From c06306696f8368b08774e2a743dbc52d92a61693 Mon Sep 17 00:00:00 2001 From: Yang Shi Date: Thu, 18 Jul 2019 15:57:27 -0700 Subject: mm: thp: fix false negative of shmem vma's THP eligibility Commit 7635d9cbe832 ("mm, thp, proc: report THP eligibility for each vma") introduced THPeligible bit for processes' smaps. But, when checking the eligibility for shmem vma, __transparent_hugepage_enabled() is called to override the result from shmem_huge_enabled(). It may result in the anonymous vma's THP flag override shmem's. For example, running a simple test which create THP for shmem, but with anonymous THP disabled, when reading the process's smaps, it may show: 7fc92ec00000-7fc92f000000 rw-s 00000000 00:14 27764 /dev/shm/test Size: 4096 kB ... [snip] ... ShmemPmdMapped: 4096 kB ... [snip] ... THPeligible: 0 And, /proc/meminfo does show THP allocated and PMD mapped too: ShmemHugePages: 4096 kB ShmemPmdMapped: 4096 kB This doesn't make too much sense. The shmem objects should be treated separately from anonymous THP. Calling shmem_huge_enabled() with checking MMF_DISABLE_THP sounds good enough. And, we could skip stack and dax vma check since we already checked if the vma is shmem already. Also check if vma is suitable for THP by calling transhuge_vma_suitable(). And minor fix to smaps output format and documentation. Link: http://lkml.kernel.org/r/1560401041-32207-3-git-send-email-yang.shi@linux.alibaba.com Fixes: 7635d9cbe832 ("mm, thp, proc: report THP eligibility for each vma") Signed-off-by: Yang Shi Acked-by: Hugh Dickins Cc: Kirill A. Shutemov Cc: Michal Hocko Cc: Vlastimil Babka Cc: David Rientjes Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'fs/proc') diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 818cedbed95f..731642e0f5a0 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -832,7 +832,8 @@ static int show_smap(struct seq_file *m, void *v) __show_smap(m, &mss, false); - seq_printf(m, "THPeligible: %d\n", transparent_hugepage_enabled(vma)); + seq_printf(m, "THPeligible: %d\n", + transparent_hugepage_enabled(vma)); if (arch_pkeys_enabled()) seq_printf(m, "ProtectionKey: %8u\n", vma_pkey(vma)); -- cgit v1.2.3-59-g8ed1b