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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 10sm6056280oin.42.2020.04.14.23.54.48 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Tue, 14 Apr 2020 23:54:49 -0700 (PDT) Date: Tue, 14 Apr 2020 23:54:29 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Andrew Morton cc: Randy Dunlap , Stephen Rothwell , Linux Next Mailing List , Linux Kernel Mailing List , Linux MM , Hugh Dickins Subject: Re: linux-next: Tree for Apr 14 (mm/shmem.c) In-Reply-To: <20200414182430.c5af29ddb1735f5fd0083983@linux-foundation.org> Message-ID: References: <20200414123900.4f97a83f@canb.auug.org.au> <200c608a-8159-18ce-b44e-cad2022e23e2@infradead.org> <20200414182430.c5af29ddb1735f5fd0083983@linux-foundation.org> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="0-6116103-1586933689=:10035" 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: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --0-6116103-1586933689=:10035 Content-Type: TEXT/PLAIN; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE On Tue, 14 Apr 2020, Andrew Morton wrote: > On Tue, 14 Apr 2020 07:18:01 -0700 Randy Dunlap w= rote: > > On 4/13/20 7:39 PM, Stephen Rothwell wrote: > > > Hi all, > > >=20 > > > Changes since 20200413: > > >=20 > > > New tree: mhi > > >=20 > > > My fixes tree contains: > > >=20 > > > 6b038bdcd3d1 sh: mm: Fix build error > > >=20 > > > Non-merge commits (relative to Linus' tree): 1154 > > > 1160 files changed, 31764 insertions(+), 13498 deletions(-) > > >=20 > > > ---------------------------------------------------------------------= ------- > >=20 > > on x86_64: > > # CONFIG_TRANSPARENT_HUGEPAGE is not set >=20 > Thanks. hm, this took a long time to be discovered. >=20 > > In file included from ../include/linux/export.h:43:0, > > from ../include/linux/linkage.h:7, > > from ../include/linux/fs.h:5, > > from ../mm/shmem.c:24: > > ../mm/shmem.c: In function =E2=80=98shmem_undo_range=E2=80=99: =2E.. > > ../mm/shmem.c:961:26: note: in expansion of macro =E2=80=98HPAGE_PMD_NR= =E2=80=99 > > round_up(start, HPAGE_PMD_NR)) > > ^~~~~~~~~~~~ >=20 > That's > =09=09=09=09=09if (index < > =09=09=09=09=09 round_up(start, HPAGE_PMD_NR)) > =09=09=09=09=09=09start =3D index + 1; >=20 > from Hugh's 71725ed10c40696 ("mm: huge tmpfs: try to split_huge_page() > when punching hole"). Sorry about that. Yes, odd that it should only hit now: the false PageTransCompound in shmem_punch_compound() has always been good enough to handle it for me, but maybe Randy is trying a less able compiler, or maybe unrelated changes in linux-next have just made it harder for the compiler to see the optimization. I hope the patch below fixes it? [PATCH] mm/shmem: fix build without THP Some optimizers don't notice that shmem_punch_compound() is always true (PageTransCompound() being false) without CONFIG_TRANSPARENT_HUGEPAGE=3Dy: use IS_ENABLED to help them to avoid the BUILD_BUG inside HPAGE_PMD_NR. Fixes: 71725ed10c40 ("mm: huge tmpfs: try to split_huge_page() when punchin= g hole") Reported-by: Randy Dunlap Signed-off-by: Hugh Dickins --- mm/shmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- 5.7-rc1/mm/shmem.c=092020-04-11 12:58:26.415524805 -0700 +++ linux/mm/shmem.c=092020-04-14 23:20:25.517656174 -0700 @@ -952,7 +952,7 @@ static void shmem_undo_range(struct inod =09=09=09=09VM_BUG_ON_PAGE(PageWriteback(page), page); =09=09=09=09if (shmem_punch_compound(page, start, end)) =09=09=09=09=09truncate_inode_page(mapping, page); -=09=09=09=09else { +=09=09=09=09else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { =09=09=09=09=09/* Wipe the page and don't get stuck */ =09=09=09=09=09clear_highpage(page); =09=09=09=09=09flush_dcache_page(page); --0-6116103-1586933689=:10035--