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Subject: Re: [PATCH] mm: filemap: correct the comment about VM_FAULT_RETRY
To:     josef@toxicpanda.com, akpm@linux-foundation.org
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org
References: <1556234531-108228-1-git-send-email-yang.shi@linux.alibaba.com>
From:   Yang Shi <yang.shi@linux.alibaba.com>
Message-ID: <66e2f965-4f4d-a755-69b3-5342aa761ff3@linux.alibaba.com>
Date:   Wed, 8 May 2019 09:55:21 -0700
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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@toxicpanda.com>
> Signed-off-by: Yang Shi <yang.shi@linux.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.