4.9-stable review patch. If anyone has any objections, please let me know.
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From: Dan Williams dan.j.williams@intel.com
commit 31383c6865a578834dd953d9dbc88e6b19fe3997 upstream.
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@dwillia... Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap") Signed-off-by: Dan Williams dan.j.williams@intel.com Cc: Jeff Moyer jmoyer@redhat.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/linux/mm.h | 1 + mm/hugetlb.c | 8 ++++++++ mm/mmap.c | 8 +++++--- 3 files changed, 14 insertions(+), 3 deletions(-)
--- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -347,6 +347,7 @@ struct fault_env { 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_area_struct *vma, struct vm_fault *vmf); int (*pmd_fault)(struct vm_area_struct *, unsigned long address, --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3135,6 +3135,13 @@ 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 @@ -3151,6 +3158,7 @@ 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, --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2538,9 +2538,11 @@ static int __split_vma(struct mm_struct 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)