From: Hugh Dickins <hughd@google.com> stable inclusion from linux-4.19.197 commit 629ee482e0966c23ddc1abeebf71aa84ff8d3673 -------------------------------- [ Upstream commit 99fa8a48203d62b3743d866fc48ef6abaee682be ] 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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Note on stable backport: this commit made intervening cleanups in pmdp_huge_clear_flush() redundant: here it's rediffed to skip them. Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- mm/huge_memory.c | 27 ++++++++++++++++++--------- mm/pgtable-generic.c | 4 ++-- 2 files changed, 20 insertions(+), 11 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index e3f4bba22c82b..227ed32d3d40f 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2182,7 +2182,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, 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 @@ -2191,16 +2191,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, zap_deposited_table(mm, pmd); if (vma_is_dax(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 diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c index cf2af04b34b97..36770fcdc3582 100644 --- a/mm/pgtable-generic.c +++ b/mm/pgtable-generic.c @@ -125,8 +125,8 @@ pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address, { pmd_t pmd; VM_BUG_ON(address & ~HPAGE_PMD_MASK); - VM_BUG_ON((pmd_present(*pmdp) && !pmd_trans_huge(*pmdp) && - !pmd_devmap(*pmdp)) || !pmd_present(*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; -- 2.25.1