diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/hugetlb.c | 102 | ||||
| -rw-r--r-- | mm/memory.c | 2 | ||||
| -rw-r--r-- | mm/rmap.c | 100 | ||||
| -rw-r--r-- | mm/userfaultfd.c | 9 |
4 files changed, 168 insertions, 45 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index f44b79998ac2..d78504959df7 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4796,6 +4796,14 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, mmu_notifier_invalidate_range_start(&range); mmap_assert_write_locked(src); raw_write_seqcount_begin(&src->write_protect_seq); + } else { + /* + * For shared mappings the vma lock must be held before + * calling huge_pte_offset in the src vma. Otherwise, the + * returned ptep could go away if part of a shared pmd and + * another thread calls huge_pmd_unshare. + */ + hugetlb_vma_lock_read(src_vma); } last_addr_mask = hugetlb_mask_last_page(h); @@ -4942,6 +4950,8 @@ again: if (cow) { raw_write_seqcount_end(&src->write_protect_seq); mmu_notifier_invalidate_range_end(&range); + } else { + hugetlb_vma_unlock_read(src_vma); } return ret; @@ -5000,6 +5010,7 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma, mmu_notifier_invalidate_range_start(&range); last_addr_mask = hugetlb_mask_last_page(h); /* Prevent race with file truncation */ + hugetlb_vma_lock_write(vma); i_mmap_lock_write(mapping); for (; old_addr < old_end; old_addr += sz, new_addr += sz) { src_pte = huge_pte_offset(mm, old_addr, sz); @@ -5031,6 +5042,7 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma, flush_tlb_range(vma, old_end - len, old_end); mmu_notifier_invalidate_range_end(&range); i_mmap_unlock_write(mapping); + hugetlb_vma_unlock_write(vma); return len + old_addr - old_end; } @@ -5350,8 +5362,29 @@ retry_avoidcopy: * may get SIGKILLed if it later faults. */ if (outside_reserve) { + struct address_space *mapping = vma->vm_file->f_mapping; + pgoff_t idx; + u32 hash; + put_page(old_page); + /* + * Drop hugetlb_fault_mutex and vma_lock before + * unmapping. unmapping needs to hold vma_lock + * in write mode. Dropping vma_lock in read mode + * here is OK as COW mappings do not interact with + * PMD sharing. + * + * Reacquire both after unmap operation. + */ + idx = vma_hugecache_offset(h, vma, haddr); + hash = hugetlb_fault_mutex_hash(mapping, idx); + hugetlb_vma_unlock_read(vma); + mutex_unlock(&hugetlb_fault_mutex_table[hash]); + unmap_ref_private(mm, vma, old_page, haddr); + + mutex_lock(&hugetlb_fault_mutex_table[hash]); + hugetlb_vma_lock_read(vma); spin_lock(ptl); ptep = huge_pte_offset(mm, haddr, huge_page_size(h)); if (likely(ptep && @@ -5500,14 +5533,16 @@ static inline vm_fault_t hugetlb_handle_userfault(struct vm_area_struct *vma, }; /* - * hugetlb_fault_mutex and i_mmap_rwsem must be + * vma_lock and hugetlb_fault_mutex must be * dropped before handling userfault. Reacquire * after handling fault to make calling code simpler. */ + hugetlb_vma_unlock_read(vma); hash = hugetlb_fault_mutex_hash(mapping, idx); mutex_unlock(&hugetlb_fault_mutex_table[hash]); ret = handle_userfault(&vmf, reason); mutex_lock(&hugetlb_fault_mutex_table[hash]); + hugetlb_vma_lock_read(vma); return ret; } @@ -5741,6 +5776,11 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, ptep = huge_pte_offset(mm, haddr, huge_page_size(h)); if (ptep) { + /* + * Since we hold no locks, ptep could be stale. That is + * OK as we are only making decisions based on content and + * not actually modifying content here. + */ entry = huge_ptep_get(ptep); if (unlikely(is_hugetlb_entry_migration(entry))) { migration_entry_wait_huge(vma, ptep); @@ -5748,23 +5788,35 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, } else if (unlikely(is_hugetlb_entry_hwpoisoned(entry))) return VM_FAULT_HWPOISON_LARGE | VM_FAULT_SET_HINDEX(hstate_index(h)); - } else { - ptep = huge_pte_alloc(mm, vma, haddr, huge_page_size(h)); - if (!ptep) - return VM_FAULT_OOM; } - mapping = vma->vm_file->f_mapping; - idx = vma_hugecache_offset(h, vma, haddr); - /* * Serialize hugepage allocation and instantiation, so that we don't * get spurious allocation failures if two CPUs race to instantiate * the same page in the page cache. */ + mapping = vma->vm_file->f_mapping; + idx = vma_hugecache_offset(h, vma, haddr); hash = hugetlb_fault_mutex_hash(mapping, idx); mutex_lock(&hugetlb_fault_mutex_table[hash]); + /* + * Acquire vma lock before calling huge_pte_alloc and hold + * until finished with ptep. This prevents huge_pmd_unshare from + * being called elsewhere and making the ptep no longer valid. + * + * ptep could have already be assigned via huge_pte_offset. That + * is OK, as huge_pte_alloc will return the same value unless + * something has changed. + */ + hugetlb_vma_lock_read(vma); + ptep = huge_pte_alloc(mm, vma, haddr, huge_page_size(h)); + if (!ptep) { + hugetlb_vma_unlock_read(vma); + mutex_unlock(&hugetlb_fault_mutex_table[hash]); + return VM_FAULT_OOM; + } + entry = huge_ptep_get(ptep); /* PTE markers should be handled the same way as none pte */ if (huge_pte_none_mostly(entry)) { @@ -5825,6 +5877,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, unlock_page(pagecache_page); put_page(pagecache_page); } + hugetlb_vma_unlock_read(vma); mutex_unlock(&hugetlb_fault_mutex_table[hash]); return handle_userfault(&vmf, VM_UFFD_WP); } @@ -5868,6 +5921,7 @@ out_ptl: put_page(pagecache_page); } out_mutex: + hugetlb_vma_unlock_read(vma); mutex_unlock(&hugetlb_fault_mutex_table[hash]); /* * Generally it's safe to hold refcount during waiting page lock. But @@ -6330,8 +6384,9 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, flush_cache_range(vma, range.start, range.end); mmu_notifier_invalidate_range_start(&range); - last_addr_mask = hugetlb_mask_last_page(h); + hugetlb_vma_lock_write(vma); i_mmap_lock_write(vma->vm_file->f_mapping); + last_addr_mask = hugetlb_mask_last_page(h); for (; address < end; address += psize) { spinlock_t *ptl; ptep = huge_pte_offset(mm, address, psize); @@ -6430,6 +6485,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, * See Documentation/mm/mmu_notifier.rst */ i_mmap_unlock_write(vma->vm_file->f_mapping); + hugetlb_vma_unlock_write(vma); mmu_notifier_invalidate_range_end(&range); return pages << h->order; @@ -6931,6 +6987,7 @@ int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma, pud_t *pud = pud_offset(p4d, addr); i_mmap_assert_write_locked(vma->vm_file->f_mapping); + hugetlb_vma_assert_locked(vma); BUG_ON(page_count(virt_to_page(ptep)) == 0); if (page_count(virt_to_page(ptep)) == 1) return 0; @@ -6943,6 +7000,31 @@ int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma, #else /* !CONFIG_ARCH_WANT_HUGE_PMD_SHARE */ +void hugetlb_vma_lock_read(struct vm_area_struct *vma) +{ +} + +void hugetlb_vma_unlock_read(struct vm_area_struct *vma) +{ +} + +void hugetlb_vma_lock_write(struct vm_area_struct *vma) +{ +} + +void hugetlb_vma_unlock_write(struct vm_area_struct *vma) +{ +} + +int hugetlb_vma_trylock_write(struct vm_area_struct *vma) +{ + return 1; +} + +void hugetlb_vma_assert_locked(struct vm_area_struct *vma) +{ +} + void hugetlb_vma_lock_release(struct kref *kref) { } @@ -7325,6 +7407,7 @@ void hugetlb_unshare_all_pmds(struct vm_area_struct *vma) mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, start, end); mmu_notifier_invalidate_range_start(&range); + hugetlb_vma_lock_write(vma); i_mmap_lock_write(vma->vm_file->f_mapping); for (address = start; address < end; address += PUD_SIZE) { ptep = huge_pte_offset(mm, address, sz); @@ -7336,6 +7419,7 @@ void hugetlb_unshare_all_pmds(struct vm_area_struct *vma) } flush_hugetlb_tlb_range(vma, start, end); i_mmap_unlock_write(vma->vm_file->f_mapping); + hugetlb_vma_unlock_write(vma); /* * No need to call mmu_notifier_invalidate_range(), see * Documentation/mm/mmu_notifier.rst. diff --git a/mm/memory.c b/mm/memory.c index c01c12500169..b3ed17219d77 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1684,10 +1684,12 @@ static void unmap_single_vma(struct mmu_gather *tlb, if (vma->vm_file) { zap_flags_t zap_flags = details ? details->zap_flags : 0; + hugetlb_vma_lock_write(vma); i_mmap_lock_write(vma->vm_file->f_mapping); __unmap_hugepage_range_final(tlb, vma, start, end, NULL, zap_flags); i_mmap_unlock_write(vma->vm_file->f_mapping); + hugetlb_vma_unlock_write(vma); } } else unmap_page_range(tlb, vma, start, end, details); diff --git a/mm/rmap.c b/mm/rmap.c index 0e179c823e0a..b6743c2b8b5f 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1551,24 +1551,39 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, * To call huge_pmd_unshare, i_mmap_rwsem must be * held in write mode. Caller needs to explicitly * do this outside rmap routines. + * + * We also must hold hugetlb vma_lock in write mode. + * Lock order dictates acquiring vma_lock BEFORE + * i_mmap_rwsem. We can only try lock here and fail + * if unsuccessful. */ - VM_BUG_ON(!anon && !(flags & TTU_RMAP_LOCKED)); - if (!anon && huge_pmd_unshare(mm, vma, address, pvmw.pte)) { - flush_tlb_range(vma, range.start, range.end); - mmu_notifier_invalidate_range(mm, range.start, - range.end); - - /* - * The ref count of the PMD page was dropped - * which is part of the way map counting - * is done for shared PMDs. Return 'true' - * here. When there is no other sharing, - * huge_pmd_unshare returns false and we will - * unmap the actual page and drop map count - * to zero. - */ - page_vma_mapped_walk_done(&pvmw); - break; + if (!anon) { + VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); + if (!hugetlb_vma_trylock_write(vma)) { + page_vma_mapped_walk_done(&pvmw); + ret = false; + break; + } + if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) { + hugetlb_vma_unlock_write(vma); + flush_tlb_range(vma, + range.start, range.end); + mmu_notifier_invalidate_range(mm, + range.start, range.end); + /* + * The ref count of the PMD page was + * dropped which is part of the way map + * counting is done for shared PMDs. + * Return 'true' here. When there is + * no other sharing, huge_pmd_unshare + * returns false and we will unmap the + * actual page and drop map count + * to zero. + */ + page_vma_mapped_walk_done(&pvmw); + break; + } + hugetlb_vma_unlock_write(vma); } pteval = huge_ptep_clear_flush(vma, address, pvmw.pte); } else { @@ -1926,26 +1941,41 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, * To call huge_pmd_unshare, i_mmap_rwsem must be * held in write mode. Caller needs to explicitly * do this outside rmap routines. + * + * We also must hold hugetlb vma_lock in write mode. + * Lock order dictates acquiring vma_lock BEFORE + * i_mmap_rwsem. We can only try lock here and + * fail if unsuccessful. */ - VM_BUG_ON(!anon && !(flags & TTU_RMAP_LOCKED)); - if (!anon && huge_pmd_unshare(mm, vma, address, pvmw.pte)) { - flush_tlb_range(vma, range.start, range.end); - mmu_notifier_invalidate_range(mm, range.start, - range.end); - - /* - * The ref count of the PMD page was dropped - * which is part of the way map counting - * is done for shared PMDs. Return 'true' - * here. When there is no other sharing, - * huge_pmd_unshare returns false and we will - * unmap the actual page and drop map count - * to zero. - */ - page_vma_mapped_walk_done(&pvmw); - break; + if (!anon) { + VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); + if (!hugetlb_vma_trylock_write(vma)) { + page_vma_mapped_walk_done(&pvmw); + ret = false; + break; + } + if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) { + hugetlb_vma_unlock_write(vma); + flush_tlb_range(vma, + range.start, range.end); + mmu_notifier_invalidate_range(mm, + range.start, range.end); + + /* + * The ref count of the PMD page was + * dropped which is part of the way map + * counting is done for shared PMDs. + * Return 'true' here. When there is + * no other sharing, huge_pmd_unshare + * returns false and we will unmap the + * actual page and drop map count + * to zero. + */ + page_vma_mapped_walk_done(&pvmw); + break; + } + hugetlb_vma_unlock_write(vma); } - /* Nuke the hugetlb page table entry */ pteval = huge_ptep_clear_flush(vma, address, pvmw.pte); } else { diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 0fdbd2c05587..e24e8a47ce8a 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -379,16 +379,21 @@ retry: BUG_ON(dst_addr >= dst_start + len); /* - * Serialize via hugetlb_fault_mutex. + * Serialize via vma_lock and hugetlb_fault_mutex. + * vma_lock ensures the dst_pte remains valid even + * in the case of shared pmds. fault mutex prevents + * races with other faulting threads. */ idx = linear_page_index(dst_vma, dst_addr); mapping = dst_vma->vm_file->f_mapping; hash = hugetlb_fault_mutex_hash(mapping, idx); mutex_lock(&hugetlb_fault_mutex_table[hash]); + hugetlb_vma_lock_read(dst_vma); err = -ENOMEM; dst_pte = huge_pte_alloc(dst_mm, dst_vma, dst_addr, vma_hpagesize); if (!dst_pte) { + hugetlb_vma_unlock_read(dst_vma); mutex_unlock(&hugetlb_fault_mutex_table[hash]); goto out_unlock; } @@ -396,6 +401,7 @@ retry: if (mode != MCOPY_ATOMIC_CONTINUE && !huge_pte_none_mostly(huge_ptep_get(dst_pte))) { err = -EEXIST; + hugetlb_vma_unlock_read(dst_vma); mutex_unlock(&hugetlb_fault_mutex_table[hash]); goto out_unlock; } @@ -404,6 +410,7 @@ retry: dst_addr, src_addr, mode, &page, wp_copy); + hugetlb_vma_unlock_read(dst_vma); mutex_unlock(&hugetlb_fault_mutex_table[hash]); cond_resched(); |