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bh=nySyZPhsagsFnW6WdYB1/upY4dQT7wVe+Rq+dBuKfd8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=am5y7Vfn+XFGLbNK2LQDtZGjAbzxlEYncEa5SPc3AVzkP3qr/DFV69QXaqExXxDmD d+yo2YHUfwOt7ez9bbqNtPZsA54M5ueKdVOBwHktWDlP52M4CwkN7yhjNicwJiMnZ8 KXkwhz5+vje7ldNNaYRaB4uAsUuxFOjjVw5IGuV4= Date: Thu, 22 Dec 2022 16:56:52 -0800 From: Andrew Morton To: "Zach O'Keefe" Cc: linux-mm@kvack.org, Hugh Dickins , Yang Shi Subject: Re: [PATCH] mm/MADV_COLLAPSE: don't expand collapse when vm_end is past requested end Message-Id: <20221222165652.3775ff5343580e02ffabfa23@linux-foundation.org> In-Reply-To: <20221223003953.2795313-1-zokeefe@google.com> References: <20221223003953.2795313-1-zokeefe@google.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 16147100005 X-Stat-Signature: gumfpnxk3xgkncwjome4pwzuujyz115w X-HE-Tag: 1671757016-743822 X-HE-Meta: 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 jWenKDQX 9TY1TYq3AUvlhOMM1Vtl10/ATqCxEF75jILdhsa4mdW2S+OudnbIR9xzEohbbhYs7peUTNUfffXpRDlVeFbWsFYUzZDO+n7YGGI8YwPkSO2fgDNhov9dxSmmDhQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 22 Dec 2022 16:39:53 -0800 "Zach O'Keefe" wrote: > MADV_COLLAPSE acts on one hugepage-aligned/sized region at a time, until > it has collapsed all eligible memory contained within the bounds > supplied by the user. > > At the top of each hugepage iteration we (re)lock mmap_lock and > (re)validate the VMA for eligibility and update variables that might > have changed while mmap_lock was dropped. One thing that might occur, > is that the VMA could be resized, and as such, we refetch vma->vm_end > to make sure we don't collapse past the end of the VMA. > > However, it's possible that during this refetch that we expand the > region acted on by MADV_COLLAPSE if vma->vm_end is greater than the end > of the user-supplied range. > > Don't expand the acted-on region when refetching vma->vm_end. What are the user-visible effects of this? > Fixes: 4d24de9425f7 ("mm: MADV_COLLAPSE: refetch vm_end after reacquiring mmap_lock") Should we backport "mm/shmem: restore SHMEM_HUGE_DENY precedence over MADV_COLLAPSE" and/or this patch into 6.1.x?