From: Dan Williams <dan.j.williams@xxxxxxxxx> Subject: mm, hugetlbfs: introduce ->split() to vm_operations_struct Patch series "device-dax: fix unaligned munmap handling" When device-dax is operating in huge-page mode we want it to behave like hugetlbfs and fail attempts to split vmas into unaligned ranges. It would be messy to teach the munmap path about device-dax alignment constraints in the same (hstate) way that hugetlbfs communicates this constraint. Instead, these patches introduce a new ->split() vm operation. This patch (of 2): The device-dax interface has similar constraints as hugetlbfs in that it requires the munmap path to unmap in huge page aligned units. Rather than add more custom vma handling code in __split_vma() introduce a new vm operation to perform this vma specific check. Link: http://lkml.kernel.org/r/151130418135.4029.6783191281930729710.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap") Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Jeff Moyer <jmoyer@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mm.h | 1 + mm/hugetlb.c | 8 ++++++++ mm/mmap.c | 8 +++++--- 3 files changed, 14 insertions(+), 3 deletions(-) diff -puN include/linux/mm.h~mm-hugetlbfs-introduce-split-to-vm_operations_struct include/linux/mm.h --- a/include/linux/mm.h~mm-hugetlbfs-introduce-split-to-vm_operations_struct +++ a/include/linux/mm.h @@ -377,6 +377,7 @@ enum page_entry_size { struct vm_operations_struct { void (*open)(struct vm_area_struct * area); void (*close)(struct vm_area_struct * area); + int (*split)(struct vm_area_struct * area, unsigned long addr); int (*mremap)(struct vm_area_struct * area); int (*fault)(struct vm_fault *vmf); int (*huge_fault)(struct vm_fault *vmf, enum page_entry_size pe_size); diff -puN mm/hugetlb.c~mm-hugetlbfs-introduce-split-to-vm_operations_struct mm/hugetlb.c --- a/mm/hugetlb.c~mm-hugetlbfs-introduce-split-to-vm_operations_struct +++ a/mm/hugetlb.c @@ -3125,6 +3125,13 @@ static void hugetlb_vm_op_close(struct v } } +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; +} + /* * We cannot handle pagefaults against hugetlb pages at all. They cause * handle_mm_fault() to try to instantiate regular-sized pages in the @@ -3141,6 +3148,7 @@ const struct vm_operations_struct hugetl .fault = hugetlb_vm_op_fault, .open = hugetlb_vm_op_open, .close = hugetlb_vm_op_close, + .split = hugetlb_vm_op_split, }; static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page, diff -puN mm/mmap.c~mm-hugetlbfs-introduce-split-to-vm_operations_struct mm/mmap.c --- a/mm/mmap.c~mm-hugetlbfs-introduce-split-to-vm_operations_struct +++ a/mm/mmap.c @@ -2555,9 +2555,11 @@ int __split_vma(struct mm_struct *mm, st struct vm_area_struct *new; int err; - if (is_vm_hugetlb_page(vma) && (addr & - ~(huge_page_mask(hstate_vma(vma))))) - return -EINVAL; + if (vma->vm_ops && vma->vm_ops->split) { + err = vma->vm_ops->split(vma, addr); + if (err) + return err; + } new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); if (!new) _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
