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Date: Thu, 13 Feb 2020 15:08:13 +0300 From: "Kirill A. Shutemov" <kirill@...temov.name> To: Brian Geffon <bgeffon@...gle.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, "Michael S . Tsirkin" <mst@...hat.com>, Arnd Bergmann <arnd@...db.de>, LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>, linux-api@...r.kernel.org, Andy Lutomirski <luto@...capital.net>, Will Deacon <will@...nel.org>, Andrea Arcangeli <aarcange@...hat.com>, Sonny Rao <sonnyrao@...gle.com>, Minchan Kim <minchan@...nel.org>, Joel Fernandes <joel@...lfernandes.org>, Yu Zhao <yuzhao@...gle.com>, Jesse Barnes <jsbarnes@...gle.com>, Nathan Chancellor <natechancellor@...il.com>, Florian Weimer <fweimer@...hat.com> Subject: Re: [PATCH v4] mm: Add MREMAP_DONTUNMAP to mremap(). On Mon, Feb 10, 2020 at 06:12:39AM -0800, Brian Geffon wrote: > Hi Kirill, > If the old_len == new_len then there is no change in the number of > locked pages they just moved, if the new_len < old_len then the > process of unmapping (new_len - old_len) bytes from the old mapping > will handle the locked page accounting. So in this special case where > we're growing the VMA, vma_to_resize() will enforce that growing the > vma doesn't exceed RLIMIT_MEMLOCK, but vma_to_resize() doesn't handle > incrementing mm->locked_bytes which is why we have that special case > incrementing it here. But if you do the operation for the VM_LOCKED vma, you'll have two locked VMA's now, right? Where do you account the old locked vma you left behind? -- Kirill A. Shutemov
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