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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <3710261.1691764329@warthog.procyon.org.uk> <3888331.1691773627@warthog.procyon.org.uk> To: Linus Torvalds Cc: dhowells@redhat.com, Alexander Viro , Jens Axboe , Christoph Hellwig , Christian Brauner , Matthew Wilcox , jlayton@kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] iov_iter: Convert iterate*() to inline funcs MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <4032544.1692018789.1@warthog.procyon.org.uk> Date: Mon, 14 Aug 2023 14:13:09 +0100 Message-ID: <4032545.1692018789@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-Rspamd-Queue-Id: D7D29A0015 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: dfo4e5aju37dm8zi3x8etprdoxy71jii X-HE-Tag: 1692018797-365615 X-HE-Meta: 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 tD6pvFRj 3I2ZrWVTWhELUjmX8pkhXBqmQiIWHIejyKh6oBTZE20CjHV/N5iviMsVE7ku03ZiyUvmbA/3quQqz7TNsVgF56n061F9gFNSNC8Nc6eJ25G1TtnbuYexkiQRX3Ir2+RhW3v9rkv6HA3SeF4jhS1+KlqgWE/oV9X2byCoIiJc2LoUAO0fn8KzxbRbKiqk7z6+a0S3GI1sQbQxSA0ULshyalKnjD5/6dj6ePQsghJqA79MEzbM88X+Pi9dnS2xn+7wJbcu9OXf7boworsL2zrN9umtYMsJauBEVZhVr 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: Linus Torvalds wrote: > > So I think you need to remove the changes you did to > memcpy_from_iter(). The old code was an explicit conditional of direct > calls: > > if (iov_iter_is_copy_mc(i)) > return (void *)copy_mc_to_kernel(to, from, size); > return memcpy(to, from, size); > > and now you do that > > iov_iter_is_copy_mc(i) ? > memcpy_from_iter_mc : memcpy_from_iter); > > to pass in a function pointer. > > Not ok. Not ok at all. It may look clever, but function pointers are > bad. Avoid them like the plague. Yeah. I was hoping that the compiler would manage to inline that, but it just does an indirect call. I'm trying to avoid passing the iterator as that makes things bigger. I think I can probably share the extra argument used for passing checksums. David