mm/hmm: cleanup special vma handling (VM_SPECIAL)

Special vma (one with any of the VM_SPECIAL flags) can not be access by
device because there is no consistent model across device drivers on those
vma and their backing memory.

This patch directly use hmm_range struct for hmm_pfns_special() argument
as it is always affecting the whole vma and thus the whole range.

It also make behavior consistent after this patch both hmm_vma_fault() and
hmm_vma_get_pfns() returns -EINVAL when facing such vma.  Previously
hmm_vma_fault() returned 0 and hmm_vma_get_pfns() return -EINVAL but both
were filling the HMM pfn array with special entry.

Link: http://lkml.kernel.org/r/20180323005527.758-10-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/hmm.c b/mm/hmm.c
index b69f30fc064ba1639621259f30a55ff85673485b..a93c1e35df91d646cc139e46bef43ac1a645b736 100644 (file)
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -324,14 +324,6 @@ static int hmm_vma_do_fault(struct mm_walk *walk,
        return -EAGAIN;
 }
 
-static void hmm_pfns_special(uint64_t *pfns,
-                            unsigned long addr,
-                            unsigned long end)
-{
-       for (; addr < end; addr += PAGE_SIZE, pfns++)
-               *pfns = HMM_PFN_SPECIAL;
-}
-
 static int hmm_pfns_bad(unsigned long addr,
                        unsigned long end,
                        struct mm_walk *walk)
@@ -529,6 +521,14 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
        return 0;
 }
 
+static void hmm_pfns_special(struct hmm_range *range)
+{
+       unsigned long addr = range->start, i = 0;
+
+       for (; addr < range->end; addr += PAGE_SIZE, i++)
+               range->pfns[i] = HMM_PFN_SPECIAL;
+}
+
 /*
  * hmm_vma_get_pfns() - snapshot CPU page table for a range of virtual addresses
  * @range: range being snapshotted
@@ -553,12 +553,6 @@ int hmm_vma_get_pfns(struct hmm_range *range)
        struct mm_walk mm_walk;
        struct hmm *hmm;
 
-       /* FIXME support hugetlb fs */
-       if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
-               hmm_pfns_special(range->pfns, range->start, range->end);
-               return -EINVAL;
-       }
-
        /* Sanity check, this really should not happen ! */
        if (range->start < vma->vm_start || range->start >= vma->vm_end)
                return -EINVAL;
@@ -572,6 +566,12 @@ int hmm_vma_get_pfns(struct hmm_range *range)
        if (!hmm->mmu_notifier.ops)
                return -EINVAL;
 
+       /* FIXME support hugetlb fs */
+       if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
+               hmm_pfns_special(range);
+               return -EINVAL;
+       }
+
        if (!(vma->vm_flags & VM_READ)) {
                /*
                 * If vma do not allow read access, then assume that it does
@@ -740,6 +740,12 @@ int hmm_vma_fault(struct hmm_range *range, bool write, bool block)
        if (!hmm->mmu_notifier.ops)
                return -EINVAL;
 
+       /* FIXME support hugetlb fs */
+       if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
+               hmm_pfns_special(range);
+               return -EINVAL;
+       }
+
        if (!(vma->vm_flags & VM_READ)) {
                /*
                 * If vma do not allow read access, then assume that it does
@@ -751,12 +757,6 @@ int hmm_vma_fault(struct hmm_range *range, bool write, bool block)
                return -EPERM;
        }
 
-       /* FIXME support hugetlb fs */
-       if (is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_SPECIAL)) {
-               hmm_pfns_special(range->pfns, range->start, range->end);
-               return 0;
-       }
-
        /* Initialize range to track CPU page table update */
        spin_lock(&hmm->lock);
        range->valid = true;