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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <4be974aa-2beb-9ae5-3f48-7dde6241b0c7@nvidia.com> References: <4be974aa-2beb-9ae5-3f48-7dde6241b0c7@nvidia.com> <20230124170108.1070389-1-dhowells@redhat.com> <20230124170108.1070389-3-dhowells@redhat.com> To: John Hubbard Cc: dhowells@redhat.com, Al Viro , Christoph Hellwig , Matthew Wilcox , Jens Axboe , "Jan Kara" , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, "Christoph Hellwig" , linux-mm@kvack.org Subject: Re: [PATCH v9 2/8] iov_iter: Add a function to extract a page list from an iterator MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <1353066.1674594631.1@warthog.procyon.org.uk> Date: Tue, 24 Jan 2023 21:10:31 +0000 Message-ID: <1353067.1674594631@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Rspamd-Queue-Id: 2055640023 X-Stat-Signature: cwhk3byfxygzkt1ezef79wawkx6zjbyc X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1674594636-685080 X-HE-Meta: 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 Ic8H8czl NUGO1z3tNY+9BQppcQPwC35FMQ0XFe6POAefK4jq+iS1hESDBr+LBQJATmZrYiavj7tNB2fAx0xhxYUbZNX1poeRiFnRB6ntjoH0pppWK3rMqXyWgNdcSHv69Y4v2Jx0L8MAXXqTqQaVR0/8JJoxDnIhDBk/yWS1Uqo60wPyZUZv0OADugkRXzAO8cp6xpnDeod1DZJsKkZI8TRAsPVoQIDDLDy7wOiqwnmCz2Fatt4IbXIBK/ana2HRKgZjHL6e5viqXlggWXPhc9OjrkLz8pll8Ca0mZ7uePjzoFVEtG5P8Ee8EvX3rjUg9PQ== 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: John Hubbard wrote: > > + for (;;) { > > + if (i->nr_segs == 0) > > + return 0; > > + maxsize = min(maxsize, i->bvec->bv_len - skip); > > + if (maxsize) > > + break; > > + i->iov_offset = 0; > > + i->nr_segs--; > > + i->kvec++; > > + skip = 0; > > + } > > + > > + skip += i->bvec->bv_offset; > > + page = i->bvec->bv_page + skip / PAGE_SIZE; > > + offset = skip % PAGE_SIZE; > > + *offset0 = offset; > > + > > + maxpages = want_pages_array(pages, maxsize, offset, maxpages); > > + if (!maxpages) > > + return -ENOMEM; > > Is it OK that the iov_iter position has been advanced, and left that way, > in the case of an early -ENOMEM return here? I think it should be okay. The for-loop at the top just skips over empty segments, so it doesn't really advance things. There is an error there, though: it should be i->bvec++, not i->kvec++ in the loop. David