On Tue, 14 Apr 2020, Andrew Morton wrote: > On Tue, 14 Apr 2020 07:18:01 -0700 Randy Dunlap wrote: > > On 4/13/20 7:39 PM, Stephen Rothwell wrote: > > > Hi all, > > > > > > Changes since 20200413: > > > > > > New tree: mhi > > > > > > My fixes tree contains: > > > > > > 6b038bdcd3d1 sh: mm: Fix build error > > > > > > Non-merge commits (relative to Linus' tree): 1154 > > > 1160 files changed, 31764 insertions(+), 13498 deletions(-) > > > > > > ---------------------------------------------------------------------------- > > > > on x86_64: > > # CONFIG_TRANSPARENT_HUGEPAGE is not set > > Thanks. hm, this took a long time to be discovered. > > > 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 ‘shmem_undo_range’: ... > > ../mm/shmem.c:961:26: note: in expansion of macro ‘HPAGE_PMD_NR’ > > round_up(start, HPAGE_PMD_NR)) > > ^~~~~~~~~~~~ > > That's > if (index < > round_up(start, HPAGE_PMD_NR)) > start = index + 1; > > 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=y: 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 punching 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 2020-04-11 12:58:26.415524805 -0700 +++ linux/mm/shmem.c 2020-04-14 23:20:25.517656174 -0700 @@ -952,7 +952,7 @@ static void shmem_undo_range(struct inod VM_BUG_ON_PAGE(PageWriteback(page), page); if (shmem_punch_compound(page, start, end)) truncate_inode_page(mapping, page); - else { + else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { /* Wipe the page and don't get stuck */ clear_highpage(page); flush_dcache_page(page);