mm/hmm: do not differentiate between empty entry or missing directory

There is no point in differentiating between a range for which there is
not even a directory (and thus entries) and empty entry (pte_none() or
pmd_none() returns true).

Simply drop the distinction ie remove HMM_PFN_EMPTY flag and merge now
duplicate hmm_vma_walk_hole() and hmm_vma_walk_clear() functions.

Link: http://lkml.kernel.org/r/20180323005527.758-11-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>

1 files changed, 15 insertions, 30 deletions

diff --git a/mm/hmm.c b/mm/hmm.c
index a93c1e35df91..b8affe0bf4eb 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -348,6 +348,16 @@ static void hmm_pfns_clear(uint64_t *pfns,
                 *pfns = 0;
 }
 
+/*
+ * hmm_vma_walk_hole() - handle a range lacking valid pmd or pte(s)
+ * @start: range virtual start address (inclusive)
+ * @end: range virtual end address (exclusive)
+ * @walk: mm_walk structure
+ * Returns: 0 on success, -EAGAIN after page fault, or page fault error
+ *
+ * This function will be called whenever pmd_none() or pte_none() returns true,
+ * or whenever there is no page directory covering the virtual address range.
+ */
 static int hmm_vma_walk_hole(unsigned long addr,
                              unsigned long end,
                              struct mm_walk *walk)
@@ -360,31 +370,6 @@ static int hmm_vma_walk_hole(unsigned long addr,
         hmm_vma_walk->last = addr;
         i = (addr - range->start) >> PAGE_SHIFT;
         for (; addr < end; addr += PAGE_SIZE, i++) {
-                pfns[i] = HMM_PFN_EMPTY;
-                if (hmm_vma_walk->fault) {
-                        int ret;
-
-                        ret = hmm_vma_do_fault(walk, addr, &pfns[i]);
-                        if (ret != -EAGAIN)
-                                return ret;
-                }
-        }
-
-        return hmm_vma_walk->fault ? -EAGAIN : 0;
-}
-
-static int hmm_vma_walk_clear(unsigned long addr,
-                              unsigned long end,
-                              struct mm_walk *walk)
-{
-        struct hmm_vma_walk *hmm_vma_walk = walk->private;
-        struct hmm_range *range = hmm_vma_walk->range;
-        uint64_t *pfns = range->pfns;
-        unsigned long i;
-
-        hmm_vma_walk->last = addr;
-        i = (addr - range->start) >> PAGE_SHIFT;
-        for (; addr < end; addr += PAGE_SIZE, i++) {
                 pfns[i] = 0;
                 if (hmm_vma_walk->fault) {
                         int ret;
@@ -440,10 +425,10 @@ again:
                 if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
                         goto again;
                 if (pmd_protnone(pmd))
-                        return hmm_vma_walk_clear(start, end, walk);
+                        return hmm_vma_walk_hole(start, end, walk);
 
                 if (write_fault && !pmd_write(pmd))
-                        return hmm_vma_walk_clear(start, end, walk);
+                        return hmm_vma_walk_hole(start, end, walk);
 
                 pfn = pmd_pfn(pmd) + pte_index(addr);
                 flag |= pmd_write(pmd) ? HMM_PFN_WRITE : 0;
@@ -462,7 +447,7 @@ again:
                 pfns[i] = 0;
 
                 if (pte_none(pte)) {
-                        pfns[i] = HMM_PFN_EMPTY;
+                        pfns[i] = 0;
                         if (hmm_vma_walk->fault)
                                 goto fault;
                         continue;
@@ -513,8 +498,8 @@ again:
 
 fault:
                 pte_unmap(ptep);
-                /* Fault all pages in range */
-                return hmm_vma_walk_clear(start, end, walk);
+                /* Fault any virtual address we were asked to fault */
+                return hmm_vma_walk_hole(start, end, walk);
         }
         pte_unmap(ptep - 1);