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 C96D71099B20 for ; Fri, 20 Mar 2026 17:03:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C83786B00E0; Fri, 20 Mar 2026 13:03:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C342E6B00E2; Fri, 20 Mar 2026 13:03:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B49D56B00E3; Fri, 20 Mar 2026 13:03:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id A2CE16B00E0 for ; Fri, 20 Mar 2026 13:03:23 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 5A873C16B5 for ; 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imf30.hostedemail.com; dkim=none; spf=pass (imf30.hostedemail.com: domain of youngjun.park@lge.com designates 156.147.51.103 as permitted sender) smtp.mailfrom=youngjun.park@lge.com; dmarc=pass (policy=none) header.from=lge.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774026201; a=rsa-sha256; cv=none; b=sR5YVOzM1ZuHWaIyLb1iGj3jAm/i7icKgQhFQ8vCu66mTo5lCzdqdzL/8MPl94NpER+9aW pgIft43kz+Bcal315yE5UcTKuDU0GqLKXWQXmdCWgHY+FENGs7rEXH1+q97p12HD11f/01 kJdtDu9X4g3hAvH9RfrnBPK11qMRxEk= Received: from unknown (HELO yjaykim-PowerEdge-T330.lge.net) (10.177.112.156) by 156.147.51.103 with ESMTP; 21 Mar 2026 02:03:14 +0900 X-Original-SENDERIP: 10.177.112.156 X-Original-MAILFROM: youngjun.park@lge.com From: Youngjun Park To: rafael@kernel.org, akpm@linux-foundation.org Cc: chrisl@kernel.org, kasong@tencent.com, pavel@kernel.org, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, baohua@kernel.org, youngjun.park@lge.com, usama.arif@linux.dev, linux-pm@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v6 0/3] mm/swap, PM: hibernate: fix swapoff race and optimize swap Date: Sat, 21 Mar 2026 02:03:10 +0900 Message-Id: <20260320170313.163386-1-youngjun.park@lge.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 725E880018 X-Rspamd-Server: rspam08 X-Stat-Signature: u71zi8pkf5dt5hwngo5a7bjiiraem7em X-HE-Tag: 1774026200-722527 X-HE-Meta: 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 kFd8fAWA e3yfKaPVrPIyNl1rnoydTENn4YfkcnfEnLZ1CqXqSQRRwm7EODdrNok0nk6+NTnJ+bov4GSqVCWvf2YeJq90NPqD/w42OgTKVOXafsNRCOLeGeBO5ZOpaS7CUgiUxx6Xv9jICfVH9sb4LGO+I49v9c+5P6zKAqwiyUAWC1hxItMJzsJqmFxHCk+SFAQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Currently, in the uswsusp path, only the swap type value is retrieved at lookup time without holding a reference. If swapoff races after the type is acquired, subsequent slot allocations operate on a stale swap device. Additionally, grabbing and releasing the swap device reference on every slot allocation is inefficient across the entire hibernation swap path. This patch series addresses these issues: - Patch 1: Fixes the swapoff race in uswsusp by pinning the swap device from the point it is looked up until the session completes. - Patch 2: Removes the overhead of per-slot reference counting in alloc/free paths and cleans up the redundant SWP_WRITEOK check. - Patch 3: Fixes a spurious WARNING in the uswsusp GFP mask restore path. (Found during uswsusp test) Links: RFC v1: https://lore.kernel.org/linux-mm/20260305202413.1888499-1-usama.arif@linux.dev/T/#m3693d45180f14f441b6951984f4b4bfd90ec0c9d RFC v2: https://lore.kernel.org/linux-mm/20260306024608.1720991-1-youngjun.park@lge.com/ RFC v3: https://lore.kernel.org/linux-mm/20260312112511.3596781-1-youngjun.park@lge.com/ v4: https://lore.kernel.org/linux-mm/abv+rjgyArqZ2uym@yjaykim-PowerEdge-T330/T/#m924fa3e58d0f0da488300653163ee8db7e870e4a v5: https://lore.kernel.org/linux-mm/ab0YEn+Fd41q6LM7@yjaykim-PowerEdge-T330/T/#m8409d470c68cb152b0849940759bff7d7806f397 Testing: - Hibernate/resume via sysfs (echo reboot > /sys/power/disk && echo disk > /sys/power/state) - Hibernate with suspend via sysfs (echo suspend > /sys/power/disk && echo disk > /sys/power/state) - Hibernate/resume via uswsusp (suspend-utils s2disk/resume on QEMU) - Verified swap I/O works correctly after resume. - Verified swapoff succeeds after snapshot resume completes. - Verified pm_restore_gfp_mask() WARNING no longer triggers (Patch 3). - Verified SNAPSHOT_FREEZE followed by snapshot_release() does not trigger pm_restore_gfp_mask() WARNING (Patch 3). - swapoff during active uswsusp session: - Verified swapoff returns -EBUSY while swap device is pinned (Patch 1). - Verified swapoff succeeds after uswsusp process terminates. Changelog: v5 -> v6: - Replaced get/put reference approach with SWP_HIBERNATION pinning to prevent swapoff, per Kairui's feedback. Renamed helpers from get/find/put_hibernation_swap_type() to pin/find/unpin_hibernation_swap_type(). - Removed swapoff waiting on hibernation reference. swapoff now returns -EBUSY immediately when the swap device is pinned. - Updated function comments per Kairui's review. - Updated commit message. - Fixed pm_restore_gfp_mask_safe() to use saved_gfp_count check instead of saved_gfp_mask, and hold system_transition_mutex for the check. Addressed AI review finding that SNAPSHOT_FREEZE followed by snapshot_release() could still trigger the WARNING. v4 -> v5: - Rebased onto v7.0-rc4 (Rafael J. Wysocki comment) - No functional changes. rebase conflict fix. rfc v3 -> v4: - Introduced get/find/put_hibernation_swap_type() helpers per Kairui's feedback. find_ for lookup-only, get/put for reference management. - Switched to swap_type_to_info() and added type < 0 check per Kairui's suggestion. - Fixed get_hibernation_swap_type() return when ref == false (Reviewed by Kairui) - Made swapoff wait interruptible to prevent hang when uswsusp holds a swap reference. - Fixed spurious WARN_ON in pm_restore_gfp_mask() by introducing pm_restore_gfp_mask_safe() (Patch 3). - Updated commit messages and added comments for clarity. - Rebased onto latest mm-new tree. rfc v2 -> rfc v3: - Split into 2 patches per Chris Li's feedback. - Simplified by not holding reference in normal hibernation path per Chris Li's suggestion. - Removed redundant SWP_WRITEOK check. - Rebased onto f543926f9d0c3f6dfb354adfe7fbaeedd1277c6b. rfc v1 -> rfc v2: - Squashed into single patch per Usama Arif's feedback. Youngjun Park (3): mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device mm/swap: remove redundant swap device reference in alloc/free PM: hibernate: fix spurious GFP mask WARNING in uswsusp path include/linux/suspend.h | 1 + include/linux/swap.h | 5 +- kernel/power/main.c | 18 ++++ kernel/power/swap.c | 2 +- kernel/power/user.c | 21 +++-- mm/swapfile.c | 178 +++++++++++++++++++++++++++++++--------- 6 files changed, 178 insertions(+), 47 deletions(-) base-commit: f338e77383789c0cae23ca3d48adcc5e9e137e3c -- 2.34.1