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Wed, 10 Apr 2024 17:44:42 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C543320043; Wed, 10 Apr 2024 17:44:40 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 982C120040; Wed, 10 Apr 2024 17:44:40 +0000 (GMT) Received: from p-imbrenda (unknown [9.152.224.66]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 10 Apr 2024 17:44:40 +0000 (GMT) Date: Wed, 10 Apr 2024 19:32:10 +0200 From: Claudio Imbrenda To: David Hildenbrand Cc: Matthew Wilcox , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Janosch Frank , Gerald Schaefer , Thomas Huth Subject: Re: [PATCH v1 2/5] s390/uv: convert gmap_make_secure() to work on folios Message-ID: <20240410193210.61f3e069@p-imbrenda> In-Reply-To: <67557c5b-afd8-4578-a00d-6750accc1026@redhat.com> References: <20240404163642.1125529-1-david@redhat.com> <20240404163642.1125529-3-david@redhat.com> <67557c5b-afd8-4578-a00d-6750accc1026@redhat.com> Organization: IBM X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: Cunzjy_HxNYjM4_b2ia_0WbkCwexYEl6 X-Proofpoint-GUID: df6pIICEe-2EkmOQDiuilxJEEgdxbzxm 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 suspectscore=0 malwarescore=0 mlxlogscore=909 bulkscore=0 adultscore=0 phishscore=0 priorityscore=1501 mlxscore=0 spamscore=0 lowpriorityscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2404010000 definitions=main-2404100130 X-Rspamd-Queue-Id: C7D73140023 X-Rspam-User: X-Stat-Signature: rocpyqm7m3gt68r35an7x9pd5nt7ykmh X-Rspamd-Server: rspam01 X-HE-Tag: 1712771096-180776 X-HE-Meta: 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 OTrr1uL4 FtLZ3mwtb0fWhHLoMzS0iWOjylFBxJbmFMxV5e6uDFjXmFQfPvDbCvjqJy+pemYlJkBJWAHE6sl69aMg+4K510vwoO5u89KNxn7K81EbngOcRg5++ioXQtZtt/6oneRjWRDuA4vNfTBFIh4sTPq9OSV16ahNMR0XdBibM6I57/f007IUXWJSCS/LkL1tABf/qKBauw4WqC7f5Avl1qAyGxoC4aLB+20zC984LmzxfP+hJJoQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.002297, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 5 Apr 2024 09:09:30 +0200 David Hildenbrand wrote: > On 05.04.24 05:29, Matthew Wilcox wrote: > > On Thu, Apr 04, 2024 at 06:36:39PM +0200, David Hildenbrand wrote: > >> + /* We might get PTE-mapped large folios; split them first. */ > >> + if (folio_test_large(folio)) { > >> + rc = -E2BIG; > > > > We agree to this point. I just turned this into -EINVAL. > > > >> > >> + if (rc == -E2BIG) { > >> + /* > >> + * Splitting might fail with -EBUSY due to unexpected folio > >> + * references, just like make_folio_secure(). So handle it > >> + * ahead of time without the PTL being held. > >> + */ > >> + folio_lock(folio); > >> + rc = split_folio(folio); > >> + folio_unlock(folio); > >> + folio_put(folio); > >> + } > > > > Ummm ... if split_folio() succeeds, aren't we going to return 0 from > > this function, which will be interpreted as make_folio_secure() having > > succeeded? > > I assume the code would have to handle that, because it must deal with > possible races that would try to convert the folio page. > > But the right thing to do is > > if (!rc) > goto again; > > after the put. yes please