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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A0498CA1013 for ; Fri, 5 Sep 2025 23:01:23 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 1C3F410EC62; Fri, 5 Sep 2025 23:01:23 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="FKhh4N0Y"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id D5AEB10EC62; Fri, 5 Sep 2025 23:01:21 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id CBCC2601AA; Fri, 5 Sep 2025 23:01:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2CEDC4CEF1; Fri, 5 Sep 2025 23:01:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1757113280; bh=+lhopyxIHPkimkHLqjBagKsowbxPduHdhl1alB5XIHw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FKhh4N0YC7rktiPdXEfXclWanEDKYne9TN6cdcuCjqPCtcq4Rn0r96yLuECJbiw+4 LjwCnjQtLBAm0edveUnCZZYiNonj/7aqKLJr2wGtnUHH+scBK/7r7JUigttXLAScDm pXeFnpIPvL1/rZKX9LdznwwDYBYkDL4/X0Q74Dlpx/NmySnEYO46ImCPWzvWXVlUfn 7nKQ1fERSefzbF0N9pUOtT2Ew99OpHStRZ+01KHKpecJw2kFIukduhp+K3hQulq8o0 47VhyxuU+d72ralUlgkhIgcgxiZyD9aQX9YFUuu3Ep7hq8BTDKfbNp6DFssdME8qWg uTEId8/MJZDQg== Date: Fri, 5 Sep 2025 16:00:06 -0700 From: Eric Biggers To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Alexander Potapenko , Andrew Morton , Brendan Jackman , Christoph Lameter , Dennis Zhou , Dmitry Vyukov , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, iommu@lists.linux.dev, io-uring@vger.kernel.org, Jason Gunthorpe , Jens Axboe , Johannes Weiner , John Hubbard , kasan-dev@googlegroups.com, kvm@vger.kernel.org, "Liam R. Howlett" , Linus Torvalds , linux-arm-kernel@axis.com, linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org, linux-ide@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mmc@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, Lorenzo Stoakes , Marco Elver , Marek Szyprowski , Michal Hocko , Mike Rapoport , Muchun Song , netdev@vger.kernel.org, Oscar Salvador , Peter Xu , Robin Murphy , Suren Baghdasaryan , Tejun Heo , virtualization@lists.linux.dev, Vlastimil Babka , wireguard@lists.zx2c4.com, x86@kernel.org, Zi Yan Subject: Re: [PATCH v2 19/37] mm/gup: remove record_subpages() Message-ID: <20250905230006.GA1776@sol> References: <20250901150359.867252-1-david@redhat.com> <20250901150359.867252-20-david@redhat.com> <5090355d-546a-4d06-99e1-064354d156b5@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5090355d-546a-4d06-99e1-064354d156b5@redhat.com> X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Fri, Sep 05, 2025 at 08:41:23AM +0200, David Hildenbrand wrote: > On 01.09.25 17:03, David Hildenbrand wrote: > > We can just cleanup the code by calculating the #refs earlier, > > so we can just inline what remains of record_subpages(). > > > > Calculate the number of references/pages ahead of times, and record them > > only once all our tests passed. > > > > Signed-off-by: David Hildenbrand > > --- > > mm/gup.c | 25 ++++++++----------------- > > 1 file changed, 8 insertions(+), 17 deletions(-) > > > > diff --git a/mm/gup.c b/mm/gup.c > > index c10cd969c1a3b..f0f4d1a68e094 100644 > > --- a/mm/gup.c > > +++ b/mm/gup.c > > @@ -484,19 +484,6 @@ static inline void mm_set_has_pinned_flag(struct mm_struct *mm) > > #ifdef CONFIG_MMU > > #ifdef CONFIG_HAVE_GUP_FAST > > -static int record_subpages(struct page *page, unsigned long sz, > > - unsigned long addr, unsigned long end, > > - struct page **pages) > > -{ > > - int nr; > > - > > - page += (addr & (sz - 1)) >> PAGE_SHIFT; > > - for (nr = 0; addr != end; nr++, addr += PAGE_SIZE) > > - pages[nr] = page++; > > - > > - return nr; > > -} > > - > > /** > > * try_grab_folio_fast() - Attempt to get or pin a folio in fast path. > > * @page: pointer to page to be grabbed > > @@ -2967,8 +2954,8 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr, > > if (pmd_special(orig)) > > return 0; > > - page = pmd_page(orig); > > - refs = record_subpages(page, PMD_SIZE, addr, end, pages + *nr); > > + refs = (end - addr) >> PAGE_SHIFT; > > + page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); > > folio = try_grab_folio_fast(page, refs, flags); > > if (!folio) > > @@ -2989,6 +2976,8 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr, > > } > > *nr += refs; > > + for (; refs; refs--) > > + *(pages++) = page++; > > folio_set_referenced(folio); > > return 1; > > } > > @@ -3007,8 +2996,8 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr, > > if (pud_special(orig)) > > return 0; > > - page = pud_page(orig); > > - refs = record_subpages(page, PUD_SIZE, addr, end, pages + *nr); > > + refs = (end - addr) >> PAGE_SHIFT; > > + page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); > > folio = try_grab_folio_fast(page, refs, flags); > > if (!folio) > > @@ -3030,6 +3019,8 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr, > > } > > *nr += refs; > > + for (; refs; refs--) > > + *(pages++) = page++; > > folio_set_referenced(folio); > > return 1; > > } > > Okay, this code is nasty. We should rework this code to just return the nr and receive a the proper > pages pointer, getting rid of the "*nr" parameter. > > For the time being, the following should do the trick: > > commit bfd07c995814354f6b66c5b6a72e96a7aa9fb73b (HEAD -> nth_page) > Author: David Hildenbrand > Date: Fri Sep 5 08:38:43 2025 +0200 > > fixup: mm/gup: remove record_subpages() > pages is not adjusted by the caller, but idnexed by existing *nr. > Signed-off-by: David Hildenbrand > > diff --git a/mm/gup.c b/mm/gup.c > index 010fe56f6e132..22420f2069ee1 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -2981,6 +2981,7 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr, > return 0; > } > + pages += *nr; > *nr += refs; > for (; refs; refs--) > *(pages++) = page++; > @@ -3024,6 +3025,7 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr, > return 0; > } > + pages += *nr; > *nr += refs; > for (; refs; refs--) > *(pages++) = page++; Can this get folded in soon? This bug is causing crashes in AF_ALG too. Thanks, - Eric