linux-kernel - Re: [PATCH] mm/madvise: fix madvise_pageout for private file mappings

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Date:   Thu, 1 Dec 2022 19:06:37 +0530
From:   Pavan Kondeti <quic_pkondeti@...cinc.com>
To:     David Hildenbrand <david@...hat.com>
CC:     Pavankumar Kondeti <quic_pkondeti@...cinc.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Minchan Kim <minchan@...nel.org>,
        Charan Teja Kalla <quic_charante@...cinc.com>,
        Prakash Gupta <quic_guptap@...cinc.com>,
        Divyanand Rangu <quic_drangu@...cinc.com>
Subject: Re: [PATCH] mm/madvise: fix madvise_pageout for private file mappings

Hi David,

Thanks for your review.

On Thu, Dec 01, 2022 at 02:01:22PM +0100, David Hildenbrand wrote:
> >+	 * If the VMA belongs to a private file mapping, there can be private
> >+	 * dirty pages which can be paged out if even this process is neither
> >+	 * owner nor write capable of the file. Cache the file access check
> >+	 * here and use it later during page walk.
> >+	 */
> >+	can_pageout_file = can_do_file_pageout(vma);
> 
> Why not move that into madvise_pageout_page_range() ? Avoids passing this
> variable to that function.
> 
Silly me. I should have done that in the first place.

> In fact, why not even call that function directly instead of storing that in
> madvise_walk_private(). The function is extremely lightweight.

Agreed. I will incorporate your suggestion and send the patch after testing.

> 
> >  	lru_add_drain();
> >  	tlb_gather_mmu(&tlb, mm);
> >-	madvise_pageout_page_range(&tlb, vma, start_addr, end_addr);
> >+	madvise_pageout_page_range(&tlb, vma, start_addr, end_addr, can_pageout_file);
> >  	tlb_finish_mmu(&tlb);
> >  	return 0;
> 
Thanks,
Pavan