diff options
| -rw-r--r-- | include/linux/hugetlb.h | 3 | ||||
| -rw-r--r-- | mm/hugetlb.c | 60 | ||||
| -rw-r--r-- | mm/vma.c | 7 | ||||
| -rw-r--r-- | tools/testing/vma/vma_internal.h | 2 |
4 files changed, 56 insertions, 16 deletions
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 0598f36931de..42f374e828a2 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -279,6 +279,7 @@ bool is_hugetlb_entry_migration(pte_t pte); bool is_hugetlb_entry_hwpoisoned(pte_t pte); void hugetlb_unshare_all_pmds(struct vm_area_struct *vma); void fixup_hugetlb_reservations(struct vm_area_struct *vma); +void hugetlb_split(struct vm_area_struct *vma, unsigned long addr); #else /* !CONFIG_HUGETLB_PAGE */ @@ -476,6 +477,8 @@ static inline void fixup_hugetlb_reservations(struct vm_area_struct *vma) { } +static inline void hugetlb_split(struct vm_area_struct *vma, unsigned long addr) {} + #endif /* !CONFIG_HUGETLB_PAGE */ #ifndef pgd_write diff --git a/mm/hugetlb.c b/mm/hugetlb.c index f0b1d53079f9..7ba020d489d4 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -121,7 +121,7 @@ static void hugetlb_vma_lock_free(struct vm_area_struct *vma); static void hugetlb_vma_lock_alloc(struct vm_area_struct *vma); static void __hugetlb_vma_unlock_write_free(struct vm_area_struct *vma); static void hugetlb_unshare_pmds(struct vm_area_struct *vma, - unsigned long start, unsigned long end); + unsigned long start, unsigned long end, bool take_locks); static struct resv_map *vma_resv_map(struct vm_area_struct *vma); static void hugetlb_free_folio(struct folio *folio) @@ -5426,26 +5426,40 @@ static int hugetlb_vm_op_split(struct vm_area_struct *vma, unsigned long addr) { if (addr & ~(huge_page_mask(hstate_vma(vma)))) return -EINVAL; + return 0; +} +void hugetlb_split(struct vm_area_struct *vma, unsigned long addr) +{ /* * PMD sharing is only possible for PUD_SIZE-aligned address ranges * in HugeTLB VMAs. If we will lose PUD_SIZE alignment due to this * split, unshare PMDs in the PUD_SIZE interval surrounding addr now. + * This function is called in the middle of a VMA split operation, with + * MM, VMA and rmap all write-locked to prevent concurrent page table + * walks (except hardware and gup_fast()). */ + vma_assert_write_locked(vma); + i_mmap_assert_write_locked(vma->vm_file->f_mapping); + if (addr & ~PUD_MASK) { - /* - * hugetlb_vm_op_split is called right before we attempt to - * split the VMA. We will need to unshare PMDs in the old and - * new VMAs, so let's unshare before we split. - */ unsigned long floor = addr & PUD_MASK; unsigned long ceil = floor + PUD_SIZE; - if (floor >= vma->vm_start && ceil <= vma->vm_end) - hugetlb_unshare_pmds(vma, floor, ceil); + if (floor >= vma->vm_start && ceil <= vma->vm_end) { + /* + * Locking: + * Use take_locks=false here. + * The file rmap lock is already held. + * The hugetlb VMA lock can't be taken when we already + * hold the file rmap lock, and we don't need it because + * its purpose is to synchronize against concurrent page + * table walks, which are not possible thanks to the + * locks held by our caller. + */ + hugetlb_unshare_pmds(vma, floor, ceil, /* take_locks = */ false); + } } - - return 0; } static unsigned long hugetlb_vm_op_pagesize(struct vm_area_struct *vma) @@ -7885,9 +7899,16 @@ void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int re spin_unlock_irq(&hugetlb_lock); } +/* + * If @take_locks is false, the caller must ensure that no concurrent page table + * access can happen (except for gup_fast() and hardware page walks). + * If @take_locks is true, we take the hugetlb VMA lock (to lock out things like + * concurrent page fault handling) and the file rmap lock. + */ static void hugetlb_unshare_pmds(struct vm_area_struct *vma, unsigned long start, - unsigned long end) + unsigned long end, + bool take_locks) { struct hstate *h = hstate_vma(vma); unsigned long sz = huge_page_size(h); @@ -7911,8 +7932,12 @@ static void hugetlb_unshare_pmds(struct vm_area_struct *vma, mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, start, end); mmu_notifier_invalidate_range_start(&range); - hugetlb_vma_lock_write(vma); - i_mmap_lock_write(vma->vm_file->f_mapping); + if (take_locks) { + hugetlb_vma_lock_write(vma); + i_mmap_lock_write(vma->vm_file->f_mapping); + } else { + i_mmap_assert_write_locked(vma->vm_file->f_mapping); + } for (address = start; address < end; address += PUD_SIZE) { ptep = hugetlb_walk(vma, address, sz); if (!ptep) @@ -7922,8 +7947,10 @@ static void hugetlb_unshare_pmds(struct vm_area_struct *vma, spin_unlock(ptl); } flush_hugetlb_tlb_range(vma, start, end); - i_mmap_unlock_write(vma->vm_file->f_mapping); - hugetlb_vma_unlock_write(vma); + if (take_locks) { + i_mmap_unlock_write(vma->vm_file->f_mapping); + hugetlb_vma_unlock_write(vma); + } /* * No need to call mmu_notifier_arch_invalidate_secondary_tlbs(), see * Documentation/mm/mmu_notifier.rst. @@ -7938,7 +7965,8 @@ static void hugetlb_unshare_pmds(struct vm_area_struct *vma, void hugetlb_unshare_all_pmds(struct vm_area_struct *vma) { hugetlb_unshare_pmds(vma, ALIGN(vma->vm_start, PUD_SIZE), - ALIGN_DOWN(vma->vm_end, PUD_SIZE)); + ALIGN_DOWN(vma->vm_end, PUD_SIZE), + /* take_locks = */ true); } /* @@ -539,7 +539,14 @@ __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma, init_vma_prep(&vp, vma); vp.insert = new; vma_prepare(&vp); + + /* + * Get rid of huge pages and shared page tables straddling the split + * boundary. + */ vma_adjust_trans_huge(vma, vma->vm_start, addr, NULL); + if (is_vm_hugetlb_page(vma)) + hugetlb_split(vma, addr); if (new_below) { vma->vm_start = addr; diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h index 441feb21aa5a..4505b1c31be1 100644 --- a/tools/testing/vma/vma_internal.h +++ b/tools/testing/vma/vma_internal.h @@ -932,6 +932,8 @@ static inline void vma_adjust_trans_huge(struct vm_area_struct *vma, (void)next; } +static inline void hugetlb_split(struct vm_area_struct *, unsigned long) {} + static inline void vma_iter_free(struct vma_iterator *vmi) { mas_destroy(&vmi->mas); |