| Message ID | 20210428225030.9708-2-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/uffd: Misc fix for uffd-wp and one more test | expand |
On 29.04.21 00:50, Peter Xu wrote: > Huge zero page is handled in a special path in copy_huge_pmd(), however it > should share most codes with a normal thp page. Trying to share more code with > it by removing the special path. The only leftover so far is the huge zero > page refcounting (mm_get_huge_zero_page()), because that's separately done with > a global counter. > > This prepares for a future patch to modify the huge pmd to be installed, so > that we don't need to duplicate it explicitly into huge zero page case too. > > Cc: Kirill A. Shutemov <kirill@shutemov.name> > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > mm/huge_memory.c | 9 +++------ > 1 file changed, 3 insertions(+), 6 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 98456017744d6..22bf2d0fff79b 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1076,17 +1076,13 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, > * a page table. > */ > if (is_huge_zero_pmd(pmd)) { > - struct page *zero_page; > /* > * get_huge_zero_page() will never allocate a new page here, > * since we already have a zero page to copy. It just takes a > * reference. > */ > - zero_page = mm_get_huge_zero_page(dst_mm); > - set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, > - zero_page); > - ret = 0; > - goto out_unlock; > + mm_get_huge_zero_page(dst_mm); > + goto out_zero_page; > } > > src_page = pmd_page(pmd); > @@ -1110,6 +1106,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, > get_page(src_page); > page_dup_rmap(src_page, true); > add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); > +out_zero_page: > mm_inc_nr_ptes(dst_mm); > pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); > > AFAIKs, the only change is that we're now doing an additional pmdp_set_wrprotect(src_mm, addr, src_pmd) pmd = pmd_mkold(pmd_wrprotect(pmd)); But as we are copying the zeropage, it should already be write-protected, so no effective change. LGTM
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 98456017744d6..22bf2d0fff79b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1076,17 +1076,13 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, * a page table. */ if (is_huge_zero_pmd(pmd)) { - struct page *zero_page; /* * get_huge_zero_page() will never allocate a new page here, * since we already have a zero page to copy. It just takes a * reference. */ - zero_page = mm_get_huge_zero_page(dst_mm); - set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, - zero_page); - ret = 0; - goto out_unlock; + mm_get_huge_zero_page(dst_mm); + goto out_zero_page; } src_page = pmd_page(pmd); @@ -1110,6 +1106,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, get_page(src_page); page_dup_rmap(src_page, true); add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); +out_zero_page: mm_inc_nr_ptes(dst_mm); pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
Huge zero page is handled in a special path in copy_huge_pmd(), however it should share most codes with a normal thp page. Trying to share more code with it by removing the special path. The only leftover so far is the huge zero page refcounting (mm_get_huge_zero_page()), because that's separately done with a global counter. This prepares for a future patch to modify the huge pmd to be installed, so that we don't need to duplicate it explicitly into huge zero page case too. Cc: Kirill A. Shutemov <kirill@shutemov.name> Signed-off-by: Peter Xu <peterx@redhat.com> --- mm/huge_memory.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-)