The patch titled
Subject: mm, hugetlbfs: introduce ->split() to vm_operations_struct
has been added to the -mm tree. Its filename is
mm-hugetlbfs-introduce-split-to-vm_operations_struct.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlbfs-introduce-split-to-vm_operations_struct.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlbfs-introduce-split-to-vm_operations_struct.patch
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------------------------------------------------------
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)
_
Patches currently in -mm which might be from dan.j.williams@xxxxxxxxx are
mm-fix-device-dax-pud-write-faults-triggered-by-get_user_pages.patch
mm-fix-device-dax-pud-write-faults-triggered-by-get_user_pages-v3.patch
mm-switch-to-define-pmd_write-instead-of-__have_arch_pmd_write.patch
mm-replace-pud_write-with-pud_access_permitted-in-fault-gup-paths.patch
mm-replace-pud_write-with-pud_access_permitted-in-fault-gup-paths-v3.patch
mm-replace-pmd_write-with-pmd_access_permitted-in-fault-gup-paths.patch
mm-replace-pte_write-with-pte_access_permitted-in-fault-gup-paths.patch
mm-hugetlbfs-introduce-split-to-vm_operations_struct.patch
device-dax-implement-split-to-catch-invalid-munmap-attempts.patch