On 07.06.24 11:33, Alex Shi wrote:
On 6/5/24 5:56 PM, David Hildenbrand wrote:
On 05.06.24 11:53, alexs@xxxxxxxxxx wrote:
From: "Alex Shi (tencent)" <alexs@xxxxxxxxxx>
We do vma_set_anonyous in do_mmap(), and then vma_is_anonymous()
checking workable, use it as a extra check since ksm only care anonymous
pages.
Signed-off-by: Alex Shi (tencent) <alexs@xxxxxxxxxx>
---
mm/ksm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/ksm.c b/mm/ksm.c
index f5138f43f0d2..088bce39cd33 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -742,7 +742,8 @@ static struct vm_area_struct *find_mergeable_vma(struct mm_struct *mm,
if (ksm_test_exit(mm))
return NULL;
vma = vma_lookup(mm, addr);
- if (!vma || !(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
+ if (!vma || !(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma ||
+ !vma_is_anonymous(vma))
Doesn't KSM also apply to COW'ed pages in !anon mappings? At least that's what I recall.
I didn't a evidence for this. :(
In write_protect_page(), "PageAnonExclusive(&folio->page);" has a "VM_BUG_ON_PGFLAGS(!PageAnon(page), page);"
So is this hints the vma also need to be anonymous one?
vma_is_anonymous(vma) is restricted to anonymous folios and the shared
zeropage, but other VMAs (MAP_PRIVATE file-backed VMAs) can contain
anonymous folios as well.
--
Cheers,
David / dhildenb
