From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lgeamrelo07.lge.com (lgeamrelo07.lge.com [156.147.51.103]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CC1483D0914 for ; Fri, 20 Mar 2026 17:03:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=156.147.51.103 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774026206; cv=none; b=a/nipiTmcfXrpTU5amAwKeoJrBf2oGwYGFFq/hfaMJVpmgYZOsbIgIcF5G6vTrYfSUmfZMTpMOUd6jJsHYnqSA2jJpoTj0C3Zg5SdCVeiShG6kyVjJSFMH5Sr8bHhe22xDiE8hzwBq7LVPuoIB4iUfGO5Y2mA3s3qAIewW/yvyk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774026206; c=relaxed/simple; bh=tOsfc8vGXSTckwD4O/zUMHNKk1lqXzlTXuZPqMotYA0=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=EvU+DBWDuJFnjI+IFzBBKU5+NQxuWu2biPNOUAiZJ9f+/1jaXW53M5YuFOs0+aHGvhABrhXF0sWeUmxJF8LMm0dtbY+VBgPz88vwTq7HpdRXUl5JfR/6UX6bGIx9z0XBtI1NYWj8nsUUUqWgJPFhrws5XtopDoAYfIA00ndlTkU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lge.com; spf=pass smtp.mailfrom=lge.com; arc=none smtp.client-ip=156.147.51.103 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lge.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lge.com 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 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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