From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 555A8CA5FC5 for ; Wed, 30 Sep 2026 23:17:48 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 005986B008C; Wed, 30 Sep 2026 19:17:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EF7A86B0092; Wed, 30 Sep 2026 19:17:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E0D526B0093; Wed, 30 Sep 2026 19:17:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id AD5296B008C for ; Wed, 30 Sep 2026 19:17:46 -0400 (EDT) Received: from smtpin04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 1BC19C0265 for ; Wed, 30 Sep 2026 23:17:46 +0000 (UTC) X-FDA: 85271992932.04.DB93CC3 Received: from mail-wr2-f12.google.com (mail-wr2-f12.google.com [74.125.225.76]) by imf23.hostedemail.com (Postfix) with ESMTP id 328F0140004 for ; Wed, 30 Sep 2026 23:17:44 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=chrisdown.name header.s=google header.b=Av9Dc2Cy; dmarc=pass (policy=quarantine) header.from=chrisdown.name; spf=pass (imf23.hostedemail.com: domain of chris@chrisdown.name designates 74.125.225.76 as permitted sender) smtp.mailfrom=chris@chrisdown.name ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790810264; b=GQd7sJ5qd+7grXqcycU65GK+iNksjH8t6JUY6zNQ03LeqJa//dyZAcU5SCUgSM43p/L53g O5VtblQ89mD1ruAjzWG260sXo9nx7rIgVeiMMyKK32WQVBafCtqbcViyoTsDxKUYsPmcNe WAFKNXs4bCbIfKhd53OLLGg9/QTghPQ= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=chrisdown.name header.s=google header.b=Av9Dc2Cy; dmarc=pass (policy=quarantine) header.from=chrisdown.name; spf=pass (imf23.hostedemail.com: domain of chris@chrisdown.name designates 74.125.225.76 as permitted sender) smtp.mailfrom=chris@chrisdown.name ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790810264; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding:in-reply-to: references:dkim-signature; bh=Qqmx+w7wWMgcq8gW6PkHYUS1zHw7Tje/ih/ffys9GY0=; b=3IPLsoW5iOApSQQRyyx50J1+GAUfYm9Mcl1rxdwNXLmq0+OAT1LvBRIshe4aa0G87/zYHT SwjuSxLFz6XPtDwFLHk2MX4WJ6kL6Ubo2xJHdOVXWJK17LNlkQ7yCGZJTrgaY1ZhSKNfEH Qu+HscB5yC9FNZ9SSaauNOS1rGlAhIQ= Received: by mail-wr2-f12.google.com with SMTP id ffacd0b85a97d-482f63546c3so4600364f8f.1 for ; Wed, 30 Sep 2026 16:17:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; t=1790810262; x=1791415062; darn=kvack.org; h=user-agent:content-disposition:content-type:mime-version:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=Qqmx+w7wWMgcq8gW6PkHYUS1zHw7Tje/ih/ffys9GY0=; b=Av9Dc2CyfaMhs6s8V+TAEiI14qdETaVMkap45Utw3swsEH5+3a2pE2bxo2JyBK8sKa El4hNURUo/mexCpkORYBt1Y/KOBtsaOiNkVmYfeOiUykrvWnEtNEcgRoACyniJSMtW48 jCNPRdukv2nN6K/zCrLplganT133wtv9buFfs= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790810262; x=1791415062; h=user-agent:content-disposition:content-type:mime-version:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to:content-type; bh=Qqmx+w7wWMgcq8gW6PkHYUS1zHw7Tje/ih/ffys9GY0=; b=cOFuK3CaHmkZ8TK0Au6z7PG7dQobge8znNAOQYcxzCRW8uegC1D7f9NwM7lvQS59pq XN4SUzIImWzLdPL73z5itcfBS05zB5VLmUi+3GTkyPp7+I7F0m+yUW5m8LtGI9hqIlPd E/MNHicDn4HtpDbbxTP5cFpt7+DZ00vQqD2LvOACbho/GQ6UxILViLaF45pLo5ljZuJ7 iepL9yzQa6s6QJrbqQB3lQt98TcTfHNNt+Zn1DCggmvXrlH4kA8dYJE8sfQZktCBulkO uWAdYTgcw57FxO7/Z74m+aOPiQoKQIOQeXWh2xc7/VYsVgJOhGds9EmLPp+99JtmscuC VXuA== X-Forwarded-Encrypted: i=1; AKwUvBySo8rVdvZflDr/8dmisdxsaIkRSbhJhv3H9P/+rXfCRfX6fzbNFHESE8I7b9tVmHKCsPgATyHwdQ==@kvack.org X-Gm-Message-State: AFq9FYJcbljyZWlQNXLufKjepvgmcjNkR/Gzzc108I/36mEwU9JaiaIM 01jlJD8zL02MQnMlx0EJspQCSZP8WL3SVZZ5KBpuwD2cgeek4gs8pJu9tG2dvwIfm8E= X-Gm-Gg: AYBFou17q6ogDcc7qol3XulSYIAxW6RjNNU8Ss31+FMjrxgf02NIQDp/mNfpZ9nHlTp 5DKXStPSVe0CYQW4ZWwCAX0hyWMjhmeONetSAbDJGscB46IopGoL0XiEk8vo5/3rNwjC3OAAWvs PGemrrl88GdfuIzgpf3W5aFsES9nnz4nIG2LTrBOCauaoncmrD5Gdl8L+ee0yJ2O7THV8g6IOHT SwRk7rdjQB5nMTjv0gIsIsERBSGnGq1Qv5t+ytkUw67GDTUsQKnUbw6jLV6/U+E9tkRRCgH9E5l Enxdvz8xK0KO+M2GpqoaC/5XmXHex/r8ilqvNQBnigLKVNr//Dp2Ba7QGsjL7YfIPNwa4u1i+XT lPqPzekQJGwGAHNWsh1jkEbIECKQa8IGqEEznUbwH3vRlz4PxET5f3iIlHPwCmo7LuUyEr/jNIN g44PUJpUupzCXSGA5gFMP6P2o7rWqVaO1p8s/IH9cee2kpZQ4mrcrlFPP2JIQGlcCj12DrDjZi0 x+YLVmN+i7P6MxsEiSUIb5sq60= X-Received: by 2002:a05:6000:4811:b0:488:8546:d0b2 with SMTP id ffacd0b85a97d-48b0253956cmr6174897f8f.51.1790810262482; Wed, 30 Sep 2026 16:17:42 -0700 (PDT) Received: from localhost ([213.61.32.212]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48b0690e060sm2332276f8f.19.2026.09.30.16.17.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Sep 2026 16:17:41 -0700 (PDT) Date: Thu, 1 Oct 2026 01:17:40 +0200 From: Chris Down To: Andrew Morton Cc: Hugh Dickins , Baolin Wang , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Ying Huang , Kelley Nielsen , Vineeth Pillai , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: [PATCH] mm: Make swapoff interruptible when unusing mms/shmem Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/2.3.3 (9073d26d) (2026-06-12) X-Rspamd-Server: rspam06 X-Stat-Signature: rc9shs9utoxrnisubidt94zaa3e7ayrk X-Rspam-User: X-Rspamd-Queue-Id: 328F0140004 X-HE-Tag: 1790810264-669632 X-HE-Meta: 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 W/x9UvnM 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: try_to_unuse() only checks for a pending signal between mms, and shmem_unuse() doesn't check at all. That means that once swapoff gets to a process or a shmem file with a lot swapped out, nothing can interrupt it until every last page of it has been read back in. Just as one example of where this can concretely show up, freezing tasks for suspend or hibernation has to wait for swapoff to notice the freezer's fake signal, and gives up after freeze_timeout_msecs (20 seconds by default). Here's a facetious example where one swaps out 2GiB of one process to a swap file on ext4, starts swapoff, and half a second later tries to freeze with pm_test=freezer. Writing to /sys/power/state then fails with EBUSY and this in dmesg: Freezing user space processes failed after 20.003 seconds (1 tasks refusing to freeze, wq_busy=0): task:swapoff state:D stack:0 pid:3175 tgid:3175 ppid:2955 task_flags:0x400100 flags:0x00000419 Call trace: [...] io_schedule+0x44/0x70 folio_wait_bit_common+0x1ec/0x3d0 __folio_lock+0x24/0x40 unuse_pte_range+0x2d0/0x348 unuse_vma+0x158/0x248 unuse_mm+0xfc/0x150 try_to_unuse+0x104/0x3f8 __do_sys_swapoff+0x220/0x5d8 [...] The same goes for anything else that wants swapoff to stop, like an admin hitting ^C in a panic, of course. Prior to commit b56a2d8af914 ("mm: rid swapoff of quadratic complexity") try_to_unuse() was driven by find_next_to_unuse() which checks for a signal before every entry, so let's restore that behaviour. Just as an example of the improvements, here's how long freezing takes in the same test while swapoff is happening on my computer: before after 400MiB anon 8.925s 0.028s 400MiB shmem 1.639s 0.003s 2GiB anon failed after 20.003s 0.011s Fixes: b56a2d8af914 ("mm: rid swapoff of quadratic complexity") Signed-off-by: Chris Down --- mm/shmem.c | 4 ++++ mm/swapfile.c | 2 ++ 2 files changed, 6 insertions(+) diff --git a/mm/shmem.c b/mm/shmem.c index ae08cff4500c..72c8a61db76f 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1742,6 +1742,10 @@ static int shmem_unuse_inode(struct inode *inode, unsigned int type) if (ret < 0) break; + if (signal_pending(current)) { + ret = -EINTR; + break; + } start = indices[folio_batch_count(&fbatch) - 1]; } while (true); diff --git a/mm/swapfile.c b/mm/swapfile.c index 254ce86fa923..c3288910b3e3 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2689,6 +2689,8 @@ static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, pmd = pmd_offset(pud, addr); do { cond_resched(); + if (signal_pending(current)) + return -EINTR; next = pmd_addr_end(addr, end); ret = unuse_pte_range(vma, pmd, addr, next, type); if (ret) base-commit: 2ddb90ee544ae97215afc4698dc223293997cc43 -- 2.50.1