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authorYang Shi <yang.shi@linux.alibaba.com>2019-07-19 01:57:27 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-19 03:08:06 +0300
commitc06306696f8368b08774e2a743dbc52d92a61693 (patch)
tree2aecc465f56501c3a42457f43e3b33b97598b50f /mm/huge_memory.c
parent43675e6fbbeadca90c6c5031557ff95e217e6d2f (diff)
downloadlinux-c06306696f8368b08774e2a743dbc52d92a61693.tar.xz
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 <yang.shi@linux.alibaba.com> Acked-by: Hugh Dickins <hughd@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: David Rientjes <rientjes@google.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
-rw-r--r--mm/huge_memory.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 782dd1446a3e..1334ede667a8 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -63,10 +63,15 @@ struct page *huge_zero_page __read_mostly;
bool transparent_hugepage_enabled(struct vm_area_struct *vma)
{
+ /* The addr is used to check if the vma size fits */
+ unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE;
+
+ if (!transhuge_vma_suitable(vma, addr))
+ return false;
if (vma_is_anonymous(vma))
return __transparent_hugepage_enabled(vma);
- if (vma_is_shmem(vma) && shmem_huge_enabled(vma))
- return __transparent_hugepage_enabled(vma);
+ if (vma_is_shmem(vma))
+ return shmem_huge_enabled(vma);
return false;
}