linux-kernel - Re: [v4 PATCH 2/2] mm: swap: add comment for swap_vma

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Date:   Thu, 03 Jan 2019 15:41:05 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     <tim.c.chen@...el.com>, <minchan@...nel.org>,
        <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [v4 PATCH 2/2] mm: swap: add comment for swap_vma_readahead

Yang Shi <yang.shi@...ux.alibaba.com> writes:

> swap_vma_readahead()'s comment is missed, just add it.
>
> Cc: Huang Ying <ying.huang@...el.com>
> Cc: Tim Chen <tim.c.chen@...el.com>
> Cc: Minchan Kim <minchan@...nel.org>
> Signed-off-by: Yang Shi <yang.shi@...ux.alibaba.com>
> ---
>  mm/swap_state.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 78d500e..dd8f698 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -698,6 +698,23 @@ static void swap_ra_info(struct vm_fault *vmf,
>  	pte_unmap(orig_pte);
>  }
>  
> +/**
> + * swap_vm_readahead - swap in pages in hope we need them soon

s/swap_vm_readahead/swap_vma_readahead/

> + * @entry: swap entry of this memory
> + * @gfp_mask: memory allocation flags
> + * @vmf: fault information
> + *
> + * Returns the struct page for entry and addr, after queueing swapin.
> + *
> + * Primitive swap readahead code. We simply read in a few pages whoes
> + * virtual addresses are around the fault address in the same vma.
> + *
> + * This has been extended to use the NUMA policies from the mm triggering
> + * the readahead.

What is this?  I know you copy it from swap_cluster_readahead(), but we
have only one mm for vma readahead.

> + * Caller must hold down_read on the vma->vm_mm if vmf->vma is not NULL.

Better to make it explicit that your are talking about mmap_sem?

Best Regards,
Huang, Ying

> + *
> + */
>  static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
>  				       struct vm_fault *vmf)
>  {