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Subject: Re: [PATCH] mm: madvise: MADV_DONTNEED_LOCKED
From:   Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <20220303212956.229409-1-hannes@cmpxchg.org>
Date:   Thu, 3 Mar 2022 13:35:56 -0800
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Linux-MM <linux-mm@kvack.org>, linux-kernel@vger.kernel.org
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Message-Id: <A5A8E655-0CE6-4F27-85FD-E99726776EAC@gmail.com>
References: <20220303212956.229409-1-hannes@cmpxchg.org>
To:     Johannes Weiner <hannes@cmpxchg.org>
Precedence: bulk


> On Mar 3, 2022, at 1:29 PM, Johannes Weiner <hannes@cmpxchg.org> =
wrote:
>=20
> MADV_DONTNEED historically rejects mlocked ranges, but with
> MLOCK_ONFAULT and MCL_ONFAULT allowing to mlock without populating,
> there are valid use cases for depopulating locked ranges as well.

...

> @@ -850,7 +858,7 @@ static long madvise_dontneed_free(struct =
vm_area_struct *vma,
> 		VM_WARN_ON(start >=3D end);
> 	}
>=20
> -	if (behavior =3D=3D MADV_DONTNEED)
> +	if (behavior =3D=3D MADV_DONTNEED || behavior =3D=3D =
MADV_DONTNEED_LOCKED)
> 		return madvise_dontneed_single_vma(vma, start, end);
> 	else if (behavior =3D=3D MADV_FREE)
> 		return madvise_free_single_vma(vma, start, end);
> @@ -988,6 +996,7 @@ static int madvise_vma_behavior(struct =
vm_area_struct *vma,
> 		return madvise_pageout(vma, prev, start, end);
> 	case MADV_FREE:
> 	case MADV_DONTNEED:
> +	case MADV_DONTNEED_LOCKED:
> 		return madvise_dontneed_free(vma, prev, start, end, =
behavior);
> 	case MADV_POPULATE_READ:
> 	case MADV_POPULATE_WRITE:
> @@ -1113,6 +1122,7 @@ madvise_behavior_valid(int behavior)
> 	case MADV_REMOVE:
> 	case MADV_WILLNEED:
> 	case MADV_DONTNEED:
> +	case MADV_DONTNEED_LOCKED:
> 	case MADV_FREE:
> 	case MADV_COLD:
> 	case MADV_PAGEOUT:

Don=E2=80=99t you want to change madvise_need_mmap_write() as well and =
add
MADV_DONTNEED_LOCKED there too?