diff options
Diffstat (limited to 'mm/hugetlb.c')
| -rw-r--r-- | mm/hugetlb.c | 133 |
1 files changed, 82 insertions, 51 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a80832487981..e37efd5d8318 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3238,24 +3238,35 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, struct page *ptepage; unsigned long addr; int cow; + struct address_space *mapping = vma->vm_file->f_mapping; struct hstate *h = hstate_vma(vma); unsigned long sz = huge_page_size(h); - unsigned long mmun_start; /* For mmu_notifiers */ - unsigned long mmun_end; /* For mmu_notifiers */ + struct mmu_notifier_range range; int ret = 0; cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; - mmun_start = vma->vm_start; - mmun_end = vma->vm_end; - if (cow) - mmu_notifier_invalidate_range_start(src, mmun_start, mmun_end); + if (cow) { + mmu_notifier_range_init(&range, src, vma->vm_start, + vma->vm_end); + mmu_notifier_invalidate_range_start(&range); + } else { + /* + * For shared mappings i_mmap_rwsem must be held to call + * huge_pte_alloc, otherwise the returned ptep could go + * away if part of a shared pmd and another thread calls + * huge_pmd_unshare. + */ + i_mmap_lock_read(mapping); + } for (addr = vma->vm_start; addr < vma->vm_end; addr += sz) { spinlock_t *src_ptl, *dst_ptl; + src_pte = huge_pte_offset(src, addr, sz); if (!src_pte) continue; + dst_pte = huge_pte_alloc(dst, addr, sz); if (!dst_pte) { ret = -ENOMEM; @@ -3325,7 +3336,9 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, } if (cow) - mmu_notifier_invalidate_range_end(src, mmun_start, mmun_end); + mmu_notifier_invalidate_range_end(&range); + else + i_mmap_unlock_read(mapping); return ret; } @@ -3342,8 +3355,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, struct page *page; struct hstate *h = hstate_vma(vma); unsigned long sz = huge_page_size(h); - unsigned long mmun_start = start; /* For mmu_notifiers */ - unsigned long mmun_end = end; /* For mmu_notifiers */ + struct mmu_notifier_range range; WARN_ON(!is_vm_hugetlb_page(vma)); BUG_ON(start & ~huge_page_mask(h)); @@ -3359,8 +3371,9 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, /* * If sharing possible, alert mmu notifiers of worst case. */ - adjust_range_if_pmd_sharing_possible(vma, &mmun_start, &mmun_end); - mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + mmu_notifier_range_init(&range, mm, start, end); + adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end); + mmu_notifier_invalidate_range_start(&range); address = start; for (; address < end; address += sz) { ptep = huge_pte_offset(mm, address, sz); @@ -3428,7 +3441,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, if (ref_page) break; } - mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + mmu_notifier_invalidate_range_end(&range); tlb_end_vma(tlb, vma); } @@ -3546,9 +3559,8 @@ static vm_fault_t hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma, struct page *old_page, *new_page; int outside_reserve = 0; vm_fault_t ret = 0; - unsigned long mmun_start; /* For mmu_notifiers */ - unsigned long mmun_end; /* For mmu_notifiers */ unsigned long haddr = address & huge_page_mask(h); + struct mmu_notifier_range range; pte = huge_ptep_get(ptep); old_page = pte_page(pte); @@ -3627,9 +3639,8 @@ retry_avoidcopy: __SetPageUptodate(new_page); set_page_huge_active(new_page); - mmun_start = haddr; - mmun_end = mmun_start + huge_page_size(h); - mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + mmu_notifier_range_init(&range, mm, haddr, haddr + huge_page_size(h)); + mmu_notifier_invalidate_range_start(&range); /* * Retake the page table lock to check for racing updates @@ -3642,7 +3653,7 @@ retry_avoidcopy: /* Break COW */ huge_ptep_clear_flush(vma, haddr, ptep); - mmu_notifier_invalidate_range(mm, mmun_start, mmun_end); + mmu_notifier_invalidate_range(mm, range.start, range.end); set_huge_pte_at(mm, haddr, ptep, make_huge_pte(vma, new_page, 1)); page_remove_rmap(old_page, true); @@ -3651,7 +3662,7 @@ retry_avoidcopy: new_page = old_page; } spin_unlock(ptl); - mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + mmu_notifier_invalidate_range_end(&range); out_release_all: restore_reserve_on_error(h, vma, haddr, new_page); put_page(new_page); @@ -3744,16 +3755,16 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, } /* - * Use page lock to guard against racing truncation - * before we get page_table_lock. + * We can not race with truncation due to holding i_mmap_rwsem. + * Check once here for faults beyond end of file. */ + size = i_size_read(mapping->host) >> huge_page_shift(h); + if (idx >= size) + goto out; + retry: page = find_lock_page(mapping, idx); if (!page) { - size = i_size_read(mapping->host) >> huge_page_shift(h); - if (idx >= size) - goto out; - /* * Check for page in userfault range */ @@ -3773,14 +3784,18 @@ retry: }; /* - * hugetlb_fault_mutex must be dropped before - * handling userfault. Reacquire after handling - * fault to make calling code simpler. + * hugetlb_fault_mutex and i_mmap_rwsem must be + * dropped before handling userfault. Reacquire + * after handling fault to make calling code simpler. */ hash = hugetlb_fault_mutex_hash(h, mm, vma, mapping, idx, haddr); mutex_unlock(&hugetlb_fault_mutex_table[hash]); + i_mmap_unlock_read(mapping); + ret = handle_userfault(&vmf, VM_UFFD_MISSING); + + i_mmap_lock_read(mapping); mutex_lock(&hugetlb_fault_mutex_table[hash]); goto out; } @@ -3839,9 +3854,6 @@ retry: } ptl = huge_pte_lock(h, mm, ptep); - size = i_size_read(mapping->host) >> huge_page_shift(h); - if (idx >= size) - goto backout; ret = 0; if (!huge_pte_none(huge_ptep_get(ptep))) @@ -3928,6 +3940,11 @@ 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, mm, ptep); @@ -3935,20 +3952,33 @@ 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, haddr, huge_page_size(h)); - if (!ptep) - return VM_FAULT_OOM; } + /* + * Acquire i_mmap_rwsem before calling huge_pte_alloc and hold + * until finished with ptep. This serves two purposes: + * 1) It prevents huge_pmd_unshare from being called elsewhere + * and making the ptep no longer valid. + * 2) It synchronizes us with file truncation. + * + * ptep could have already be assigned via huge_pte_offset. That + * is OK, as huge_pte_alloc will return the same value unless + * something changed. + */ mapping = vma->vm_file->f_mapping; - idx = vma_hugecache_offset(h, vma, haddr); + i_mmap_lock_read(mapping); + ptep = huge_pte_alloc(mm, haddr, huge_page_size(h)); + if (!ptep) { + i_mmap_unlock_read(mapping); + return VM_FAULT_OOM; + } /* * 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. */ + idx = vma_hugecache_offset(h, vma, haddr); hash = hugetlb_fault_mutex_hash(h, mm, vma, mapping, idx, haddr); mutex_lock(&hugetlb_fault_mutex_table[hash]); @@ -4036,6 +4066,7 @@ out_ptl: } out_mutex: mutex_unlock(&hugetlb_fault_mutex_table[hash]); + i_mmap_unlock_read(mapping); /* * Generally it's safe to hold refcount during waiting page lock. But * here we just wait to defer the next page fault to avoid busy loop and @@ -4340,21 +4371,21 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, pte_t pte; struct hstate *h = hstate_vma(vma); unsigned long pages = 0; - unsigned long f_start = start; - unsigned long f_end = end; bool shared_pmd = false; + struct mmu_notifier_range range; /* * In the case of shared PMDs, the area to flush could be beyond - * start/end. Set f_start/f_end to cover the maximum possible + * start/end. Set range.start/range.end to cover the maximum possible * range if PMD sharing is possible. */ - adjust_range_if_pmd_sharing_possible(vma, &f_start, &f_end); + mmu_notifier_range_init(&range, mm, start, end); + adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end); BUG_ON(address >= end); - flush_cache_range(vma, f_start, f_end); + flush_cache_range(vma, range.start, range.end); - mmu_notifier_invalidate_range_start(mm, f_start, f_end); + mmu_notifier_invalidate_range_start(&range); i_mmap_lock_write(vma->vm_file->f_mapping); for (; address < end; address += huge_page_size(h)) { spinlock_t *ptl; @@ -4405,7 +4436,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, * did unshare a page of pmds, flush the range corresponding to the pud. */ if (shared_pmd) - flush_hugetlb_tlb_range(vma, f_start, f_end); + flush_hugetlb_tlb_range(vma, range.start, range.end); else flush_hugetlb_tlb_range(vma, start, end); /* @@ -4415,7 +4446,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, * See Documentation/vm/mmu_notifier.rst */ i_mmap_unlock_write(vma->vm_file->f_mapping); - mmu_notifier_invalidate_range_end(mm, f_start, f_end); + mmu_notifier_invalidate_range_end(&range); return pages << h->order; } @@ -4640,10 +4671,12 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, * Search for a shareable pmd page for hugetlb. In any case calls pmd_alloc() * and returns the corresponding pte. While this is not necessary for the * !shared pmd case because we can allocate the pmd later as well, it makes the - * code much cleaner. pmd allocation is essential for the shared case because - * pud has to be populated inside the same i_mmap_rwsem section - otherwise - * racing tasks could either miss the sharing (see huge_pte_offset) or select a - * bad pmd for sharing. + * code much cleaner. + * + * This routine must be called with i_mmap_rwsem held in at least read mode. + * For hugetlbfs, this prevents removal of any page table entries associated + * with the address space. This is important as we are setting up sharing + * based on existing page table entries (mappings). */ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud) { @@ -4660,7 +4693,6 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud) if (!vma_shareable(vma, addr)) return (pte_t *)pmd_alloc(mm, pud, addr); - i_mmap_lock_write(mapping); vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) { if (svma == vma) continue; @@ -4690,7 +4722,6 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud) spin_unlock(ptl); out: pte = (pte_t *)pmd_alloc(mm, pud, addr); - i_mmap_unlock_write(mapping); return pte; } @@ -4701,7 +4732,7 @@ out: * indicated by page_count > 1, unmap is achieved by clearing pud and * decrementing the ref count. If count == 1, the pte page is not shared. * - * called with page table lock held. + * Called with page table lock held and i_mmap_rwsem held in write mode. * * returns: 1 successfully unmapped a shared pte page * 0 the underlying pte page is not shared, or it is the last user |
