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Wed, 11 Nov 2020 03:37:24 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 0AB3Q9hA155728; Wed, 11 Nov 2020 03:37:23 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by userp3030.oracle.com with ESMTP id 34p5gxu4kh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 11 Nov 2020 03:37:23 +0000 Received: from abhmp0012.oracle.com (abhmp0012.oracle.com [141.146.116.18]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 0AB3bKdC023176; Wed, 11 Nov 2020 03:37:20 GMT Received: from [192.168.0.110] (/73.243.10.6) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 10 Nov 2020 19:37:20 -0800 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.20.0.2.21\)) Subject: Re: [PATCH] Assert that pages being written back are locked From: William Kucharski In-Reply-To: <20201027224645.GY20115@casper.infradead.org> Date: Tue, 10 Nov 2020 20:37:19 -0700 Cc: linux-mm@kvack.org Content-Transfer-Encoding: quoted-printable Message-Id: <590D2FE2-1BEF-497D-B572-80F26CDC9CDB@oracle.com> References: <20201027224645.GY20115@casper.infradead.org> To: Matthew Wilcox X-Mailer: Apple Mail (2.3654.20.0.2.21) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9801 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 mlxlogscore=999 mlxscore=0 spamscore=0 phishscore=0 adultscore=0 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011110015 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9801 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 lowpriorityscore=0 priorityscore=1501 clxscore=1015 malwarescore=0 mlxscore=0 spamscore=0 suspectscore=0 mlxlogscore=999 impostorscore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011110015 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Looks good. Reviewed-by: William Kucharski > On Oct 27, 2020, at 4:46 PM, Matthew Wilcox = wrote: >=20 > From: Matthew Wilcox (Oracle) >=20 > In write_cache_pages(), we rely on PageLock to prevent writeback from > starting on locked pages. I'm not sure if we document anywhere that = pages > that we're starting writes on must be locked, but having an assertion > will make it clear to users that this is required. >=20 > Signed-off-by: Matthew Wilcox (Oracle) >=20 > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index 3671568d433f..f83dd855594d 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -2774,6 +2774,8 @@ int __test_set_page_writeback(struct page *page, = bool keep_write) > struct address_space *mapping =3D page_mapping(page); > int ret, access_ret; >=20 > + VM_BUG_ON_PGFLAGS(!PageLocked(page), page); > + > lock_page_memcg(page); > if (mapping && mapping_use_writeback_tags(mapping)) { > XA_STATE(xas, &mapping->i_pages, page_index(page)); >=20