From patchwork Thu Jul 18 12:24:11 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 11048905 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id AA2D8746 for ; Thu, 18 Jul 2019 12:24:27 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 96C5A2873A for ; Thu, 18 Jul 2019 12:24:27 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8B05628710; Thu, 18 Jul 2019 12:24:27 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1597E286D5 for ; Thu, 18 Jul 2019 12:24:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 361AE6B0003; Thu, 18 Jul 2019 08:24:26 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 2EAFB8E0001; Thu, 18 Jul 2019 08:24:26 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1D8C56B0007; Thu, 18 Jul 2019 08:24:26 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from mail-qt1-f198.google.com (mail-qt1-f198.google.com [209.85.160.198]) by kanga.kvack.org (Postfix) with ESMTP id ED49F6B0003 for ; Thu, 18 Jul 2019 08:24:25 -0400 (EDT) Received: by mail-qt1-f198.google.com with SMTP id l9so24085196qtu.12 for ; Thu, 18 Jul 2019 05:24:25 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:date:from:to :cc:subject:message-id:mime-version:content-disposition; bh=H+TymQOnmdcKuZk9ttK0AqeJXUX/JIzSLYz7mBRh16k=; b=b91eUYrwJJeeGfpnI3fmyL01bhSvEkyZC24ZPJmcS44vNG5hNZjWWYRoV8ToHLEvT2 9Z/64029z82pOqQ7ZlOMwPrTSRvehF+79/LEeiGzSKT1V2Oz7Oumjf5jDOTl8d8/HI6+ 0z+h7+6osfZLnuApIEXqBi0KcgRUJ/zgEaKYG6YIiiagj2DsxumSOqVOSqM2Tfx1o01O HzBxrnAjV1K/TTZ3YxYXGc9r/iNChIJKyvEnGUeskar1xoBANoYYZNxM4ZKvUqqg2s9p pCo09mSL657K2xkA+H6H9MjdSkA+tcyajrc8mwvYQuR1eAfuGvMdpqax3eECjg6fjSDM dEAg== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of mst@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=mst@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com X-Gm-Message-State: APjAAAU0bCmMF+rsdhDqriFYA51R+nQAayG3N32BIcsjyTsGEBQ0u6I5 2e6H0e6oSmJOyS4aTfEQKqefS7SFREesfoMXlBUDvxaLelyOWTYqEzZ8huRxQJJ1dG8uAymvI/7 nrSPsNiGZPtrIwS87YR9n+261jRUDIB5E+ylsJ7wzRGk9SxIkzmMmCGhQjg0UUPlNug== X-Received: by 2002:ac8:7104:: with SMTP id z4mr31690705qto.52.1563452665692; Thu, 18 Jul 2019 05:24:25 -0700 (PDT) X-Google-Smtp-Source: APXvYqwy4GAC3zMfmPnbSjIaCjJ0jmLwcne9FBdInOgNHxT1PGWxW39D2vLIelt9Vixy9uU8Jj60 X-Received: by 2002:ac8:7104:: with SMTP id z4mr31690663qto.52.1563452665044; Thu, 18 Jul 2019 05:24:25 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1563452665; cv=none; d=google.com; s=arc-20160816; b=uIN8hPq6oZAH1qzqniJLAaBpepMrx4n310Zd4OjyKLsognqXS9WlhDqw3sNQcof0yL yrcYHydnOj6CecqGh7NwpqYESl1NVyRDEcHN+RNRBuYxQ/X0qTr9XqrYZIiLLJd/N98Z tWrovyYUyhjz9xpS8zMYA8v0NjnFAgiSHyeVPxku8fMGjydzDaU1T/5MYAM1FPsphBYC GZ1i07KdbZ4dh7r7nKqbGuAShGtuN4XQ2g6CYcq8qHgaJcKZUkZMCRw/8ohMISMLgyld W8pQPfvkyQTKJr86wKDD9tAFC0/3b/4DaifJ1ZD1Hxgxy7H/0X7Gh9htFtZMphSlCh0w baLg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-disposition:mime-version:message-id:subject:cc:to:from:date; bh=H+TymQOnmdcKuZk9ttK0AqeJXUX/JIzSLYz7mBRh16k=; b=Mbua720DFYOF0whidJ6iHOmm2bDgeQqSx6LhSmd7v2rxhQNjqpbW60tvbX5crXXnaO kJza6ccqhlA0KexQjM8wAR07Rv8mQysyVRHfXWX6mlGWpcYw2qz2U1YJre7Re1lJT74E 2MiqvUZHKNZNWzlg/wCHGV8DfzHMPHJI0BIa9bpfG0dsAH/1wfvKcxfq1gSgrcy+IY9F WRPIPdlbvyLI++qMYqJMgRegUAFcxq9yg71ITphNcT+rlVPs4wm7SLs8m8aO+RXr0HLl AtImjWBrWZvJP6uBYcFGVdQ5SZ7sgbpn8NUHBdKuwkoZyf5tW/KQbmJWezmBo9jKo7om HJvw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of mst@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=mst@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id q31si1919187qta.349.2019.07.18.05.24.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Jul 2019 05:24:25 -0700 (PDT) Received-SPF: pass (google.com: domain of mst@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of mst@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=mst@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3A909309264C; Thu, 18 Jul 2019 12:24:24 +0000 (UTC) Received: from redhat.com (ovpn-120-147.rdu2.redhat.com [10.10.120.147]) by smtp.corp.redhat.com (Postfix) with SMTP id 8FA4E60A35; Thu, 18 Jul 2019 12:24:19 +0000 (UTC) Date: Thu, 18 Jul 2019 08:24:11 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Wei Wang , Jason Wang , virtualization@lists.linux-foundation.org, linux-mm@kvack.org Subject: [PATCH v3 1/2] mm/balloon_compaction: avoid duplicate page removal Message-ID: <20190718122324.10552-1-mst@redhat.com> MIME-Version: 1.0 Content-Disposition: inline X-Mutt-Fcc: =sent X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Thu, 18 Jul 2019 12:24:24 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Wei Wang A #GP is reported in the guest when requesting balloon inflation via virtio-balloon. The reason is that the virtio-balloon driver has removed the page from its internal page list (via balloon_page_pop), but balloon_page_enqueue_one also calls "list_del" to do the removal. This is necessary when it's used from balloon_page_enqueue_list, but not from balloon_page_enqueue. Move list_del to balloon_page_enqueue, and update comments accordingly. Fixes: 418a3ab1e778 (mm/balloon_compaction: List interfaces) Signed-off-by: Wei Wang Signed-off-by: Michael S. Tsirkin --- mm/balloon_compaction.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c index 83a7b614061f..d25664e1857b 100644 --- a/mm/balloon_compaction.c +++ b/mm/balloon_compaction.c @@ -21,7 +21,6 @@ static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info, * memory corruption is possible and we should stop execution. */ BUG_ON(!trylock_page(page)); - list_del(&page->lru); balloon_page_insert(b_dev_info, page); unlock_page(page); __count_vm_event(BALLOON_INFLATE); @@ -47,6 +46,7 @@ size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, spin_lock_irqsave(&b_dev_info->pages_lock, flags); list_for_each_entry_safe(page, tmp, pages, lru) { + list_del(&page->lru); balloon_page_enqueue_one(b_dev_info, page); n_pages++; } @@ -128,13 +128,19 @@ struct page *balloon_page_alloc(void) EXPORT_SYMBOL_GPL(balloon_page_alloc); /* - * balloon_page_enqueue - allocates a new page and inserts it into the balloon - * page list. + * balloon_page_enqueue - inserts a new page into the balloon page list. + * * @b_dev_info: balloon device descriptor where we will insert a new page to * @page: new page to enqueue - allocated using balloon_page_alloc. * * Driver must call it to properly enqueue a new allocated balloon page * before definitively removing it from the guest system. + * + * Drivers must not call balloon_page_enqueue on pages that have been + * pushed to a list with balloon_page_push before removing them with + * balloon_page_pop. To all pages on a list, use balloon_page_list_enqueue + * instead. + * * This function returns the page address for the recently enqueued page or * NULL in the case we fail to allocate a new page this turn. */ From patchwork Thu Jul 18 12:24:24 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 11048907 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 768CC746 for ; Thu, 18 Jul 2019 12:24:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5F8D5286BE for ; Thu, 18 Jul 2019 12:24:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 53AE72882A; Thu, 18 Jul 2019 12:24:32 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8E179286BE for ; Thu, 18 Jul 2019 12:24:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 81BF86B0005; Thu, 18 Jul 2019 08:24:30 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 7CC0A6B0007; Thu, 18 Jul 2019 08:24:30 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 66D1C8E0001; Thu, 18 Jul 2019 08:24:30 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) by kanga.kvack.org (Postfix) with ESMTP id 438866B0005 for ; Thu, 18 Jul 2019 08:24:30 -0400 (EDT) Received: by mail-qk1-f199.google.com with SMTP id c79so23086157qkg.13 for ; Thu, 18 Jul 2019 05:24:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:date:from:to :cc:subject:message-id:references:mime-version:content-disposition :in-reply-to; bh=9e4f5Wm+7v+5gnl2N8Qt2KV0IZg5PpiXlQeQJbRykCw=; b=RSif91bisJ9N7i6JgMg8pzehdD6Ek3OcTXjrZJv9iBC4MXwNbFjZ2v4NgXDUoPBgBa aHg8ZSaE/7c0yplHerQcgyj4Yytf4OQxLE+Iw3M49jzv9ISCLrYxIezQHfdtLCJk7MMn O3DX/Ci9PrGAqs8+OHjM4O4oBd+ouoPgzNdkDyds/g2u7ihJMIg+gATZnMXGGnzWSdfc T8nFXlrBWfeUxIq9rnYfZnPeTwIComVVxdD8PkYv6lpbxE4n9VRwFaFC0A0MQSs0bWLa wpEWDClmsb5lgqgWIHkamaElpJ7KUL3pVXW1bsGG1us3kNa8vm1HdDlT1bJgGFt7ba0g /14w== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of mst@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=mst@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com X-Gm-Message-State: APjAAAXF9MBEuGq4WbtoH1zuJUajmcZoWTFQ5jTX+SgchKgobwj18b4D /cd7dTsaTvHmo5pbz0EYdx5MriaNcuYVn/3KA7Zn/yYN3xStC4eEOFo4ereYo/fPVzHEs1JuXmz nNQ9Wq1B0CO01UCKJ7YzLcDEYPtj2TiVyyOuYYPLn4m+mjdBbHCuj4CajHASEnQ6EHw== X-Received: by 2002:ae9:d606:: with SMTP id r6mr29882727qkk.364.1563452670024; Thu, 18 Jul 2019 05:24:30 -0700 (PDT) X-Google-Smtp-Source: APXvYqzqkH57gNDAASV9JwHI8GM3aDVT5dCSwKCjE7l/whGI+Fwnz8t6lJr+LdBFyoRHuW3hyGi0 X-Received: by 2002:ae9:d606:: with SMTP id r6mr29882652qkk.364.1563452668845; Thu, 18 Jul 2019 05:24:28 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1563452668; cv=none; d=google.com; s=arc-20160816; b=EUtkfrCe9xHV1HxzuBy9R0F0RW4BmCuDu9P33VrlaTbKr2SkimcF/LCQg1Xj7In7sX RK4O2FBter59LFPBpScP9EpfKNfL+P3pIKEm2ZEtH0IKxl6y5wesjkhq+scPetAjjg/I 9KnZ/6rFcVBnitkFsZP5Z++nJAJK3o3W2oeG+8nzb0QdPHXRQIWNN9XjLjJ+oh61YNXE X2whLNeD8pD1mEG8G3ALaxawYTHJDkACDbsV6JAaORfCujQ/fG/c89IOVdmiyTu0ZQ3A Ei/lZ8HBFlllb8R8c/SvS3SxlDgtJRUZCWn6zxB8wj7L4Kgi5pd+QucWrIzCnQ5r6apJ n3Sw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date; bh=9e4f5Wm+7v+5gnl2N8Qt2KV0IZg5PpiXlQeQJbRykCw=; b=YSUVFAIuGgell1Xj6S/BL9b1nzUsHEU6WfzKGP5bec/wNK2Tqxq8QvfKkUWYbs101D VnnAca954l34WHjuvoknw5uJhuJ/vgQ1NXIiwUHIAkiNaqrhWJ8nMas6SdQpXtp9PqyN lZBHDJlvhm1Quu7Nl8MfKINnXURKH6iFXl1RUPx5rRFZ+8xPbEau82CAolsfc8KZdLXV WPF7NP7hFVT/UToVq2fBIqnX0mQqsDTWo8UsMg9ZCQa4rrEj4IIcqxdMIRRfhAg8/Gnx vYTFCeP1Dd8mILD9Q45K6oRdakbsqJfEl1Ye9x+Q70U+u2/0pb8bD4VbonnP9ktq/T02 SCWg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of mst@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=mst@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id f44si18291754qtk.148.2019.07.18.05.24.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Jul 2019 05:24:28 -0700 (PDT) Received-SPF: pass (google.com: domain of mst@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of mst@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=mst@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1F9AC30C543E; Thu, 18 Jul 2019 12:24:28 +0000 (UTC) Received: from redhat.com (ovpn-120-147.rdu2.redhat.com [10.10.120.147]) by smtp.corp.redhat.com (Postfix) with SMTP id 2EE4F5C21A; Thu, 18 Jul 2019 12:24:25 +0000 (UTC) Date: Thu, 18 Jul 2019 08:24:24 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Wei Wang , Jason Wang , virtualization@lists.linux-foundation.org, linux-mm@kvack.org Subject: [PATCH v3 2/2] balloon: fix up comments Message-ID: <20190718122324.10552-2-mst@redhat.com> References: <20190718122324.10552-1-mst@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190718122324.10552-1-mst@redhat.com> X-Mutt-Fcc: =sent X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Thu, 18 Jul 2019 12:24:28 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Lots of comments bitrotted. Fix them up. Fixes: 418a3ab1e778 (mm/balloon_compaction: List interfaces) Signed-off-by: Michael S. Tsirkin Reviewed-by: Wei Wang --- mm/balloon_compaction.c | 73 +++++++++++++++++++++++------------------ 1 file changed, 41 insertions(+), 32 deletions(-) diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c index d25664e1857b..9cb03da5bcea 100644 --- a/mm/balloon_compaction.c +++ b/mm/balloon_compaction.c @@ -32,10 +32,10 @@ static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info, * @b_dev_info: balloon device descriptor where we will insert a new page to * @pages: pages to enqueue - allocated using balloon_page_alloc. * - * Driver must call it to properly enqueue a balloon pages before definitively - * removing it from the guest system. + * Driver must call this function to properly enqueue balloon pages before + * definitively removing them from the guest system. * - * Return: number of pages that were enqueued. + * Returns: number of pages that were enqueued. */ size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, struct list_head *pages) @@ -63,14 +63,15 @@ EXPORT_SYMBOL_GPL(balloon_page_list_enqueue); * @n_req_pages: number of requested pages. * * Driver must call this function to properly de-allocate a previous enlisted - * balloon pages before definetively releasing it back to the guest system. + * balloon pages before definitively releasing it back to the guest system. * This function tries to remove @n_req_pages from the ballooned pages and * return them to the caller in the @pages list. * - * Note that this function may fail to dequeue some pages temporarily empty due - * to compaction isolated pages. + * Note that this function may fail to dequeue some pages even if the balloon + * isn't empty - since the page list can be temporarily empty due to compaction + * of isolated pages. * - * Return: number of pages that were added to the @pages list. + * Returns: number of pages that were added to the @pages list. */ size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, struct list_head *pages, size_t n_req_pages) @@ -112,12 +113,14 @@ EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); /* * balloon_page_alloc - allocates a new page for insertion into the balloon - * page list. + * page list. * - * Driver must call it to properly allocate a new enlisted balloon page. - * Driver must call balloon_page_enqueue before definitively removing it from - * the guest system. This function returns the page address for the recently - * allocated page or NULL in the case we fail to allocate a new page this turn. + * Driver must call this function to properly allocate a new enlisted balloon page. + * Driver must call balloon_page_enqueue before definitively removing the page + * from the guest system. + * + * Returns: struct page address for the allocated page or NULL in case it fails + * to allocate a new page. */ struct page *balloon_page_alloc(void) { @@ -130,19 +133,15 @@ EXPORT_SYMBOL_GPL(balloon_page_alloc); /* * balloon_page_enqueue - inserts a new page into the balloon page list. * - * @b_dev_info: balloon device descriptor where we will insert a new page to + * @b_dev_info: balloon device descriptor where we will insert a new page * @page: new page to enqueue - allocated using balloon_page_alloc. * - * Driver must call it to properly enqueue a new allocated balloon page - * before definitively removing it from the guest system. + * Drivers must call this function to properly enqueue a new allocated balloon + * page before definitively removing the page from the guest system. * - * Drivers must not call balloon_page_enqueue on pages that have been - * pushed to a list with balloon_page_push before removing them with - * balloon_page_pop. To all pages on a list, use balloon_page_list_enqueue - * instead. - * - * This function returns the page address for the recently enqueued page or - * NULL in the case we fail to allocate a new page this turn. + * Drivers must not call balloon_page_enqueue on pages that have been pushed to + * a list with balloon_page_push before removing them with balloon_page_pop. To + * enqueue all pages on a list, use balloon_page_list_enqueue instead. */ void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, struct page *page) @@ -157,14 +156,24 @@ EXPORT_SYMBOL_GPL(balloon_page_enqueue); /* * balloon_page_dequeue - removes a page from balloon's page list and returns - * the its address to allow the driver release the page. + * its address to allow the driver to release the page. * @b_dev_info: balloon device decriptor where we will grab a page from. * - * Driver must call it to properly de-allocate a previous enlisted balloon page - * before definetively releasing it back to the guest system. - * This function returns the page address for the recently dequeued page or - * NULL in the case we find balloon's page list temporarily empty due to - * compaction isolated pages. + * Driver must call this to properly dequeue a previously enqueued page + * before definitively releasing it back to the guest system. + * + * Caller must perform its own accounting to ensure that this + * function is called only if some pages are actually enqueued. + * + * Note that this function may fail to dequeue some pages even if there are + * some enqueued pages - since the page list can be temporarily empty due to + * the compaction of isolated pages. + * + * TODO: remove the caller accounting requirements, and allow caller to wait + * until all pages can be dequeued. + * + * Returns: struct page address for the dequeued page, or NULL if it fails to + * dequeue any pages. */ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) { @@ -177,9 +186,9 @@ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) if (n_pages != 1) { /* * If we are unable to dequeue a balloon page because the page - * list is empty and there is no isolated pages, then something + * list is empty and there are no isolated pages, then something * went out of track and some balloon pages are lost. - * BUG() here, otherwise the balloon driver may get stuck into + * BUG() here, otherwise the balloon driver may get stuck in * an infinite loop while attempting to release all its pages. */ spin_lock_irqsave(&b_dev_info->pages_lock, flags); @@ -230,8 +239,8 @@ int balloon_page_migrate(struct address_space *mapping, /* * We can not easily support the no copy case here so ignore it as it - * is unlikely to be use with ballon pages. See include/linux/hmm.h for - * user of the MIGRATE_SYNC_NO_COPY mode. + * is unlikely to be used with ballon pages. See include/linux/hmm.h for + * a user of the MIGRATE_SYNC_NO_COPY mode. */ if (mode == MIGRATE_SYNC_NO_COPY) return -EINVAL;