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Sat, 24 Jul 2021 13:26:39 -0700 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 16OKQZqv027617 for ; Sat, 24 Jul 2021 20:26:38 GMT Received: from mx0b-00069f01.pphosted.com (mx0b-00069f01.pphosted.com [205.220.177.26]) by userp3020.oracle.com with ESMTP id 3a0a6mjay8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Sat, 24 Jul 2021 20:26:37 +0000 Received: from pps.filterd (m0246577.ppops.net [127.0.0.1]) by mx0b-00069f01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 16OKEBQD031322 for ; Sat, 24 Jul 2021 20:26:36 GMT Received: from zeniv-ca.linux.org.uk (zeniv-ca.linux.org.uk [142.44.231.140]) by mx0b-00069f01.pphosted.com with ESMTP id 3a0c4ecab9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Sat, 24 Jul 2021 20:26:35 +0000 Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1m7OC1-003eaC-FU; Sat, 24 Jul 2021 20:24:17 +0000 Date: Sat, 24 Jul 2021 20:24:17 +0000 From: Al Viro To: Linus Torvalds Message-ID: References: <20210724193449.361667-1-agruenba@redhat.com> <20210724193449.361667-2-agruenba@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Source-IP: 142.44.231.140 X-ServerName: zeniv-ca.linux.org.uk X-Proofpoint-SPF-Result: None X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10055 signatures=668682 X-Proofpoint-Spam-Details: rule=tap_notspam policy=tap score=0 malwarescore=0 bulkscore=0 phishscore=0 mlxscore=0 adultscore=0 lowpriorityscore=0 suspectscore=0 impostorscore=0 priorityscore=78 mlxlogscore=788 spamscore=0 clxscore=249 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107240122 domainage_hfrom=9123 X-Spam: Clean X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10055 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxlogscore=842 phishscore=0 suspectscore=0 adultscore=0 mlxscore=0 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107240123 Cc: cluster-devel , Jan Kara , Andreas Gruenbacher , Linux Kernel Mailing List , Christoph Hellwig , linux-fsdevel , ocfs2-devel@oss.oracle.com Subject: Re: [Ocfs2-devel] [PATCH v4 1/8] iov_iter: Introduce iov_iter_fault_in_writeable helper X-BeenThere: ocfs2-devel@oss.oracle.com X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: ocfs2-devel-bounces@oss.oracle.com Errors-To: ocfs2-devel-bounces@oss.oracle.com X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10055 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 bulkscore=0 phishscore=0 malwarescore=0 spamscore=0 mlxlogscore=999 mlxscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107240123 X-Proofpoint-ORIG-GUID: w5ub7siehEfS5WewrcbwC1IpAvo9ntlF X-Proofpoint-GUID: w5ub7siehEfS5WewrcbwC1IpAvo9ntlF On Sat, Jul 24, 2021 at 12:52:34PM -0700, Linus Torvalds wrote: > ... > > + if (fault_in_user_pages(start, len, true) != len) > > + return -EFAULT; > > Looking at this once more, I think this is likely wrong. > > Why? > > Because any user can/should only care about at least *part* of the > area being writable. > > Imagine that you're doing a large read. If the *first* page is > writable, you should still return the partial read, not -EFAULT. Agreed. > So I think the code needs to return 0 if _any_ fault was successful. s/any/the first/... The same goes for fault-in for read, of course; I've a half-baked conversion to such semantics (-EFAULT vs. 0; precise length is unreliable anyway, especially if you have sub-page failure areas), need to finish and post it... _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel