Factor out one small part of the shmem pmd handling: the arch-specific
get_user_pages_fast() has special code to cope with the peculiar
refcounting on anonymous THP tail pages (and on hugetlbfs tail pages):
which must be avoided in the straightforward shmem pmd case.
Signed-off-by: Hugh Dickins <hu...@google.com>
---
arch/mips/mm/gup.c | 17 ++++++++++++-----
arch/s390/mm/gup.c | 22 +++++++++++++++++++++-
arch/sparc/mm/gup.c | 22 +++++++++++++++++++++-
arch/x86/mm/gup.c | 17 ++++++++++++-----
mm/gup.c | 22 +++++++++++++++++++++-
5 files changed, 87 insertions(+), 13 deletions(-)
--- thpfs.orig/arch/mips/mm/gup.c 2015-02-08 18:54:22.000000000 -0800
+++ thpfs/arch/mips/mm/gup.c 2015-02-20 19:34:26.971957306 -0800
@@ -64,7 +64,8 @@ static inline void get_head_page_multipl
{
VM_BUG_ON(page != compound_head(page));
VM_BUG_ON(page_count(page) == 0);
- atomic_add(nr, &page->_count);
+ if (nr)
+ atomic_add(nr, &page->_count);
SetPageReferenced(page);
}
@@ -85,13 +86,19 @@ static int gup_huge_pmd(pmd_t pmd, unsig
head = pte_page(pte);
page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
do {
- VM_BUG_ON(compound_head(page) != head);
- pages[*nr] = page;
- if (PageTail(page))
+ if (PageTail(page)) {
+ VM_BUG_ON(compound_head(page) != head);
get_huge_page_tail(page);
+ refs++;
+ } else {
+ /*
+ * Handle head or huge tmpfs with normal refcounting.
+ */
+ get_page(page);
+ }
+ pages[*nr] = page;
(*nr)++;
page++;
- refs++;
} while (addr += PAGE_SIZE, addr != end);
get_head_page_multiple(head, refs);
--- thpfs.orig/arch/s390/mm/gup.c 2014-01-19 18:40:07.000000000 -0800
+++ thpfs/arch/s390/mm/gup.c 2015-02-20 19:34:26.971957306 -0800
@@ -61,10 +61,30 @@ static inline int gup_huge_pmd(pmd_t *pm
return 0;
VM_BUG_ON(!pfn_valid(pmd_val(pmd) >> PAGE_SHIFT));
- refs = 0;
head = pmd_page(pmd);
page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+
+ if (!PageHead(head)) {
+ /*
+ * Handle a huge tmpfs team with normal refcounting.
+ */
+ do {
+ if (!page_cache_get_speculative(page))
+ return 0;
+ if (unlikely(pmd_val(pmd) != pmd_val(*pmdp))) {
+ put_page(page);
+ return 0;
+ }
+ pages[*nr] = page;
+ (*nr)++;
+ page++;
+ } while (addr += PAGE_SIZE, addr != end);
+ return 1;
+ }
+
tail = page;
+ refs = 0;
+
do {
VM_BUG_ON(compound_head(page) != head);
pages[*nr] = page;
--- thpfs.orig/arch/sparc/mm/gup.c 2014-12-07 14:21:05.000000000 -0800
+++ thpfs/arch/sparc/mm/gup.c 2015-02-20 19:34:26.975957297 -0800
@@ -79,10 +79,30 @@ static int gup_huge_pmd(pmd_t *pmdp, pmd
if (write && !pmd_write(pmd))
return 0;
- refs = 0;
head = pmd_page(pmd);
page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+
+ if (!PageHead(head)) {
+ /*
+ * Handle a huge tmpfs team with normal refcounting.
+ */
+ do {
+ if (!page_cache_get_speculative(page))
+ return 0;
+ if (unlikely(pmd_val(pmd) != pmd_val(*pmdp))) {
+ put_page(page);
+ return 0;
+ }
+ pages[*nr] = page;
+ (*nr)++;
+ page++;
+ } while (addr += PAGE_SIZE, addr != end);
+ return 1;
+ }
+
tail = page;
+ refs = 0;
+
do {
VM_BUG_ON(compound_head(page) != head);
pages[*nr] = page;
--- thpfs.orig/arch/x86/mm/gup.c 2015-02-08 18:54:22.000000000 -0800
+++ thpfs/arch/x86/mm/gup.c 2015-02-20 19:34:26.975957297 -0800
@@ -110,7 +110,8 @@ static inline void get_head_page_multipl
{
VM_BUG_ON_PAGE(page != compound_head(page), page);
VM_BUG_ON_PAGE(page_count(page) == 0, page);
- atomic_add(nr, &page->_count);
+ if (nr)
+ atomic_add(nr, &page->_count);
SetPageReferenced(page);
}
@@ -135,13 +136,19 @@ static noinline int gup_huge_pmd(pmd_t p
head = pte_page(pte);
page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
do {
- VM_BUG_ON_PAGE(compound_head(page) != head, page);
- pages[*nr] = page;
- if (PageTail(page))
+ if (PageTail(page)) {
+ VM_BUG_ON_PAGE(compound_head(page) != head, page);
get_huge_page_tail(page);
+ refs++;
+ } else {
+ /*
+ * Handle head or huge tmpfs with normal refcounting.
+ */
+ get_page(page);
+ }
+ pages[*nr] = page;
(*nr)++;
page++;
- refs++;
} while (addr += PAGE_SIZE, addr != end);
get_head_page_multiple(head, refs);
--- thpfs.orig/mm/gup.c 2015-02-08 18:54:22.000000000 -0800
+++ thpfs/mm/gup.c 2015-02-20 19:34:26.975957297 -0800
@@ -795,10 +795,30 @@ static int gup_huge_pmd(pmd_t orig, pmd_
if (write && !pmd_write(orig))
return 0;
- refs = 0;
head = pmd_page(orig);
page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+
+ if (!PageHead(head)) {
+ /*
+ * Handle a huge tmpfs team with normal refcounting.
+ */
+ do {
+ if (!page_cache_get_speculative(page))
+ return 0;
+ if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
+ put_page(page);
+ return 0;
+ }
+ pages[*nr] = page;
+ (*nr)++;
+ page++;
+ } while (addr += PAGE_SIZE, addr != end);
+ return 1;
+ }
+
tail = page;
+ refs = 0;
+
do {
VM_BUG_ON_PAGE(compound_head(page) != head, page);
pages[*nr] = page;
--
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