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 DA5F53B9D9F for ; Mon, 23 Mar 2026 16:08:26 +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=1774282112; cv=none; b=pNPaQFkdHeWEZIvv1txn5xaoEQclXzicV/E6VWMN1ew7Oa81SNtJypznyrGev+5IBjcEEw2HIOlc+sk+efSu4RszNcEpYRIcnLLjHOj9mE/DnxHCUgEbL38U86+zRxCT7V0BVcZzXi5p6Q6TMI+ddvfNcEZlrXlI+erQqbinsOM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774282112; c=relaxed/simple; bh=58UDlEsUqIyv5uMucWLbnEYkU0DG7+LHUZEfQ2e6YoE=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=jDjss6HLudWiE3r2HrCbbcFQz2OOht/ednW8sZuBeXaAUFPZO7EeoYJ5JQx8UvuEzopHwy2dkUOclUsrSj9dCT4/6wjRj2I+q2PrJqZlYxu6HQjHo8Y4FLhI/HiWuoNnarQvjbVqov4L3hgfo7vhaHYQgFgUNYVvGmSmsee6bf0= 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; 24 Mar 2026 01:08:24 +0900 X-Original-SENDERIP: 10.177.112.156 X-Original-MAILFROM: youngjun.park@lge.com From: Youngjun Park To: "Rafael J . Wysocki" , Andrew Morton Cc: Chris Li , Kairui Song , Pavel Machek , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Usama Arif , linux-pm@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v8 0/2] mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device Date: Tue, 24 Mar 2026 01:08:20 +0900 Message-Id: <20260323160822.1409904-1-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. Rebased onto mm-new per Andrew's suggestion [1]. The si->flags race flagged by AI review in v7 (between SWP_HIBERNATION and cont_lock in add_swap_count_continuation) and the proposed fixes discussed there (atomic ops for si->flags, or serializing with swap_lock) are all moot on mm-new since Kairui's series removed that code path entirely. kernel/power/ changes are small, so Andrew proposed carrying everything through mm-new. Rafael, could you ack the PM-side changes? Re-tested on mm-new (c51ea78c5466) with hibernate/resume cycles and uswsusp paths. Also ran an additional round of AI review against the rebased version, no new issues found. [1] https://lore.kernel.org/linux-mm/20260322093038.25a7fd51f5d564b85815db7a@linux-foundation.org/ 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 v6: https://lore.kernel.org/linux-mm/20260320182227.896f9ab62d62961b2caab5f7@linux-foundation.org/T/#m10ee3346cd8dcd052749105d9a8e2052dbf3bc80 v7: https://lore.kernel.org/linux-mm/ab/20260321103309.439265-1-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. - swapoff during active uswsusp session: - Verified swapoff returns -EBUSY while swap device is pinned (Patch 1). - Verified swapoff succeeds after uswsusp process terminates. Changelog: v7 -> v8: - Rebased onto mm-new per Andrew Morton's suggestion. - Clarified function comments (SWP_HIBERNATION pinning). - Re-tested and AI-reviewed on mm-new; no new issues found. v6 -> v7: - Dropped Patch 3 (pm_restore_gfp_mask fix) from series as it has no dependency on Patches 1-2. Will be sent separately. (Rafael J. Wysocki feedback) 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(). - Renamed swap_type_of() to __find_hibernation_swap_type() since it is now an internal helper with no external callers. - Removed swapoff waiting on hibernation reference. swapoff now returns -EBUSY immediately when the swap device is pinned. - Updated function comments per Kairui's review. v4 -> v5: - Rebased onto v7.0-rc4 (Rafael J. Wysocki comment) - No functional changes. rfc v3 -> v4: - Introduced get/find/put_hibernation_swap_type() helpers per Kairui's feedback. - Switched to swap_type_to_info() and added type < 0 check. - Fixed get_hibernation_swap_type() return when ref == false. - Made swapoff wait interruptible to prevent hang when uswsusp holds a swap reference. rfc v2 -> rfc v3: - Split into 2 patches per Chris Li's feedback. - Simplified by not holding reference in normal hibernation path. - Removed redundant SWP_WRITEOK check. rfc v1 -> rfc v2: - Squashed into single patch per Usama Arif's feedback. Youngjun Park (2): mm/swap, PM: hibernate: fix swapoff race in uswsusp by pinning swap device mm/swap: remove redundant swap device reference in alloc/free include/linux/swap.h | 5 +- kernel/power/swap.c | 2 +- kernel/power/user.c | 15 +++- mm/swapfile.c | 203 +++++++++++++++++++++++++++++++++---------- 4 files changed, 172 insertions(+), 53 deletions(-) base-commit: c51ea78c5466be89914cbfbe2618dea67026c2b1 -- 2.34.1