From: Peter Xu peterx@redhat.com
commit 5fc7a5f6fd04bc18f309d9f979b32ef7d1d0a997 upstream.
Patch series "mm/uffd: Misc fix for uffd-wp and one more test".
This series tries to fix some corner case bugs for uffd-wp on either thp or fork(). Then it introduced a new test with pagemap/pageout.
Patch layout:
Patch 1: cleanup for THP, it'll slightly simplify the follow up patches Patch 2-4: misc fixes for uffd-wp here and there; please refer to each patch Patch 5: add pagemap support for uffd-wp Patch 6: add pagemap/pageout test for uffd-wp
The last test introduced can also verify some of the fixes in previous patches, as the test will fail without the fixes. However it's not easy to verify all the changes in patch 2-4, but hopefully they can still be properly reviewed.
Note that if considering the ongoing uffd-wp shmem & hugetlbfs work, patch 5 will be incomplete as it's missing e.g. hugetlbfs part or the special swap pte detection. However that's not needed in this series, and since that series is still during review, this series does not depend on that one (the last test only runs with anonymous memory, not file-backed). So this series can be merged even before that series.
This patch (of 6):
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.
Link: https://lkml.kernel.org/r/20210428225030.9708-1-peterx@redhat.com Link: https://lkml.kernel.org/r/20210428225030.9708-2-peterx@redhat.com Signed-off-by: Peter Xu peterx@redhat.com Cc: Kirill A. Shutemov kirill@shutemov.name Cc: Mike Kravetz mike.kravetz@oracle.com, peterx@redhat.com Cc: Mike Rapoport rppt@linux.vnet.ibm.com Cc: Axel Rasmussen axelrasmussen@google.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: Hugh Dickins hughd@google.com Cc: Jerome Glisse jglisse@redhat.com Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: Brian Geffon bgeffon@google.com Cc: "Dr . David Alan Gilbert" dgilbert@redhat.com Cc: Joe Perches joe@perches.com Cc: Lokesh Gidra lokeshgidra@google.com Cc: Mina Almasry almasrymina@google.com Cc: Oliver Upton oupton@google.com Cc: Shaohua Li shli@fb.com Cc: Shuah Khan shuah@kernel.org Cc: Stephen Rothwell sfr@canb.auug.org.au Cc: Wang Qing wangqing@vivo.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/huge_memory.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-)
--- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1088,17 +1088,13 @@ int copy_huge_pmd(struct mm_struct *dst_ * 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); @@ -1122,6 +1118,7 @@ int copy_huge_pmd(struct mm_struct *dst_ 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);