From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 6230F1A6836; Sat, 18 Jul 2026 00:39:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784335144; cv=none; b=eq4sq9qaWvwyDGRAf+HO4Ho4IZ1ILXnDDZiYk5MNiiOhy9FQz6kMCBbPQXFeXtd/X9clh8QYYsnhf/UUAwR2y9tyiXiIo05qoyvNHrOZqW/mWLFsCepWaFWiaDI4HCaXjWDyMO3ExcS7U6FwwdTJdjsAA9hJqnftg+rrHvUBIxs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784335144; c=relaxed/simple; bh=Ryw7C8bV2E3jDC1FHuDIdbFaD960VXiPKTg9r91zi0w=; h=Date:To:From:Subject:Message-Id; b=a8gq8lwoLGb0/KDXBgG5jEoZtO4nx7dXhI2xL+BFTNCGsg4XfDp0zN2XtG1R9tzly0WbzHdm5VjmszKBHe2e3szeniux06hnmBWmSe+im5OyM8BqPLdeUVFShLmrACUIYNId0tgOmtbn4L+BJynLnPrkOETmCsCOytPRmoeRM2Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=T2dBZGt7; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="T2dBZGt7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6DD51F000E9; Sat, 18 Jul 2026 00:39:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1784335142; bh=HUrsN09Uz5fRzLg5+XmbScYtnZRRMu+zh/9mNVpZPP4=; h=Date:To:From:Subject; b=T2dBZGt7X/EQ+l5QvtUHBhyjnzt4S3/CopC3A0aQHQDmSyAfStYnV+SZjRX4/fOqP XRBbt7Md9vaQG6KHTegDq4TInXzpezS1PxyDA8sLD5BHzHWoyAWGqJX8dnyOgJch+I HtUQBycHG3WchxjIhH4+L8NKMRuaH01AD/WrU6rg= Date: Fri, 17 Jul 2026 17:39:02 -0700 To: mm-commits@vger.kernel.org,xuanzhuo@linux.alibaba.com,vbabka@kernel.org,stable@vger.kernel.org,rientjes@google.com,mst@redhat.com,jthoughton@google.com,jiaqiyan@google.com,jasowang@redhat.com,gthelen@google.com,david@redhat.com,david@kernel.org,alexander.duyck@gmail.com,linkl@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: + virtio_balloon-avoid-shrinker-execution-during-pm-suspend.patch added to mm-new branch Message-Id: <20260718003902.B6DD51F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: virtio_balloon: avoid shrinker execution during PM suspend has been added to the -mm mm-new branch. Its filename is virtio_balloon-avoid-shrinker-execution-during-pm-suspend.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/virtio_balloon-avoid-shrinker-execution-during-pm-suspend.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Link Lin Subject: virtio_balloon: avoid shrinker execution during PM suspend Date: Fri, 17 Jul 2026 00:22:21 +0000 During PM freeze (e.g. S4 hibernation), virtballoon_freeze() calls remove_common() which resets the virtio device and deletes all virtqueues. However, the balloon shrinker remains registered with core MM. If memory pressure occurs during S4 hibernation image creation/saving, MM invokes virtio_balloon_shrinker_scan(), which attempts to reclaim free pages. Although return_free_pages_to_mm() only frees pages back to MM, reclaiming free pages under memory pressure can trigger page reporting which might access the deleted reporting virtqueue if it is not yet frozen, or interact with other parts of the driver in a teardown state. Avoid this by adding a `suspended` flag to `struct virtio_balloon`. Set this flag to true in virtballoon_freeze() and false in virtballoon_restore(). Check this flag in both shrinker callbacks (scan and count) and return 0 if the device is suspended, preventing any shrinker execution while virtqueues are deleted. Wrap the lockless reads in READ_ONCE() and writes in WRITE_ONCE() to prevent compiler optimization issues and KCSAN data race warnings. Link: https://lore.kernel.org/20260717002311.681748-3-linkl@google.com Fixes: 71019de8219b ("virtio_balloon: Add free page hinting support") Signed-off-by: Link Lin Acked-by: David Rientjes Suggested-by: James Houghton Cc: Michael S. Tsirkin Cc: Alexander Duyck Cc: David Hildenbrand Cc: Greg Thelen Cc: Jason Wang Cc: Jiaqi Yan Cc: Vlastimil Babka Cc: Xuan Zhuo Cc: David Hildenbrand Cc: Signed-off-by: Andrew Morton --- drivers/virtio/virtio_balloon.c | 49 +++++++++++++++++++++++++----- 1 file changed, 41 insertions(+), 8 deletions(-) --- a/drivers/virtio/virtio_balloon.c~virtio_balloon-avoid-shrinker-execution-during-pm-suspend +++ a/drivers/virtio/virtio_balloon.c @@ -68,6 +68,8 @@ struct virtio_balloon { /* Prevent updating balloon when it is being canceled. */ spinlock_t stop_update_lock; bool stop_update; + /* Prevent shrinker from running while device is suspended. */ + bool suspended; /* Bitmap to indicate if reading the related config fields are needed */ unsigned long config_read_bitmap; @@ -471,9 +473,9 @@ static inline s64 towards_target(struct return target - vb->num_pages; } -/* Gives back @num_to_return blocks of free pages to mm. */ -static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb, - unsigned long num_to_return) +/* Helper: must be called with free_page_list_lock held */ +static unsigned long __return_free_pages_to_mm(struct virtio_balloon *vb, + unsigned long num_to_return) { unsigned long num_returned = 0; struct page *page, *next; @@ -481,8 +483,6 @@ static unsigned long return_free_pages_t if (unlikely(!num_to_return)) return 0; - spin_lock_irq(&vb->free_page_list_lock); - list_for_each_entry_safe(page, next, &vb->free_page_list, lru) { list_del(&page->lru); __free_pages(page, VIRTIO_BALLOON_HINT_BLOCK_ORDER); @@ -490,11 +490,27 @@ static unsigned long return_free_pages_t break; } vb->num_free_page_blocks -= num_returned; - spin_unlock_irq(&vb->free_page_list_lock); return num_returned; } +/* Gives back @num_to_return blocks of free pages to mm. */ +static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb, + unsigned long num_to_return) +{ + unsigned long ret; + + spin_lock_irq(&vb->free_page_list_lock); + if (vb->suspended) { + spin_unlock_irq(&vb->free_page_list_lock); + return 0; + } + ret = __return_free_pages_to_mm(vb, num_to_return); + spin_unlock_irq(&vb->free_page_list_lock); + + return ret; +} + static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb) { if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) @@ -871,6 +887,9 @@ static unsigned long virtio_balloon_shri { struct virtio_balloon *vb = shrinker->private_data; + if (READ_ONCE(vb->suspended)) + return 0; + return shrink_free_pages(vb, sc->nr_to_scan); } @@ -879,6 +898,9 @@ static unsigned long virtio_balloon_shri { struct virtio_balloon *vb = shrinker->private_data; + if (READ_ONCE(vb->suspended)) + return 0; + return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES; } @@ -1086,8 +1108,11 @@ static void remove_common(struct virtio_ update_balloon_size(vb); /* There might be free pages that are being reported: release them. */ - if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) - return_free_pages_to_mm(vb, ULONG_MAX); + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { + spin_lock_irq(&vb->free_page_list_lock); + __return_free_pages_to_mm(vb, ULONG_MAX); + spin_unlock_irq(&vb->free_page_list_lock); + } /* Now we reset the device so we can clean up the queues. */ virtio_reset_device(vb->vdev); @@ -1130,6 +1155,10 @@ static int virtballoon_freeze(struct vir * The workqueue is already frozen by the PM core before this * function is called. */ + spin_lock_irq(&vb->free_page_list_lock); + WRITE_ONCE(vb->suspended, true); + spin_unlock_irq(&vb->free_page_list_lock); + remove_common(vb); return 0; } @@ -1145,6 +1174,10 @@ static int virtballoon_restore(struct vi virtio_device_ready(vdev); + spin_lock_irq(&vb->free_page_list_lock); + WRITE_ONCE(vb->suspended, false); + spin_unlock_irq(&vb->free_page_list_lock); + if (towards_target(vb)) virtballoon_changed(vdev); update_balloon_size(vb); _ Patches currently in -mm which might be from linkl@google.com are mm-page_reporting-use-system_freezable_wq-to-fix-uaf-during-suspend.patch virtio_balloon-avoid-shrinker-execution-during-pm-suspend.patch