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Received: from viro by zeniv.linux.org.uk with local (Exim 4.96 #2 (Red Hat Linux)) id 1ppfJR-00B1x8-0S; Fri, 21 Apr 2023 01:11:45 +0000 Date: Fri, 21 Apr 2023 02:11:45 +0100 From: Al Viro To: David Howells Cc: Jens Axboe , Christoph Hellwig , Matthew Wilcox , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , Hillf Danton , Christian Brauner , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Christoph Hellwig , John Hubbard Subject: Re: [PATCH v18 09/15] iov_iter: Kill ITER_PIPE Message-ID: <20230421011145.GW3390869@ZenIV> References: <20230314220757.3827941-1-dhowells@redhat.com> <20230314220757.3827941-10-dhowells@redhat.com> <20230420222231.GT3390869@ZenIV> <20230420223657.GV3390869@ZenIV> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230420223657.GV3390869@ZenIV> X-Stat-Signature: 1u6qg46764hnfrpsb61daxm7byc5iud1 X-Rspam-User: X-Rspamd-Queue-Id: 1CE68C001A X-Rspamd-Server: rspam06 X-HE-Tag: 1682039528-597628 X-HE-Meta: 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 wpcegn7r 29JS+5/qsWQx6O+cZSBm1IMG76/UJybcsA9PWwr/dLF0X2TppxJHbjFASAUMEhE7balD4A6lMgOqDg6ZmanWVC7cd9KL5PJLmV0nVerwIXalInyNd2HO7sM2K5riIi+x0KF4UfY/U1h5G8mgGXE4q7hPWY92UvSAnvkbEFOtzCWA6RFx3/RDKl3k8+GM2k1W/OjzhQOwgdArsmEM64pGFPyeo5NrOnx/OF8VjDi/d7x5mD5ipNXxqxxmTCgylVKKNEvAqEfpamceOoeeLWbu6BMHVnFz1SFblglbO06VBcB3D3E7VxEKtf4pEW/6fd0sJ5PYw4YMi3cjbJvW774KnPDn53GjJTy0q7opW2a0YVElH0IErKuraxn1pesLWkeqliKtv/ANYC3zTR/E= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Apr 20, 2023 at 11:36:57PM +0100, Al Viro wrote: > Don't get me wrong - I'd love to kill ITER_PIPE off; it's just that tons > of ->splice_read() duplicating the corresponding ->read_iter() up to the > point where it would call generic_file_read_iter(), modulo ignoring > O_DIRECT case and then calling filemap_splice_read() instead... Painful > and asking for trouble down the road. FWIW, broken in this series: * a bunch of 9p variants (those could probably switch to direct) * afs * ceph (very likely) * ecryptfs (atime propagation) * dax on various filesystems (probably) * f2fs * gfs2 * nfs * ocfs2 * orangefs * xfs * zonefs (probably) * splice from UDP sockets, unless I'm misreading something. Your sock_splice_read() still falls back to generic_file_splice_read(), rather than to direct_splice_read() and sockets don't have O_DIRECT in flags. Neither do they have associated page cache ;-) Sure, we could provide a bunch of ->splice_read(), but then we'd have to make sure that all subsequent changes to matching ->read_iter() get duplicated - unless they are on O_DIRECT-only paths, that is...