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

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Date:   Tue, 14 May 2019 15:50:07 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     josef@...icpanda.com, Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: filemap: correct the comment about VM_FAULT_RETRY

Hi Josef,

Any comment on this patch? I switched to my personal email since the
mail may get bounced back with my work email sometime.


On Wed, May 8, 2019 at 9:55 AM Yang Shi <yang.shi@...ux.alibaba.com> wrote:
>
> Ping.
>
>
> Josef, any comment on this one?
>
>
> Thanks,
>
> Yang
>
>
>
> On 4/25/19 4:22 PM, Yang Shi 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>
> > ---
> >   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.
>