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Date: Sun, 12 May 2013 04:23:34 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Andrea Arcangeli <aarcange@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Al Viro <viro@...iv.linux.org.uk>, Hugh Dickins <hughd@...gle.com>,
Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
Andi Kleen <ak@...ux.intel.com>,
Matthew Wilcox <matthew.r.wilcox@...el.com>,
"Kirill A. Shutemov" <kirill@...temov.name>,
Hillf Danton <dhillf@...il.com>, Dave Hansen <dave@...1.net>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv4 37/39] thp: handle write-protect exception to file-backed huge pages
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
VM_WRITE|VM_SHARED has already almost covered by do_wp_page_shared().
We only need to hadle locking differentely and setup pmd instead of pte.
do_huge_pmd_wp_page() itself needs only few minor changes:
- now we may need to allocate anon_vma on WP. Having huge page to COW
doesn't mean we have anon_vma, since the huge page can be file-backed.
- we need to adjust mm counters on COW file pages.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
include/linux/mm.h | 4 +++
mm/huge_memory.c | 17 +++++++++++--
mm/memory.c | 70 +++++++++++++++++++++++++++++++++++++++++-----------
3 files changed, 74 insertions(+), 17 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 563c8b7..7f3bc24 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1001,6 +1001,10 @@ extern int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, unsigned int flags);
extern int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
unsigned long address, unsigned int fault_flags);
+extern int do_wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmd, struct page *page,
+ pte_t *page_table, spinlock_t *ptl,
+ pte_t orig_pte, pmd_t orig_pmd);
#else
static inline int handle_mm_fault(struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long address,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 893cc69..d7c9df5 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1110,7 +1110,6 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
- VM_BUG_ON(!vma->anon_vma);
haddr = address & HPAGE_PMD_MASK;
if (is_huge_zero_pmd(orig_pmd))
goto alloc;
@@ -1120,7 +1119,7 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
page = pmd_page(orig_pmd);
VM_BUG_ON(!PageCompound(page) || !PageHead(page));
- if (page_mapcount(page) == 1) {
+ if (PageAnon(page) && page_mapcount(page) == 1) {
pmd_t entry;
entry = pmd_mkyoung(orig_pmd);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
@@ -1129,9 +1128,18 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
ret |= VM_FAULT_WRITE;
goto out_unlock;
}
+
+ if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) == (VM_WRITE|VM_SHARED)) {
+ pte_t __unused;
+ return do_wp_page_shared(mm, vma, address, pmd, page,
+ NULL, NULL, __unused, orig_pmd);
+ }
get_page(page);
spin_unlock(&mm->page_table_lock);
alloc:
+ if (unlikely(anon_vma_prepare(vma)))
+ return VM_FAULT_OOM;
+
if (transparent_hugepage_enabled(vma) &&
!transparent_hugepage_debug_cow())
new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
@@ -1195,6 +1203,11 @@ alloc:
add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
put_huge_zero_page();
} else {
+ if (!PageAnon(page)) {
+ /* File page COWed with anon page */
+ add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
+ add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
+ }
VM_BUG_ON(!PageHead(page));
page_remove_rmap(page);
put_page(page);
diff --git a/mm/memory.c b/mm/memory.c
index 4685dd1..ebff552 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2640,16 +2640,33 @@ static void mkwrite_pte(struct vm_area_struct *vma, unsigned long address,
update_mmu_cache(vma, address, page_table);
}
+static void mkwrite_pmd(struct vm_area_struct *vma, unsigned long address,
+ pmd_t *pmd, pmd_t orig_pmd)
+{
+ pmd_t entry;
+ unsigned long haddr = address & HPAGE_PMD_MASK;
+
+ flush_cache_page(vma, address, pmd_pfn(orig_pmd));
+ entry = pmd_mkyoung(orig_pmd);
+ entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+ if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
+ update_mmu_cache_pmd(vma, address, pmd);
+}
+
/*
* Only catch write-faults on shared writable pages, read-only shared pages can
* get COWed by get_user_pages(.write=1, .force=1).
*/
-static int do_wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long address, pte_t *page_table, pmd_t *pmd,
- spinlock_t *ptl, pte_t orig_pte, struct page *page)
+int do_wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmd, struct page *page,
+ pte_t *page_table, spinlock_t *ptl,
+ pte_t orig_pte, pmd_t orig_pmd)
{
struct vm_fault vmf;
bool page_mkwrite = false;
+ /* no page_table means caller asks for THP */
+ bool thp = (page_table == NULL) &&
+ IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE);
int tmp, ret = 0;
if (vma->vm_ops && vma->vm_ops->page_mkwrite)
@@ -2660,6 +2677,9 @@ static int do_wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,
vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
vmf.page = page;
+ if (thp)
+ vmf.flags |= FAULT_FLAG_TRANSHUGE;
+
/*
* Notify the address space that the page is about to
* become writable so that it can prohibit this or wait
@@ -2669,7 +2689,10 @@ static int do_wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,
* sleep if it needs to.
*/
page_cache_get(page);
- pte_unmap_unlock(page_table, ptl);
+ if (thp)
+ spin_unlock(&mm->page_table_lock);
+ else
+ pte_unmap_unlock(page_table, ptl);
tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
@@ -2693,19 +2716,34 @@ static int do_wp_page_shared(struct mm_struct *mm, struct vm_area_struct *vma,
* they did, we just return, as we can count on the
* MMU to tell us if they didn't also make it writable.
*/
- page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
- if (!pte_same(*page_table, orig_pte)) {
- unlock_page(page);
- pte_unmap_unlock(page_table, ptl);
- page_cache_release(page);
- return ret;
+ if (thp) {
+ spin_lock(&mm->page_table_lock);
+ if (unlikely(!pmd_same(*pmd, orig_pmd))) {
+ unlock_page(page);
+ spin_unlock(&mm->page_table_lock);
+ page_cache_release(page);
+ return ret;
+ }
+ } else {
+ page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+ if (!pte_same(*page_table, orig_pte)) {
+ unlock_page(page);
+ pte_unmap_unlock(page_table, ptl);
+ page_cache_release(page);
+ return ret;
+ }
}
page_mkwrite = true;
mkwrite_done:
get_page(page);
- mkwrite_pte(vma, address, page_table, orig_pte);
- pte_unmap_unlock(page_table, ptl);
+ if (thp) {
+ mkwrite_pmd(vma, address, pmd, orig_pmd);
+ spin_unlock(&mm->page_table_lock);
+ } else {
+ mkwrite_pte(vma, address, page_table, orig_pte);
+ pte_unmap_unlock(page_table, ptl);
+ }
dirty_page(vma, page, page_mkwrite);
return ret | VM_FAULT_WRITE;
}
@@ -2787,9 +2825,11 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
}
unlock_page(old_page);
} else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
- (VM_WRITE|VM_SHARED)))
- return do_wp_page_shared(mm, vma, address, page_table, pmd, ptl,
- orig_pte, old_page);
+ (VM_WRITE|VM_SHARED))) {
+ pmd_t __unused;
+ return do_wp_page_shared(mm, vma, address, pmd, old_page,
+ page_table, ptl, orig_pte, __unused);
+ }
/*
* Ok, we need to copy. Oh, well..
--
1.7.10.4
--
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