mm/gup: Implement the dev_pagemap() logic in the generic get_user_pages_fast() function

This is a preparation patch for the transition of x86 to the generic GUP_fast()
implementation.

Prepare generic GUP_fast() to handle dev_pagemap(). At the moment, it's
only implemented on x86. On non-x86, the new code will be compiled out.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aneesh Kumar K . V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dann Frazier <dann.frazier@canonical.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170316152655.37789-6-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5f01c88f0800daaacca6f9b2a272e657552af4c9..e197d3ca3e8a4119dc2c70ddaf8151b19aabe12a 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -430,6 +430,10 @@ static inline int pud_devmap(pud_t pud)
 {
        return 0;
 }
+static inline int pgd_devmap(pgd_t pgd)
+{
+       return 0;
+}
 #endif
 
 /*

diff --git a/mm/gup.c b/mm/gup.c
index 2b6cd35734570dd09f98cdb8d263187b33f5f15c..e3d1e80424f495a944132aaf635e412b5a35db10 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1200,12 +1200,23 @@ static inline pte_t gup_get_pte(pte_t *ptep)
 }
 #endif
 
+static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
+{
+       while ((*nr) - nr_start) {
+               struct page *page = pages[--(*nr)];
+
+               ClearPageReferenced(page);
+               put_page(page);
+       }
+}
+
 #ifdef __HAVE_ARCH_PTE_SPECIAL
 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
                         int write, struct page **pages, int *nr)
 {
+       struct dev_pagemap *pgmap = NULL;
+       int nr_start = *nr, ret = 0;
        pte_t *ptep, *ptem;
-       int ret = 0;
 
        ptem = ptep = pte_offset_map(&pmd, addr);
        do {
@@ -1222,7 +1233,13 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
                if (!pte_access_permitted(pte, write))
                        goto pte_unmap;
 
-               if (pte_special(pte))
+               if (pte_devmap(pte)) {
+                       pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
+                       if (unlikely(!pgmap)) {
+                               undo_dev_pagemap(nr, nr_start, pages);
+                               goto pte_unmap;
+                       }
+               } else if (pte_special(pte))
                        goto pte_unmap;
 
                VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
@@ -1239,6 +1256,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 
                VM_BUG_ON_PAGE(compound_head(page) != head, page);
 
+               put_dev_pagemap(pgmap);
                SetPageReferenced(page);
                pages[*nr] = page;
                (*nr)++;
@@ -1269,6 +1287,64 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 }
 #endif /* __HAVE_ARCH_PTE_SPECIAL */
 
+#ifdef __HAVE_ARCH_PTE_DEVMAP
+static int __gup_device_huge(unsigned long pfn, unsigned long addr,
+               unsigned long end, struct page **pages, int *nr)
+{
+       int nr_start = *nr;
+       struct dev_pagemap *pgmap = NULL;
+
+       do {
+               struct page *page = pfn_to_page(pfn);
+
+               pgmap = get_dev_pagemap(pfn, pgmap);
+               if (unlikely(!pgmap)) {
+                       undo_dev_pagemap(nr, nr_start, pages);
+                       return 0;
+               }
+               SetPageReferenced(page);
+               pages[*nr] = page;
+               get_page(page);
+               put_dev_pagemap(pgmap);
+               (*nr)++;
+               pfn++;
+       } while (addr += PAGE_SIZE, addr != end);
+       return 1;
+}
+
+static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
+               unsigned long end, struct page **pages, int *nr)
+{
+       unsigned long fault_pfn;
+
+       fault_pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+       return __gup_device_huge(fault_pfn, addr, end, pages, nr);
+}
+
+static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
+               unsigned long end, struct page **pages, int *nr)
+{
+       unsigned long fault_pfn;
+
+       fault_pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
+       return __gup_device_huge(fault_pfn, addr, end, pages, nr);
+}
+#else
+static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
+               unsigned long end, struct page **pages, int *nr)
+{
+       BUILD_BUG();
+       return 0;
+}
+
+static int __gup_device_huge_pud(pud_t pud, unsigned long addr,
+               unsigned long end, struct page **pages, int *nr)
+{
+       BUILD_BUG();
+       return 0;
+}
+#endif
+
 static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
                unsigned long end, int write, struct page **pages, int *nr)
 {
@@ -1278,6 +1354,9 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
        if (!pmd_access_permitted(orig, write))
                return 0;
 
+       if (pmd_devmap(orig))
+               return __gup_device_huge_pmd(orig, addr, end, pages, nr);
+
        refs = 0;
        head = pmd_page(orig);
        page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
@@ -1314,6 +1393,9 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
        if (!pud_access_permitted(orig, write))
                return 0;
 
+       if (pud_devmap(orig))
+               return __gup_device_huge_pud(orig, addr, end, pages, nr);
+
        refs = 0;
        head = pud_page(orig);
        page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
@@ -1351,6 +1433,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
        if (!pgd_access_permitted(orig, write))
                return 0;
 
+       BUILD_BUG_ON(pgd_devmap(orig));
        refs = 0;
        head = pgd_page(orig);
        page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);