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From: Peter Xu <peterx@redhat.com>
To: Brian Geffon <bgeffon@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Axel Rasmussen <axelrasmussen@google.com>,
	Lokesh Gidra <lokeshgidra@google.com>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Hugh Dickins <hughd@google.com>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Vlastimil Babka <vbabka@suse.cz>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Sonny Rao <sonnyrao@google.com>, Minchan Kim <minchan@kernel.org>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	Dmitry Safonov <dima@arista.com>
Subject: Re: [PATCH v2 1/2] mm: Allow non-VM_DONTEXPAND and VM_PFNMAP mappings with MREMAP_DONTUNMAP
Date: Wed, 17 Mar 2021 17:18:57 -0400	[thread overview]
Message-ID: <20210317211857.GN395976@xz-x1> (raw)
In-Reply-To: <CADyq12z6vQ0qHs14aVOFgqfn9pvFak-vwEVmLTObMQ1exsOM+g@mail.gmail.com>

On Wed, Mar 17, 2021 at 04:44:25PM -0400, Brian Geffon wrote:
> Hi Peter,

Hi, Brian,

> Thank you as always for taking a look. This change relies on the
> existing check in vma_to_resize on line 686:
> https://elixir.bootlin.com/linux/v5.12-rc3/source/mm/mremap.c#L686
> which returns -EFAULT when the vma is VM_DONTEXPAND or VM_PFNMAP.

Do you mean line 676?

https://elixir.bootlin.com/linux/v5.12-rc3/source/mm/mremap.c#L676

I'm not sure whether it'll work for MREMAP_DONTUNMAP, since IIUC
MREMAP_DONTUNMAP only works for the remap case with no size change, however in
that case in vma_to_resize() we'll bail out even earlier than line 676 when
checking against the size:

https://elixir.bootlin.com/linux/v5.12-rc3/source/mm/mremap.c#L667

So IIUC we'll still need the change as Hugh suggested previously.

Thanks,

-- 
Peter Xu



  reply	other threads:[~2021-03-17 21:19 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-03 17:52 [PATCH] mm: Allow shmem " Brian Geffon
2021-03-03 18:13 ` Brian Geffon
2021-03-03 19:04   ` Lokesh Gidra
2021-03-14  4:19 ` Hugh Dickins
2021-03-16 19:18   ` Brian Geffon
2021-03-16 19:31     ` Dmitry Safonov
2021-03-16 20:17   ` Peter Xu
2021-03-19  1:58     ` Hugh Dickins
2021-03-17 19:13 ` [PATCH v2 1/2] mm: Allow non-VM_DONTEXPAND and VM_PFNMAP " Brian Geffon
2021-03-17 19:13   ` [PATCH v2 2/2] Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio" Brian Geffon
2021-03-17 20:40   ` [PATCH v2 1/2] mm: Allow non-VM_DONTEXPAND and VM_PFNMAP mappings with MREMAP_DONTUNMAP Peter Xu
2021-03-17 20:44     ` Brian Geffon
2021-03-17 21:18       ` Peter Xu [this message]
2021-03-17 21:25         ` Brian Geffon
2021-03-17 21:41 ` [PATCH v3 " Brian Geffon
2021-03-17 21:41   ` [PATCH v3 2/2] Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio" Brian Geffon
2021-03-19  1:28     ` Hugh Dickins
2021-03-17 22:03   ` [PATCH v3 1/2] mm: Allow non-VM_DONTEXPAND and VM_PFNMAP mappings with MREMAP_DONTUNMAP Andrew Morton
2021-03-19  1:20   ` Hugh Dickins
2021-03-23 16:26 ` [PATCH v4 1/3] mm: Extend MREMAP_DONTUNMAP to non-anonymous mappings Brian Geffon
2021-03-23 16:26   ` [PATCH v4 2/3] Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio" Brian Geffon
2021-03-23 18:16     ` Hugh Dickins
2021-03-23 18:26       ` Brian Geffon
2021-03-23 16:26   ` [PATCH v4 3/3] selftests: Add a MREMAP_DONTUNMAP selftest for shmem Brian Geffon
2021-03-23 16:26   ` [PATCH] mremap.2: MREMAP_DONTUNMAP to reflect to supported mappings Brian Geffon
2021-03-23 18:25 ` [PATCH v5 1/3] mm: Extend MREMAP_DONTUNMAP to non-anonymous mappings Brian Geffon
2021-03-23 18:25   ` [PATCH v5 2/3] Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio" Brian Geffon
2021-03-23 19:05     ` Dmitry Safonov
2021-03-23 18:25   ` [PATCH v5 3/3] selftests: Add a MREMAP_DONTUNMAP selftest for shmem Brian Geffon
2021-03-23 18:25   ` [PATCH] mremap.2: MREMAP_DONTUNMAP to reflect to supported mappings Brian Geffon
2021-03-25 21:34     ` Alejandro Colomar (man-pages)
2021-03-26 18:08       ` Brian Geffon
2022-05-10 20:50         ` Brian Geffon
2021-03-23 19:04   ` [PATCH v5 1/3] mm: Extend MREMAP_DONTUNMAP to non-anonymous mappings Dmitry Safonov

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