@@ -2044,7 +2044,7 @@ static void __split_huge_pmd_locked(stru
count_vm_event(THP_SPLIT_PMD);
if (!vma_is_anonymous(vma)) {
- _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
+ old_pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
/*
* We are going to unmap this huge page. So
* just go ahead and zap it
@@ -2053,16 +2053,25 @@ static void __split_huge_pmd_locked(stru
zap_deposited_table(mm, pmd);
if (vma_is_special_huge(vma))
return;
- page = pmd_page(_pmd);
- if (!PageDirty(page) && pmd_dirty(_pmd))
- set_page_dirty(page);
- if (!PageReferenced(page) && pmd_young(_pmd))
- SetPageReferenced(page);
- page_remove_rmap(page, true);
- put_page(page);
+ if (unlikely(is_pmd_migration_entry(old_pmd))) {
+ swp_entry_t entry;
+
+ entry = pmd_to_swp_entry(old_pmd);
+ page = migration_entry_to_page(entry);
+ } else {
+ page = pmd_page(old_pmd);
+ if (!PageDirty(page) && pmd_dirty(old_pmd))
+ set_page_dirty(page);
+ if (!PageReferenced(page) && pmd_young(old_pmd))
+ SetPageReferenced(page);
+ page_remove_rmap(page, true);
+ put_page(page);
+ }
add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
return;
- } else if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) {
+ }
+
+ if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) {
/*
* FIXME: Do we want to invalidate secondary mmu by calling
* mmu_notifier_invalidate_range() see comments below inside
@@ -135,9 +135,8 @@ pmd_t pmdp_huge_clear_flush(struct vm_ar
{
pmd_t pmd;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
- VM_BUG_ON(!pmd_present(*pmdp));
- /* Below assumes pmd_present() is true */
- VM_BUG_ON(!pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
+ VM_BUG_ON(pmd_present(*pmdp) && !pmd_trans_huge(*pmdp) &&
+ !pmd_devmap(*pmdp));
pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);
flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
return pmd;
The patch titled Subject: mm/thp: fix __split_huge_pmd_locked() on shmem migration entry has been removed from the -mm tree. Its filename was mm-thp-fix-__split_huge_pmd_locked-on-shmem-migration-entry.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Hugh Dickins <hughd@google.com> Subject: mm/thp: fix __split_huge_pmd_locked() on shmem migration entry Patch series "mm/thp: fix THP splitting unmap BUGs and related", v10. Here is v2 batch of long-standing THP bug fixes that I had not got around to sending before, but prompted now by Wang Yugui's report https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/ Wang Yugui has tested a rollup of these fixes applied to 5.10.39, and they have done no harm, but have *not* fixed that issue: something more is needed and I have no idea of what. This patch (of 7): Stressing huge tmpfs page migration racing hole punch often crashed on the VM_BUG_ON(!pmd_present) in pmdp_huge_clear_flush(), with DEBUG_VM=y kernel; or shortly afterwards, on a bad dereference in __split_huge_pmd_locked() when DEBUG_VM=n. They forgot to allow for pmd migration entries in the non-anonymous case. Full disclosure: those particular experiments were on a kernel with more relaxed mmap_lock and i_mmap_rwsem locking, and were not repeated on the vanilla kernel: it is conceivable that stricter locking happens to avoid those cases, or makes them less likely; but __split_huge_pmd_locked() already allowed for pmd migration entries when handling anonymous THPs, so this commit brings the shmem and file THP handling into line. And while there: use old_pmd rather than _pmd, as in the following blocks; and make it clearer to the eye that the !vma_is_anonymous() block is self-contained, making an early return after accounting for unmapping. Link: https://lkml.kernel.org/r/af88612-1473-2eaa-903-8d1a448b26@google.com Link: https://lkml.kernel.org/r/dd221a99-efb3-cd1d-6256-7e646af29314@google.com Fixes: e71769ae5260 ("mm: enable thp migration for shmem thp") Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Wang Yugui <wangyugui@e16-tech.com> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Zi Yan <ziy@nvidia.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Jue Wang <juew@google.com> Cc: Peter Xu <peterx@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Shakeel Butt <shakeelb@google.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- mm/huge_memory.c | 27 ++++++++++++++++++--------- mm/pgtable-generic.c | 5 ++--- 2 files changed, 20 insertions(+), 12 deletions(-)