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Wed, 10 Apr 2024 17:44:41 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 537ED2004B; Wed, 10 Apr 2024 17:44:39 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 265F920040; Wed, 10 Apr 2024 17:44:39 +0000 (GMT) Received: from p-imbrenda (unknown [9.152.224.66]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 10 Apr 2024 17:44:39 +0000 (GMT) Date: Wed, 10 Apr 2024 19:21:28 +0200 From: Claudio Imbrenda To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, Matthew Wilcox , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Janosch Frank , Gerald Schaefer , Thomas Huth Subject: Re: [PATCH v1 1/5] s390/uv: don't call wait_on_page_writeback() without a reference Message-ID: <20240410192128.2ad60f9b@p-imbrenda> In-Reply-To: <20240404163642.1125529-2-david@redhat.com> References: <20240404163642.1125529-1-david@redhat.com> <20240404163642.1125529-2-david@redhat.com> Organization: IBM X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: quQYV4TfkaiiQczU3ccpk_wYZvvsE-_7 X-Proofpoint-GUID: epvxi2EtwwiBH1sO2ThDb1y5i3tsUcrR X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-04-10_04,2024-04-09_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 mlxscore=0 adultscore=0 priorityscore=1501 bulkscore=0 malwarescore=0 spamscore=0 phishscore=0 suspectscore=0 mlxlogscore=999 lowpriorityscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2404010000 definitions=main-2404100130 On Thu, 4 Apr 2024 18:36:38 +0200 David Hildenbrand wrote: > wait_on_page_writeback() requires that no spinlocks are held and that > a page reference is held, as documented for folio_wait_writeback(). After oops > we dropped the PTL, the page could get freed concurrently. So grab a > temporary reference. > > Fixes: 214d9bbcd3a6 ("s390/mm: provide memory management functions for protected KVM guests") > Signed-off-by: David Hildenbrand Reviewed-by: Claudio Imbrenda > --- > arch/s390/kernel/uv.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c > index fc07bc39e698..7401838b960b 100644 > --- a/arch/s390/kernel/uv.c > +++ b/arch/s390/kernel/uv.c > @@ -314,6 +314,13 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb) > rc = make_page_secure(page, uvcb); > unlock_page(page); > } > + > + /* > + * Once we drop the PTL, the page may get unmapped and > + * freed immediately. We need a temporary reference. > + */ > + if (rc == -EAGAIN) > + get_page(page); > } > pte_unmap_unlock(ptep, ptelock); > out: > @@ -325,6 +332,7 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb) > * completion, this is just a useless check, but it is safe. > */ > wait_on_page_writeback(page); > + put_page(page); > } else if (rc == -EBUSY) { > /* > * If we have tried a local drain and the page refcount