by: Song Liu <songliubraving@...com>

> ---
>  mm/filemap.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index d78f577..f0d6250 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2545,10 +2545,8 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
>   *
>   * vma->vm_mm->mmap_sem must be held on entry.
>   *
> - * If our return value has VM_FAULT_RETRY set, it's because
> - * lock_page_or_retry() returned 0.
> - * The mmap_sem has usually been released in this case.
> - * See __lock_page_or_retry() for the exception.
> + * If our return value has VM_FAULT_RETRY set, it's because the mmap_sem
> + * may be dropped before doing I/O or by lock_page_maybe_drop_mmap().
>   *
>   * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
>   * has not been released.
> --
> 1.8.3.1
>