From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0A2C7C43334 for ; Tue, 28 Jun 2022 11:49:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344843AbiF1Lt0 (ORCPT ); Tue, 28 Jun 2022 07:49:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344763AbiF1LtW (ORCPT ); Tue, 28 Jun 2022 07:49:22 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 40FED60D5 for ; Tue, 28 Jun 2022 04:49:20 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 950C160C17 for ; Tue, 28 Jun 2022 11:49:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 20E5BC3411D; Tue, 28 Jun 2022 11:49:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1656416959; bh=ewXraRXFyGceyyfsFsm4BPyvA5iL7r9gkdCOx5w1q7I=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=K5jMMp0Pkk8MewAyTL7qvqICQFQHDCTWvLKU9tu0rNhNaTUJugOT44a5gNNdO9kRn DCN9YNoxUBYOi6/xulexYHwV1jdIePEKafn/dSI24+RgMxMYHhnG1/yOn2NG9JB6hZ 2Yq5LJ8Ihy0VoGcMXSieS6+MP6LhKyvLDDBqhvSB329kWfuyNUYgWpe6td2ytOIg9i cnuzvUDxnUyhftpbJnx9Ktozkuw7vKmUWQx149FWXxHeh1r+D8Cu9kpL3eHUHM5MZN xU+EMReNj63o7SZy4ril9kgg4jLMFuOZdHfF3A3g4x+lVkebFFfZYJbk58uN9Qiq5X EBQVlXfuiX19Q== Message-ID: <3e0c848c0e80f6f1095a4432939869215e9a145b.camel@kernel.org> Subject: Re: [PATCH 26/44] unify pipe_get_pages() and pipe_get_pages_alloc() From: Jeff Layton To: Al Viro , linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , Jens Axboe , Christoph Hellwig , Matthew Wilcox , David Howells , Dominique Martinet , Christian Brauner Date: Tue, 28 Jun 2022 07:49:16 -0400 In-Reply-To: <20220622041552.737754-26-viro@zeniv.linux.org.uk> References: <20220622041552.737754-1-viro@zeniv.linux.org.uk> <20220622041552.737754-26-viro@zeniv.linux.org.uk> Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.44.2 (3.44.2-1.fc36) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, 2022-06-22 at 05:15 +0100, Al Viro wrote: > The differences between those two are > * pipe_get_pages() gets a non-NULL struct page ** value pointing to > preallocated array + array size. > * pipe_get_pages_alloc() gets an address of struct page ** variable that > contains NULL, allocates the array and (on success) stores its address in > that variable. >=20 > Not hard to combine - always pass struct page ***, have > the previous pipe_get_pages_alloc() caller pass ~0U as cap for > array size. >=20 > Signed-off-by: Al Viro > --- > lib/iov_iter.c | 49 +++++++++++++++++-------------------------------- > 1 file changed, 17 insertions(+), 32 deletions(-) >=20 > diff --git a/lib/iov_iter.c b/lib/iov_iter.c > index 5c985cf2858e..1c98f2f3a581 100644 > --- a/lib/iov_iter.c > +++ b/lib/iov_iter.c > @@ -1187,6 +1187,11 @@ unsigned long iov_iter_gap_alignment(const struct = iov_iter *i) > } > EXPORT_SYMBOL(iov_iter_gap_alignment); > =20 > +static struct page **get_pages_array(size_t n) > +{ > + return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL); > +} > + > static inline ssize_t __pipe_get_pages(struct iov_iter *i, > size_t maxsize, > struct page **pages, > @@ -1220,10 +1225,11 @@ static inline ssize_t __pipe_get_pages(struct iov= _iter *i, > } > =20 > static ssize_t pipe_get_pages(struct iov_iter *i, > - struct page **pages, size_t maxsize, unsigned maxpages, > + struct page ***pages, size_t maxsize, unsigned maxpages, > size_t *start) > { > unsigned int npages, off; > + struct page **p; > size_t capacity; > =20 > if (!sanity(i)) > @@ -1231,8 +1237,15 @@ static ssize_t pipe_get_pages(struct iov_iter *i, > =20 > *start =3D off =3D pipe_npages(i, &npages); > capacity =3D min(npages, maxpages) * PAGE_SIZE - off; > + maxsize =3D min(maxsize, capacity); > + p =3D *pages; > + if (!p) { > + *pages =3D p =3D get_pages_array(DIV_ROUND_UP(maxsize + off, PAGE_SIZE= )); > + if (!p) > + return -ENOMEM; > + } > =20 > - return __pipe_get_pages(i, min(maxsize, capacity), pages, off); > + return __pipe_get_pages(i, maxsize, p, off); > } > =20 > static ssize_t iter_xarray_populate_pages(struct page **pages, struct xa= rray *xa, > @@ -1394,41 +1407,13 @@ ssize_t iov_iter_get_pages(struct iov_iter *i, > return len - *start; > } > if (iov_iter_is_pipe(i)) > - return pipe_get_pages(i, pages, maxsize, maxpages, start); > + return pipe_get_pages(i, &pages, maxsize, maxpages, start); > if (iov_iter_is_xarray(i)) > return iter_xarray_get_pages(i, pages, maxsize, maxpages, start); > return -EFAULT; > } > EXPORT_SYMBOL(iov_iter_get_pages); > =20 > -static struct page **get_pages_array(size_t n) > -{ > - return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL); > -} > - > -static ssize_t pipe_get_pages_alloc(struct iov_iter *i, > - struct page ***pages, size_t maxsize, > - size_t *start) > -{ > - struct page **p; > - unsigned int npages, off; > - ssize_t n; > - > - if (!sanity(i)) > - return -EFAULT; > - > - *start =3D off =3D pipe_npages(i, &npages); > - n =3D npages * PAGE_SIZE - off; > - if (maxsize > n) > - maxsize =3D n; > - else > - npages =3D DIV_ROUND_UP(maxsize + off, PAGE_SIZE); > - *pages =3D p =3D get_pages_array(npages); > - if (!p) > - return -ENOMEM; > - return __pipe_get_pages(i, maxsize, p, off); > -} > - > static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i, > struct page ***pages, size_t maxsize, > size_t *_start_offset) > @@ -1511,7 +1496,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct io= v_iter *i, > return len - *start; > } > if (iov_iter_is_pipe(i)) > - return pipe_get_pages_alloc(i, pages, maxsize, start); > + return pipe_get_pages(i, pages, maxsize, ~0U, start); > if (iov_iter_is_xarray(i)) > return iter_xarray_get_pages_alloc(i, pages, maxsize, start); > return -EFAULT; Reviewed-by: Jeff Layton