Commit 31383c68 authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds
Browse files

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@dwillia2-desk3.amr.corp.intel.com


Fixes: dee41079 ("/dev/dax, core: file operations and dax-mmap")
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 95a87982

include/linux/mm.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

mm/hugetlb.c

+8 −0
Original line number Diff line number Diff line
@@ -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,

mm/mmap.c

+5 −3
Original line number Diff line number Diff line
@@ -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)

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