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 E8A58C433EF for ; Sat, 18 Jun 2022 11:15:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232966AbiFRLPZ (ORCPT ); Sat, 18 Jun 2022 07:15:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38530 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233218AbiFRLNa (ORCPT ); Sat, 18 Jun 2022 07:13:30 -0400 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [IPv6:2a03:a000:7:0:5054:ff:fe1c:15ff]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 526BF15837 for ; Sat, 18 Jun 2022 04:13:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=GWT5w+pFhg/YK9TYYVCfAIZhGvME9EpV3zgbyYAfr9M=; b=bOPtrWeOiOsnuRRFIXrDo2oGpA FLVuezHlTUr+Jabwa2de/0uWY36SEHpR2/LDPcGCtAALuvPHOk7IJEcCfHhjc16eyQxzbc0WjA9Hm 8fy4v677mkLhq7yNfxviRebh5jRWdyX62trouzVpeg21UXI6B2OIRaip8yWoOk1M1cvmoa+5Uy14V Mi5IOsvM2BGDtrNyfrpOI6ff6CgOs8ZiBBc3/UCeyaUtoOoOoz2QyKkUwB98IzI8ufofnPVUNtJNL haZiee+jM1qWXojj17X7O5ldbVfgTsKbYj0rknhSD2r5t3ycs0VM4H3FVQdOTTyA+rijxsmGOzA/s SimzxtxA==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.95 #2 (Red Hat Linux)) id 1o2WOM-001ajf-Q4; Sat, 18 Jun 2022 11:13:27 +0000 Date: Sat, 18 Jun 2022 12:13:26 +0100 From: Al Viro To: linux-fsdevel@vger.kernel.org Cc: Christoph Hellwig , Jens Axboe , Matthew Wilcox Subject: Re: [PATCH 19/31] iov_iter: massage calling conventions for first_{iovec,bvec}_segment() Message-ID: References: <20220618053538.359065-1-viro@zeniv.linux.org.uk> <20220618053538.359065-20-viro@zeniv.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220618053538.359065-20-viro@zeniv.linux.org.uk> Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org [with braino fixed] >From 3893e9565ad55a8514f5f819545bf9df5a339c76 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 10 Jun 2022 22:19:25 -0400 Subject: [PATCH 19/31] iov_iter: massage calling conventions for first_{iovec,bvec}_segment() Pass maxsize by reference, return length via the same. And do not add offset to returned length. Callers adjusted... Signed-off-by: Al Viro --- lib/iov_iter.c | 50 +++++++++++++++++++++----------------------------- 1 file changed, 21 insertions(+), 29 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 8f1d63295f37..b789728678d2 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1307,25 +1307,22 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i, } static unsigned long found_ubuf_segment(unsigned long addr, - size_t len, - size_t *size, size_t *start) + size_t *start) { - len += (*start = addr % PAGE_SIZE); - *size = len; + *start = addr % PAGE_SIZE; return addr & PAGE_MASK; } /* must be done on non-empty ITER_UBUF or ITER_IOVEC one */ static unsigned long first_iovec_segment(const struct iov_iter *i, - size_t *size, size_t *start, - size_t maxsize) + size_t *size, size_t *start) { size_t skip; long k; if (iter_is_ubuf(i)) { unsigned long addr = (unsigned long)i->ubuf + i->iov_offset; - return found_ubuf_segment(addr, maxsize, size, start); + return found_ubuf_segment(addr, start); } for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) { @@ -1334,28 +1331,26 @@ static unsigned long first_iovec_segment(const struct iov_iter *i, if (unlikely(!len)) continue; - if (len > maxsize) - len = maxsize; - return found_ubuf_segment(addr, len, size, start); + if (*size > len) + *size = len; + return found_ubuf_segment(addr, start); } BUG(); // if it had been empty, we wouldn't get called } /* must be done on non-empty ITER_BVEC one */ static struct page *first_bvec_segment(const struct iov_iter *i, - size_t *size, size_t *start, - size_t maxsize) + size_t *size, size_t *start) { struct page *page; size_t skip = i->iov_offset, len; len = i->bvec->bv_len - skip; - if (len > maxsize) - len = maxsize; + if (*size > len) + *size = len; skip += i->bvec->bv_offset; page = i->bvec->bv_page + skip / PAGE_SIZE; - len += (*start = skip % PAGE_SIZE); - *size = len; + *start = skip % PAGE_SIZE; return page; } @@ -1363,7 +1358,6 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages, size_t maxsize, unsigned int maxpages, size_t *start) { - size_t len; int n, res; if (maxsize > i->count) @@ -1382,10 +1376,10 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, if (i->nofault) gup_flags |= FOLL_NOFAULT; - addr = first_iovec_segment(i, &len, start, maxsize); - if (len > maxpages * PAGE_SIZE) - len = maxpages * PAGE_SIZE; - n = DIV_ROUND_UP(len, PAGE_SIZE); + addr = first_iovec_segment(i, &maxsize, start); + n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE); + if (n > maxpages) + n = maxpages; if (*pages) { *pages = get_pages_array(n); if (!*pages) @@ -1394,18 +1388,16 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, res = get_user_pages_fast(addr, n, gup_flags, *pages); if (unlikely(res <= 0)) return res; - if (res < n) - len = res * PAGE_SIZE; - return len - *start; + return min_t(size_t, maxsize, res * PAGE_SIZE - *start); } if (iov_iter_is_bvec(i)) { struct page **p; struct page *page; - page = first_bvec_segment(i, &len, start, maxsize); - if (len > maxpages * PAGE_SIZE) - len = maxpages * PAGE_SIZE; - n = DIV_ROUND_UP(len, PAGE_SIZE); + page = first_bvec_segment(i, &maxsize, start); + n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE); + if (n > maxpages) + n = maxpages; p = *pages; if (!p) { *pages = p = get_pages_array(n); @@ -1414,7 +1406,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, } for (int k = 0; k < n; k++) get_page(*p++ = page++); - return len - *start; + return min_t(size_t, maxsize, n * PAGE_SIZE - *start); } if (iov_iter_is_pipe(i)) return pipe_get_pages(i, pages, maxsize, maxpages, start); -- 2.30.2