From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 85ED7211A28 for ; Fri, 17 Jul 2026 00:24:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784247886; cv=none; b=AcylFhskQIJ+QjAlB4njB6U3NS/XWOikrbXnsEfd/mqHEnBNljoIop4gYd2CPGF1Ron1d+VKuMT9lkIiukjNZuaHDATRbter+iushtqaT36OvhHRv6pnf4x+8jqg1XVLomt1jNID2C+FmltmIwhldPvgW7pA1UWc7xucl910J5M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784247886; c=relaxed/simple; bh=JCyh+AtN6PAa02kmcYI4QuJSIXU7zu3BHW7iW+Zlpy0=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=pEC+GWgbE4QeIWtRu65K07r1tqzaPeJeEi0CBREXMoUbWNI2bf2Yr6eHtaEUlKbMR9pJBi6QjSVkal57otluxJL6K0SGcVx5ESz0qqfT2QOapFdvtoXX2ZSekzZ1JKMWy6ZrAZC3lfkTPCE3eqvnYLO51pBJ+RWKI/WP47Zc2+8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--linkl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=ZI4yXMxc; arc=none smtp.client-ip=209.85.216.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--linkl.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ZI4yXMxc" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-38dd87656d3so6167665a91.2 for ; Thu, 16 Jul 2026 17:24:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1784247884; x=1784852684; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=kvV/YUs48FxJuWf2yjxeyeKt50HRM0qCcCCbR1JgotU=; b=ZI4yXMxc8fFcATYQWBJmXgjV6gRM5jQ1EMNnri10Vxc2LAAaYNMP2/PgYx5QLOum94 Cxj5O1s8zrH1MTOcvujOcaElCGAAJSLG1Cj/B7hkFoNAHtNkCuA729tMK9cDd1hB9P9u polwWFeF5+F1bw1mIMCXjJJfLfWp+ujy0uqQ5Xi8F24FK/4tFDWNrSu1loUs+pmzo+qm uc18QTxPfARafGRh+NzarTy0JxZMPl7u4TCc8+EokUEJN7quEaf/VtAnwOxHBndFc0RD UtaA4AIyyBxf3B0PdL47QawgjnVuW8TYHrglyMMmTgerMPhpNmBu0nFXC/8j+x9u79V0 2JYw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784247884; x=1784852684; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=kvV/YUs48FxJuWf2yjxeyeKt50HRM0qCcCCbR1JgotU=; b=hbwO4DJJfmxh6EO7RXZw01RaE/7aPUGnl9ojRQBsuwFIjXJLGI+3LSh5AnaqnSepqS F0tF19BHDh0T9XbZTlckpvI7yYULykKtao7OZhDp7Qt2VJ9rAFXgib6BCmZFOVmlAFTJ oWjN4hOQ3tWcq/I5orA34YPFlRuDGJNk9R6rc1P0fIwdoHRWgY0Ebx3IA/SXNFT9vtX2 H80FWtpc644DV/sS0oGbkyvwWFR2V9cvthSCGEeCPQmmx0vXscFH8AO+6kTs/SmOJr/Y eiiMktiGDsAbHCNp1/YP9za48WjW9/FZDCv/pYkRdOLb0dyf41NlwWuTwXbz5tVz80ye pVWQ== X-Forwarded-Encrypted: i=1; AHgh+RqRr6neyR13V+lPTYry+XF28jEKcaXZtlU1sf9LzMA5wJUmbq0FSAPPibeMr8+wlzbJh0xdytE=@vger.kernel.org X-Gm-Message-State: AOJu0YxPhae8YEDkhNrX1PCtQ//dniecs+WPzEKKZzmU9Pxr8CWs1qZM UY0nmhTMzKiyQZCTS98ANvCeU0TjS2+khG8ZmeWhP2emTEWSD31Nh90U1kS6wvF0tKSbcsTgBa1 C0g== X-Received: from pjbds23.prod.google.com ([2002:a17:90b:8d7:b0:389:a1f7:c74d]) (user=linkl job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:1345:b0:37f:9ce1:cdb0 with SMTP id 98e67ed59e1d1-38e4b55aeccmr247935a91.30.1784247883538; Thu, 16 Jul 2026 17:24:43 -0700 (PDT) Date: Fri, 17 Jul 2026 00:22:21 +0000 In-Reply-To: <20260717002311.681748-1-linkl@google.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260717002311.681748-1-linkl@google.com> X-Mailer: git-send-email 2.55.0.229.g6434b31f56-goog Message-ID: <20260717002311.681748-3-linkl@google.com> Subject: [PATCH v2 2/2] virtio_balloon: avoid shrinker execution during PM suspend From: Link Lin To: Andrew Morton , Vlastimil Babka , "Michael S . Tsirkin" , David Hildenbrand Cc: virtualization@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, prasin@google.com, rientjes@google.com, duenwen@google.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, Ammar Faizi , jiaqiyan@google.com, ahwilkins@google.com, Greg Thelen , Alexander Duyck , jthoughton@google.com, stable@vger.kernel.org, Link Lin Content-Type: text/plain; charset="UTF-8" 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. Fixes: 71019de8219b ("virtio_balloon: Add free page hinting support") Cc: stable@vger.kernel.org Acked-by: David Rientjes Signed-off-by: Link Lin --- drivers/virtio/virtio_balloon.c | 49 +++++++++++++++++++++++++++------ 1 file changed, 41 insertions(+), 8 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 088b3a0e6c..38e1166a64 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/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 virtio_balloon *vb) 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_to_mm(struct virtio_balloon *vb, 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_to_mm(struct virtio_balloon *vb, 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_shrinker_scan(struct shrinker *shrinker, { 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_shrinker_count(struct shrinker *shrinker, { 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; } @@ -1089,8 +1111,11 @@ static void remove_common(struct virtio_balloon *vb) 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); @@ -1133,6 +1158,10 @@ static int virtballoon_freeze(struct virtio_device *vdev) * 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; } @@ -1148,6 +1177,10 @@ static int virtballoon_restore(struct virtio_device *vdev) 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); -- 2.55.0.229.g6434b31f56-goog