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Sat, 24 Jul 2021 14:57:39 -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 16OLuZvu175775 for ; Sat, 24 Jul 2021 21:57:38 GMT Received: from mx0b-00069f01.pphosted.com (mx0b-00069f01.pphosted.com [205.220.177.26]) by userp3020.oracle.com with ESMTP id 3a0a6mmyrn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Sat, 24 Jul 2021 21:57:38 +0000 Received: from pps.filterd (m0246580.ppops.net [127.0.0.1]) by mx0b-00069f01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 16OLrA8Q028873 for ; Sat, 24 Jul 2021 21:57:37 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 3a0850nxt9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Sat, 24 Jul 2021 21:57:37 +0000 Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1m7PeC-003gMt-NK; Sat, 24 Jul 2021 21:57:28 +0000 Date: Sat, 24 Jul 2021 21:57:28 +0000 From: Al Viro To: Andreas Gruenbacher 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 suspectscore=0 mlxscore=0 adultscore=0 lowpriorityscore=0 spamscore=0 bulkscore=0 phishscore=0 malwarescore=0 impostorscore=0 priorityscore=269 clxscore=269 mlxlogscore=732 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107240132 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=778 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-2107240133 Cc: cluster-devel , Jan Kara , Linux Kernel Mailing List , Christoph Hellwig , linux-fsdevel , Linus Torvalds , 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-2107240133 X-Proofpoint-GUID: MaF_QCkvY5pmnxdh1tEGjodJRUD0N9fz X-Proofpoint-ORIG-GUID: MaF_QCkvY5pmnxdh1tEGjodJRUD0N9fz On Sat, Jul 24, 2021 at 11:38:20PM +0200, Andreas Gruenbacher wrote: > Hmm, how could we have sub-page failure areas when this is about if > and how pages are mapped? If we return the number of bytes that are > accessible, then users will know if they got nothing, something, or > everything, and they can act accordingly. What I'm saying is that in situation when you have cacheline-sized poisoned areas, there's no way to get an accurate count of readable area other than try and copy it out. What's more, "something" is essentially useless information - the pages might get unmapped right as your function returns; the caller still needs to deal with partial copies. And that's a slow path by definition, so informing them of a partial fault-in is not going to be useful. As far as callers are concerned, it's "nothing suitable in the beginning of the area" vs. "something might be accessible". _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel