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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <20230207171305.3716974-1-dhowells@redhat.com> <20230207171305.3716974-2-dhowells@redhat.com> <176199.1675872591@warthog.procyon.org.uk> To: Christoph Hellwig Cc: dhowells@redhat.com, Jens Axboe , Al Viro , Matthew Wilcox , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , Hillf Danton , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzbot+a440341a59e3b7142895@syzkaller.appspotmail.com, Christoph Hellwig , John Hubbard Subject: Re: [PATCH v12 01/10] vfs, iomap: Fix generic_file_splice_read() to avoid reversion of ITER_PIPE MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <531131.1675939830.1@warthog.procyon.org.uk> Date: Thu, 09 Feb 2023 10:50:30 +0000 Message-ID: <531132.1675939830@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 X-Stat-Signature: yn5bo8nyapt59bt9n79qtoyxxuyqzjbt X-Rspam-User: X-Rspamd-Queue-Id: 7022D1C0016 X-Rspamd-Server: rspam06 X-HE-Tag: 1675939838-509186 X-HE-Meta: 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 9wvNuhOY gb19lcpxkGJP95VA9Cs8wDcVtL2ZXRsMlERn+Bs+Srd9fzcnOK0QR7fTFq0Y6m/6u1XshnmLGDsRwpwF+7DHFpqoK+9HgaHvQLJLcdbJ51JQobfDp4bb2xSLSpWYXnfFJC+xVEj6vJjFzvx8hlEnyDBW3VKRaEm9AyFOT5+wd4uHLZgYyCXbgkEnZg1r9+lUL8gfy2RdNpQcECuq5eKivarZllLRBVt2kLC/O94oOfzZBBxh0RuSlq4SRTL22T4Ch6/et1yu9qgi0Goog4crBqnvqPQCpeIdCMz0+MuGcjnYSzx7RmeiAIrq7L5/gQ3vUVEZB/D98vcMmwgmIdj5pzS/NHYi95RZN4wn5dnLY33TMCBFErVcHi4S4EQ== 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: Christoph Hellwig wrote: > I defintively like the idea of killing ITER_PIPE. Isn't the 16 > folios in a folio tree often much less than what we could fit into > a single pipe buf? Unless you have a file system that can use > huge folios for buffered I/O and actually does this might significantly > limit performance. There's a loop there that repeats the filemap_get_pages() until either the pipe is full or we hit EOF, the same as in filemap_read() (upon which this is based). I want to use filemap_get_pages() if I can as that does all the readahead stuff. What might be nice, though, is if I could tell it to return rather than waiting for a folio to come uptodate if it has already returned a folio so that I can push the other side of the splice along whilst the read is in progress. David