Kirill A. Shutemov wrote:
> As with rmap, with new refcounting we cannot rely on PageTransHuge() to
> check if we need to charge size of huge page form the cgroup. We need to
> get information from caller to know whether it was mapped with PMD or
> PTE.
>
> We do uncharge when last reference on the page gone. At that point if we
> see PageTransHuge() it means we need to unchange whole huge page.
>
> The tricky part is partial unmap -- when we try to unmap part of huge
> page. We don't do a special handing of this situation, meaning we don't
> uncharge the part of huge page unless last user is gone or
> split_huge_page() is triggered. In case of cgroup memory pressure
> happens the partial unmapped page will be split through shrinker. This
> should be good enough.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Tested-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
checkpatch fixlet:
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 6dd365d1c488..117bedd02db2 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1103,8 +1103,8 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
if (unlikely(!page))
return -ENOMEM;
- if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL, &memcg, false))
- {
+ if (mem_cgroup_try_charge(page, vma->vm_mm, GFP_KERNEL,
+ &memcg, false)) {
ret = -ENOMEM;
goto out_nolock;
}
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