| Message ID | 20220131160254.43211-5-songmuchun@bytedance.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Fix some cache flush bugs | expand |
Cc: Matthew On 1/31/22 08:02, Muchun Song wrote: > folio_copy() will copy the data from one page to the target page, then > the target page will be mapped to the user space address, which might > have an alias issue with the kernel address used to copy the data from > the page to. Fix this issue by flushing dcache but not use > flush_dcache_folio() since it is not backportable. > > Fixes: 8cc5fcbb5be8 ("mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY") > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > --- > mm/hugetlb.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index a1baa198519a..f1f1ab31dc8a 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -5804,6 +5804,8 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, > goto out; > } > } else { > + int i, nr; > + > if (vm_shared && > hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) { > put_page(*pagep); > @@ -5819,6 +5821,9 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, > goto out; > } > folio_copy(page_folio(page), page_folio(*pagep)); What if we changed that folio_copy() to? copy_user_huge_page(page, *pagep, dst_addr, dst_vma, pages_per_huge_page(h)); Seems like that would take care of the flush_dcache_page and it would be backportable. Of course, Matthew may hate the idea. Not sure if there are any plans to convert copy_user_huge_page to use folio type as it has some special hinting logic.
On Wed, Feb 2, 2022 at 6:24 AM Mike Kravetz <mike.kravetz@oracle.com> wrote: > > Cc: Matthew > > On 1/31/22 08:02, Muchun Song wrote: > > folio_copy() will copy the data from one page to the target page, then > > the target page will be mapped to the user space address, which might > > have an alias issue with the kernel address used to copy the data from > > the page to. Fix this issue by flushing dcache but not use > > flush_dcache_folio() since it is not backportable. > > > > Fixes: 8cc5fcbb5be8 ("mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY") > > Signed-off-by: Muchun Song <songmuchun@bytedance.com> > > --- > > mm/hugetlb.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index a1baa198519a..f1f1ab31dc8a 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -5804,6 +5804,8 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, > > goto out; > > } > > } else { > > + int i, nr; > > + > > if (vm_shared && > > hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) { > > put_page(*pagep); > > @@ -5819,6 +5821,9 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, > > goto out; > > } > > folio_copy(page_folio(page), page_folio(*pagep)); > > What if we changed that folio_copy() to? > > copy_user_huge_page(page, *pagep, dst_addr, dst_vma, > pages_per_huge_page(h)); > > Seems like that would take care of the flush_dcache_page and it would be > backportable. Agree. I also can replace folio_copy() with copy_user_huge_page(). > > Of course, Matthew may hate the idea. Not sure if there are any plans to > convert copy_user_huge_page to use folio type as it has some special hinting > logic.
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a1baa198519a..f1f1ab31dc8a 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5804,6 +5804,8 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, goto out; } } else { + int i, nr; + if (vm_shared && hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) { put_page(*pagep); @@ -5819,6 +5821,9 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, goto out; } folio_copy(page_folio(page), page_folio(*pagep)); + nr = compound_nr(page); + for (i = 0; i < nr; i++) + flush_dcache_page(page + i); put_page(*pagep); *pagep = NULL; }
folio_copy() will copy the data from one page to the target page, then the target page will be mapped to the user space address, which might have an alias issue with the kernel address used to copy the data from the page to. Fix this issue by flushing dcache but not use flush_dcache_folio() since it is not backportable. Fixes: 8cc5fcbb5be8 ("mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY") Signed-off-by: Muchun Song <songmuchun@bytedance.com> --- mm/hugetlb.c | 5 +++++ 1 file changed, 5 insertions(+)