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Date: Wed, 4 Nov 2015 11:16:24 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Michael Kerrisk <mtk.manpages@gmail.com>,
        linux-api@vger.kernel.org, Hugh Dickins <hughd@google.com>,
        Johannes Weiner <hannes@cmpxchg.org>, Rik van Riel <riel@redhat.com>,
        Mel Gorman <mgorman@suse.de>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Jason Evans <je@fb.com>, Daniel Micay <danielmicay@gmail.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Shaohua Li <shli@kernel.org>, Michal Hocko <mhocko@suse.cz>,
        yalin.wang2010@gmail.com,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [PATCH v2 01/13] mm: support madvise(MADV_FREE)
Message-ID: <20151104021624.GA2476@swordfish>
References: <1446600367-7976-1-git-send-email-minchan@kernel.org>
 <1446600367-7976-2-git-send-email-minchan@kernel.org>
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Hi Minchan,

On (11/04/15 10:25), Minchan Kim wrote:
[..]
>+static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
>+                               unsigned long end, struct mm_walk *walk)
>+
...
> +	if (pmd_trans_unstable(pmd))
> +		return 0;

I think it makes sense to update pmd_trans_unstable() and
pmd_none_or_trans_huge_or_clear_bad() comments in asm-generic/pgtable.h
Because they explicitly mention MADV_DONTNEED only. Just a thought.


> @@ -379,6 +502,14 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
>  		return madvise_remove(vma, prev, start, end);
>  	case MADV_WILLNEED:
>  		return madvise_willneed(vma, prev, start, end);
> +	case MADV_FREE:
> +		/*
> +		 * XXX: In this implementation, MADV_FREE works like
		  ^^^^
		XXX

> +		 * MADV_DONTNEED on swapless system or full swap.
> +		 */
> +		if (get_nr_swap_pages() > 0)
> +			return madvise_free(vma, prev, start, end);
> +		/* passthrough */

	-ss