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mm, hugetlbfs: introduce ->split() to vm_operations_struct

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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@dwillia2-desk3.amr.corp.intel.com
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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dan Williams 2017-11-29 16:10:28 -08:00 committed by Linus Torvalds
parent 95a8798254
commit 31383c6865
3 changed files with 14 additions and 3 deletions
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1
include/linux/mm.h
View File

@ -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);

8
mm/hugetlb.c
View File

@ -3125,6 +3125,13 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma)
}
}
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 hugetlb_vm_ops = {
.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,

8
mm/mmap.c
View File

@ -2555,9 +2555,11 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
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)