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Diffstat (limited to 'mm')
-rw-r--r--mm/gup.c95
1 files changed, 40 insertions, 55 deletions
diff --git a/mm/gup.c b/mm/gup.c
index 6cb71800fb5c..706f85b84f47 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1978,6 +1978,29 @@ static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
}
#endif
+static int record_subpages(struct page *page, unsigned long addr,
+ unsigned long end, struct page **pages)
+{
+ int nr;
+
+ for (nr = 0; addr != end; addr += PAGE_SIZE)
+ pages[nr++] = page++;
+
+ return nr;
+}
+
+static void put_compound_head(struct page *page, int refs)
+{
+ VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
+ /*
+ * Calling put_page() for each ref is unnecessarily slow. Only the last
+ * ref needs a put_page().
+ */
+ if (refs > 1)
+ page_ref_sub(page, refs - 1);
+ put_page(page);
+}
+
#ifdef CONFIG_ARCH_HAS_HUGEPD
static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
unsigned long sz)
@@ -2007,32 +2030,20 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
/* hugepages are never "special" */
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
- refs = 0;
head = pte_page(pte);
-
page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
- do {
- VM_BUG_ON(compound_head(page) != head);
- pages[*nr] = page;
- (*nr)++;
- page++;
- refs++;
- } while (addr += PAGE_SIZE, addr != end);
+ refs = record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(head, refs);
- if (!head) {
- *nr -= refs;
+ if (!head)
return 0;
- }
if (unlikely(pte_val(pte) != pte_val(*ptep))) {
- /* Could be optimized better */
- *nr -= refs;
- while (refs--)
- put_page(head);
+ put_compound_head(head, refs);
return 0;
}
+ *nr += refs;
SetPageReferenced(head);
return 1;
}
@@ -2079,28 +2090,19 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr);
}
- refs = 0;
page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
- do {
- pages[*nr] = page;
- (*nr)++;
- page++;
- refs++;
- } while (addr += PAGE_SIZE, addr != end);
+ refs = record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(pmd_page(orig), refs);
- if (!head) {
- *nr -= refs;
+ if (!head)
return 0;
- }
if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
- *nr -= refs;
- while (refs--)
- put_page(head);
+ put_compound_head(head, refs);
return 0;
}
+ *nr += refs;
SetPageReferenced(head);
return 1;
}
@@ -2120,28 +2122,19 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr);
}
- refs = 0;
page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
- do {
- pages[*nr] = page;
- (*nr)++;
- page++;
- refs++;
- } while (addr += PAGE_SIZE, addr != end);
+ refs = record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(pud_page(orig), refs);
- if (!head) {
- *nr -= refs;
+ if (!head)
return 0;
- }
if (unlikely(pud_val(orig) != pud_val(*pudp))) {
- *nr -= refs;
- while (refs--)
- put_page(head);
+ put_compound_head(head, refs);
return 0;
}
+ *nr += refs;
SetPageReferenced(head);
return 1;
}
@@ -2157,28 +2150,20 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
return 0;
BUILD_BUG_ON(pgd_devmap(orig));
- refs = 0;
+
page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
- do {
- pages[*nr] = page;
- (*nr)++;
- page++;
- refs++;
- } while (addr += PAGE_SIZE, addr != end);
+ refs = record_subpages(page, addr, end, pages + *nr);
head = try_get_compound_head(pgd_page(orig), refs);
- if (!head) {
- *nr -= refs;
+ if (!head)
return 0;
- }
if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
- *nr -= refs;
- while (refs--)
- put_page(head);
+ put_compound_head(head, refs);
return 0;
}
+ *nr += refs;
SetPageReferenced(head);
return 1;
}