The patch titled
Subject: userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings-update
has been added to the -mm tree. Its filename is
userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings-update.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings-update.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings-update.patch
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------------------------------------------------------
From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Subject: userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings-update
Thanks Andrea, I incorporated your suggestions into a new version of the patch.
While changing (dst_vma->vm_flags & VM_SHARED) to integers, I noticed an issue
in the error path of __mcopy_atomic_hugetlb().
> */
> - ClearPagePrivate(page);
> + if (dst_vma->vm_flags & VM_SHARED)
> + SetPagePrivate(page);
> + else
> + ClearPagePrivate(page);
> put_page(page);
We can not use dst_vma here as it may be different than the vma for which the
page was originally allocated, or even NULL. Remember, we may drop mmap_sem
and look up dst_vma again. Therefore, we need to save the value of
(dst_vma->vm_flags & VM_SHARED) for the vma which was used when the page was
allocated. This change as well as your suggestions are in the patch below:
Link: http://lkml.kernel.org/r/c9c8cafe-baa7-05b4-34ea-1dfa5523a85f@xxxxxxxxxx
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 9 +++++----
mm/userfaultfd.c | 22 ++++++++++++++++++----
2 files changed, 23 insertions(+), 8 deletions(-)
diff -puN mm/hugetlb.c~userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings-update mm/hugetlb.c
--- a/mm/hugetlb.c~userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings-update
+++ a/mm/hugetlb.c
@@ -3992,6 +3992,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
unsigned long src_addr,
struct page **pagep)
{
+ int vm_shared = dst_vma->vm_flags & VM_SHARED;
struct hstate *h = hstate_vma(dst_vma);
pte_t _dst_pte;
spinlock_t *ptl;
@@ -4031,7 +4032,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
/*
* If shared, add to page cache
*/
- if (dst_vma->vm_flags & VM_SHARED) {
+ if (vm_shared) {
struct address_space *mapping = dst_vma->vm_file->f_mapping;
pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr);
@@ -4047,7 +4048,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
if (!huge_pte_none(huge_ptep_get(dst_pte)))
goto out_release_unlock;
- if (dst_vma->vm_flags & VM_SHARED) {
+ if (vm_shared) {
page_dup_rmap(page, true);
} else {
ClearPagePrivate(page);
@@ -4069,7 +4070,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
update_mmu_cache(dst_vma, dst_addr, dst_pte);
spin_unlock(ptl);
- if (dst_vma->vm_flags & VM_SHARED)
+ if (vm_shared)
unlock_page(page);
ret = 0;
out:
@@ -4077,7 +4078,7 @@ out:
out_release_unlock:
spin_unlock(ptl);
out_release_nounlock:
- if (dst_vma->vm_flags & VM_SHARED)
+ if (vm_shared)
unlock_page(page);
put_page(page);
goto out;
diff -puN mm/userfaultfd.c~userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings-update mm/userfaultfd.c
--- a/mm/userfaultfd.c~userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings-update
+++ a/mm/userfaultfd.c
@@ -154,6 +154,8 @@ static __always_inline ssize_t __mcopy_a
unsigned long len,
bool zeropage)
{
+ int vm_alloc_shared = dst_vma->vm_flags & VM_SHARED;
+ int vm_shared = dst_vma->vm_flags & VM_SHARED;
ssize_t err;
pte_t *dst_pte;
unsigned long src_addr, dst_addr;
@@ -210,6 +212,8 @@ retry:
if (dst_start < dst_vma->vm_start ||
dst_start + len > dst_vma->vm_end)
goto out_unlock;
+
+ vm_shared = dst_vma->vm_flags & VM_SHARED;
}
if (WARN_ON(dst_addr & (vma_hpagesize - 1) ||
@@ -226,7 +230,7 @@ retry:
* If not shared, ensure the dst_vma has a anon_vma.
*/
err = -ENOMEM;
- if (!(dst_vma->vm_flags & VM_SHARED)) {
+ if (!vm_shared) {
if (unlikely(anon_vma_prepare(dst_vma)))
goto out_unlock;
}
@@ -266,6 +270,7 @@ retry:
dst_addr, src_addr, &page);
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
+ vm_alloc_shared = vm_shared;
cond_resched();
@@ -339,8 +344,12 @@ out:
* reserved page. In this case, set PagePrivate so that the
* global reserve count will be incremented to match the
* reservation map entry which was created.
+ *
+ * Note that vm_alloc_shared is based on the flags of the vma
+ * for which the page was originally allocated. dst_vma could
+ * be different or NULL on error.
*/
- if (dst_vma->vm_flags & VM_SHARED)
+ if (vm_alloc_shared)
SetPagePrivate(page);
else
ClearPagePrivate(page);
@@ -399,9 +408,14 @@ retry:
dst_vma = find_vma(dst_mm, dst_start);
if (!dst_vma)
goto out_unlock;
- if (!vma_is_shmem(dst_vma) && !is_vm_hugetlb_page(dst_vma) &&
- dst_vma->vm_flags & VM_SHARED)
+ /*
+ * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
+ * it will overwrite vm_ops, so vma_is_anonymous must return false.
+ */
+ if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
+ dst_vma->vm_flags & VM_SHARED))
goto out_unlock;
+
if (dst_start < dst_vma->vm_start ||
dst_start + len > dst_vma->vm_end)
goto out_unlock;
_
Patches currently in -mm which might be from mike.kravetz@xxxxxxxxxx are
userfaultfd-hugetlbfs-add-copy_huge_page_from_user-for-hugetlb-userfaultfd-support.patch
userfaultfd-hugetlbfs-add-hugetlb_mcopy_atomic_pte-for-userfaultfd-support.patch
userfaultfd-hugetlbfs-add-__mcopy_atomic_hugetlb-for-huge-page-uffdio_copy.patch
userfaultfd-hugetlbfs-fix-__mcopy_atomic_hugetlb-retry-error-processing.patch
userfaultfd-hugetlbfs-add-userfaultfd-hugetlb-hook.patch
userfaultfd-hugetlbfs-allow-registration-of-ranges-containing-huge-pages.patch
userfaultfd-hugetlbfs-add-userfaultfd_hugetlb-test.patch
userfaultfd-hugetlbfs-userfaultfd_huge_must_wait-for-hugepmd-ranges.patch
userfaultfd-hugetlbfs-reserve-count-on-error-in-__mcopy_atomic_hugetlb.patch
userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings.patch
userfaultfd-hugetlbfs-add-uffdio_copy-support-for-shared-mappings-update.patch
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