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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20250812010237.B52F8C4CEED@smtp.kernel.org> References: <20250812010237.B52F8C4CEED@smtp.kernel.org> To: Andrew Morton , asmadeus@codewreck.org Cc: dhowells@redhat.com, mm-commits@vger.kernel.org, viro@zeniv.linux.org.uk, stable@vger.kernel.org, ryan@lahfa.xyz, maximilian@mbosch.me, ct@flyingcircus.io, brauner@kernel.org, arnout@bzzt.net Subject: Re: + iov_iter-iterate_folioq-fix-handling-of-offset-=-folio-size.patch added to mm-hotfixes-unstable branch Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <650363.1754991487.1@warthog.procyon.org.uk> Date: Tue, 12 Aug 2025 10:38:07 +0100 Message-ID: <650364.1754991487@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Thinking about it again, I think this: > @@ -168,6 +168,8 @@ size_t iterate_folioq(struct iov_iter *i > break; > > fsize = folioq_folio_size(folioq, slot); > + if (skip >= fsize) > + goto next; > base = kmap_local_folio(folio, skip); > part = umin(len, PAGE_SIZE - skip % PAGE_SIZE); > remain = step(base, progress, part, priv, priv2); > @@ -177,6 +179,7 @@ size_t iterate_folioq(struct iov_iter *i > progress += consumed; > skip += consumed; > if (skip >= fsize) { > +next: > skip = 0; > slot++; > if (slot == folioq_nr_slots(folioq) && folioq->next) { Would be much better done as: > @@ -168,6 +168,8 @@ size_t iterate_folioq(struct iov_iter *i > break; > > fsize = folioq_folio_size(folioq, slot); > + if (skip < fsize) { > base = kmap_local_folio(folio, skip); > part = umin(len, PAGE_SIZE - skip % PAGE_SIZE); > remain = step(base, progress, part, priv, priv2); > @@ -177,6 +179,7 @@ size_t iterate_folioq(struct iov_iter *i > progress += consumed; > skip += consumed; > + } > if (skip >= fsize) { > skip = 0; > slot++; > if (slot == folioq_nr_slots(folioq) && folioq->next) { With the stuff inside the braces suitably indented. The compiler should be able to optimise away the extra comparison. David