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Wed, 16 Aug 2023 15:19:02 +0100 From: David Laight To: 'David Howells' CC: Al Viro , Linus Torvalds , Jens Axboe , "Christoph Hellwig" , Christian Brauner , "Matthew Wilcox" , Jeff Layton , "linux-fsdevel@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH v3 2/2] iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc() Thread-Topic: [PATCH v3 2/2] iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc() Thread-Index: AQHZ0DpP/l59sWTPXU+UuQ9VGbJikq/s16Kg///6foCAACRpIA== Date: Wed, 16 Aug 2023 14:19:02 +0000 Message-ID: <3dabec5643b24534a1c1c51894798047@AcuMS.aculab.com> References: <03730b50cebb4a349ad8667373bb8127@AcuMS.aculab.com> <20230816120741.534415-1-dhowells@redhat.com> <20230816120741.534415-3-dhowells@redhat.com> <608853.1692190847@warthog.procyon.org.uk> In-Reply-To: <608853.1692190847@warthog.procyon.org.uk> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 58B661C0034 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: uzpqzo6oc87r98x7gn7umimxs5ixz9p5 X-HE-Tag: 1692195550-598978 X-HE-Meta: U2FsdGVkX1/ajDcVRJhHTNemwN1P9EJINnDOUcq8fPYOIszEoQkEPVf4gdnU9WP0MNJnSaGTLHu9Kn8CaaeRBmrLMaIYEn4A9y/dNAzDZOYwWngJqevFSP6KWVkOgt/L9yw2VqjV+efTRcT4OfNdDquss6S+BSutp0E/uhVCQbxO+VhDsvv4iB+rIZbLSt6JuinIeX/T8RZtmtUy5vZwUvPVXSJHz+Xq/NTHPcFq/B4CN9v+mYvYs+RmddBP7vPA2//6DuA6NPnoYBih5oCA2cSB5rGqYqBgRkIXcP+FRF3+AcPlnDFfSE2/f6wyuap0KlhOgDx28neTLbgkv5PSAC9KOUAlRC5kkKxb4Tl/UGUAN6FkaXidW7iS6HE7qWSyCMZv+8m98QyyRIjM8JaV5MTOT4YgkLt9QGysfOXdI04742hdVWYuK2nxHfAKDvEAb2R/FBm6/5YQFqOJGou51Ndi+3VvYelipizTxadLcSO6/UeiU1V+WpuSKxo28sYqZOSLGqz5Y15jaXvPfKJQsFcw5aXb/0iwdpissBIrnUZGEGxOI7gBI8PGNeBKEFmqkphAjyJ/Bex0OhNRSIiXOfyRpA9N+wKJtgWgEPXMW75qMDMgITxwSJYOX2o/b8uQ5cYoWzRMGSrp2mWKcc92VlfLWkLTe7ndqvogUZZlEla1RpJKNYgcSLmawhvcnTqIR/hx1+YhZsSqKkrhJ0nJ4AvFqa2ucQfcqC43olWljRBY3XRl6BfVdZNk2tXA3+blI0xKAsaB+XXY0M+P7YdKlNJX7vHY7lgqIAeYTODiGanZywzwWC+jbsW6NlTiUWRsEKHlUeAo9w3Szl9HH3sgpi0EiO2QNfT8JxGvaBUgYe5rfcU4kFphFEdLSlLHM/Tfg3+VwjPQfKNTUXOkgQCfZwAi13ukyxgkiYGxeF6BXb4QBmoWxzZBGFVF6kKvR+UOCyDXe9bp+DWwTX+icc0 2IJmPQCP zlHPI52FUniH3Fvyfgq0dFVsTu3PIn3EONDXgEv8+Sqgz3z39OORuwNWnJDcBQnvyaKenP44RlflWiVhgVTqpIX6f4XvYdFJ2Bznx7P6c4PWNfiIsE3vdQl1XJrya/yeG0eNvx1ERf8Iuv+TkZVNL9hnOpsZ1YXZWk7rvnIXmSusCt73Ce775kUpO32RioYxpDYlyk9BZypQ8vKbqW0swOm15hKOkj5MvhpgOqcg4Cdzi7Vu0f4HZPXHRFiLWmAQc73QW9zSSBoyAS9yJbljrzxpPJPXNSiv4nHlWfUs8/ocSz9qIaNVCocvAoT/rB0O8LmmVc7wrzVQpQz3DAAMzAfIkQw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.002431, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: David Howells > Sent: Wednesday, August 16, 2023 2:01 PM >=20 > David Laight wrote: >=20 > > > > Couldn't the relevant code directly call __copy_from_iter_mc() ? > > Or a version then checked iov_is_copy_mc() and then fell > > back to the standard function. >=20 > No, because the marked iterator is handed by the coredump code to > __kernel_write_iter() and thence on to who-knows-what driver - which will= call > copy_from_iter() or some such. $DRIVER shouldn't need to know about > ->copy_mc. What about ITER_BVEC_MC ?? =09David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1= PT, UK Registration No: 1397386 (Wales)