From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lgeamrelo03.lge.com (lgeamrelo03.lge.com [156.147.51.102]) (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 85F3A283C87 for ; Tue, 17 Mar 2026 18:13:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=156.147.51.102 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773771210; cv=none; b=AxIcXoIqV8b+5YcC2fVv8NYwqIDVTvTdgRXFCh2GMwARULmQrQ/18i7mwAo4NyXzy87UruMx7YAuMwfJy0JRTYPtpGYQdlIxUXAAF8jW8yEok1fpK2dJvaoNEP0fHQfxvJnMmxmGcs8JlXIITro86NKCkuP7K1LZ9TdhEchfDpY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773771210; c=relaxed/simple; bh=7HP/36qrEvHek3Xxi9f7GZXjZ5Nnh3eDd1xvUHzhiFE=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=qWuTnzXaluQAgQUqJDtBrwvMADSL/kHJK7JT1YCvhgjbkkK/9F7yhSHgcrh8Zo764w42MVQjFKscpGemgX2f7xs5OS5T/ZxWhmZMZ4ebtLMP7o9LowgFSlkH1cfXgXnxqUT1hluauQKnFWetkM3K2YZuxwHX7m0l1Qna5x2lWc0= 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=156.147.51.102 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 156.147.51.102 with ESMTP; 18 Mar 2026 03:13:19 +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 v4 0/3] mm/swap, PM: hibernate: fix swapoff race and optimize swap Date: Wed, 18 Mar 2026 03:13:15 +0900 Message-Id: <20260317181318.2517015-1-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 holding the swap device reference from the point the swap device is looked up. - 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. (Founded 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/ 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). - swapoff during active uswsusp session: - Verified swapoff blocks while uswsusp holds swap reference. - Verified swapoff can be cancelled by signal (e.g. Ctrl+C). - Verified swapoff succeeds after uswsusp process terminates. Changelog: 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 (Reviewd 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. Note: Kairui suggested adding WARN on NULL in put_hibernation_swap_type(), but kept silent return instead, as type can legitimately be -1 when snapshot_open() fails to find a matching swap device. swap_type_to_info() returns NULL for type < 0, so the cleanup path stays simple. 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 getting swap reference 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 | 4 +- kernel/power/main.c | 7 ++ kernel/power/swap.c | 2 +- kernel/power/user.c | 19 +++-- mm/swapfile.c | 154 +++++++++++++++++++++++++++------------- 6 files changed, 132 insertions(+), 55 deletions(-) -- base-commit: 7d47a508dfdc335c107fb00b4d9ef46488281a52 2.34.1