diff --git a/mm/memory.c b/mm/memory.c
index a40e4b1cee4ff13cdca07b10a6afffa6933fcf30..24ba688876d636275811ab8a139e9eb6298059a5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1218,6 +1218,30 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
}
EXPORT_SYMBOL(remap_pfn_range);
+/*
+ * handle_pte_fault chooses page fault handler according to an entry
+ * which was read non-atomically. Before making any commitment, on
+ * those architectures or configurations (e.g. i386 with PAE) which
+ * might give a mix of unmatched parts, do_swap_page and do_file_page
+ * must check under lock before unmapping the pte and proceeding
+ * (but do_wp_page is only called after already making such a check;
+ * and do_anonymous_page and do_no_page can safely check later on).
+ */
+static inline int pte_unmap_same(struct mm_struct *mm,
+ pte_t *page_table, pte_t orig_pte)
+{
+ int same = 1;
+#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
+ if (sizeof(pte_t) > sizeof(unsigned long)) {
+ spin_lock(&mm->page_table_lock);
+ same = pte_same(*page_table, orig_pte);
+ spin_unlock(&mm->page_table_lock);
+ }
+#endif
+ pte_unmap(page_table);
+ return same;
+}
+
/*
* Do pte_mkwrite, but only if the vma says VM_WRITE. We do this when
* servicing faults for write access. In the normal case, do always want
@@ -1245,12 +1269,13 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
* change only once the write actually happens. This avoids a few races,
* and potentially makes it more efficient.
*
- * We hold the mm semaphore and the page_table_lock on entry and exit
- * with the page_table_lock released.
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), with pte both mapped and locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
*/
static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *page_table, pmd_t *pmd,
- pte_t orig_pte)
+ spinlock_t *ptl, pte_t orig_pte)
{
struct page *old_page, *new_page;
unsigned long pfn = pte_pfn(orig_pte);
@@ -1288,8 +1313,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
* Ok, we need to copy. Oh, well..
*/
page_cache_get(old_page);
- pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
+ pte_unmap_unlock(page_table, ptl);
if (unlikely(anon_vma_prepare(vma)))
goto oom;
@@ -1307,8 +1331,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
/*
* Re-check the pte - we dropped the lock
*/
- spin_lock(&mm->page_table_lock);
- page_table = pte_offset_map(pmd, address);
+ page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
if (likely(pte_same(*page_table, orig_pte))) {
page_remove_rmap(old_page);
if (!PageAnon(old_page)) {
@@ -1321,7 +1344,6 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
ptep_establish(vma, address, page_table, entry);
update_mmu_cache(vma, address, entry);
lazy_mmu_prot_update(entry);
-
lru_cache_add_active(new_page);
page_add_anon_rmap(new_page, vma, address);
@@ -1332,8 +1354,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
page_cache_release(new_page);
page_cache_release(old_page);
unlock:
- pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
+ pte_unmap_unlock(page_table, ptl);
return ret;
oom:
page_cache_release(old_page);
@@ -1660,20 +1681,22 @@ void swapin_readahead(swp_entry_t entry, unsigned long addr,struct vm_area_struc
}
/*
- * We hold the mm semaphore and the page_table_lock on entry and
- * should release the pagetable lock on exit..
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
*/
static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *page_table, pmd_t *pmd,
int write_access, pte_t orig_pte)
{
+ spinlock_t *ptl;
struct page *page;
swp_entry_t entry;
pte_t pte;
int ret = VM_FAULT_MINOR;
- pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
+ if (!pte_unmap_same(mm, page_table, orig_pte))
+ goto out;
entry = pte_to_swp_entry(orig_pte);
page = lookup_swap_cache(entry);
@@ -1682,11 +1705,10 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
page = read_swap_cache_async(entry, vma, address);
if (!page) {
/*
- * Back out if somebody else faulted in this pte while
- * we released the page table lock.
+ * Back out if somebody else faulted in this pte
+ * while we released the pte lock.
*/
- spin_lock(&mm->page_table_lock);
- page_table = pte_offset_map(pmd, address);
+ page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
if (likely(pte_same(*page_table, orig_pte)))
ret = VM_FAULT_OOM;
goto unlock;
@@ -1702,11 +1724,9 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
lock_page(page);
/*
- * Back out if somebody else faulted in this pte while we
- * released the page table lock.
+ * Back out if somebody else already faulted in this pte.
*/
- spin_lock(&mm->page_table_lock);
- page_table = pte_offset_map(pmd, address);
+ page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
if (unlikely(!pte_same(*page_table, orig_pte)))
goto out_nomap;
@@ -1735,7 +1755,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (write_access) {
if (do_wp_page(mm, vma, address,
- page_table, pmd, pte) == VM_FAULT_OOM)
+ page_table, pmd, ptl, pte) == VM_FAULT_OOM)
ret = VM_FAULT_OOM;
goto out;
}
@@ -1744,37 +1764,32 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
update_mmu_cache(vma, address, pte);
lazy_mmu_prot_update(pte);
unlock:
- pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
+ pte_unmap_unlock(page_table, ptl);
out:
return ret;
out_nomap:
- pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
+ pte_unmap_unlock(page_table, ptl);
unlock_page(page);
page_cache_release(page);
return ret;
}
/*
- * We are called with the MM semaphore and page_table_lock
- * spinlock held to protect against concurrent faults in
- * multithreaded programs.
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
*/
static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *page_table, pmd_t *pmd,
int write_access)
{
- struct page *page = ZERO_PAGE(addr);
+ struct page *page;
+ spinlock_t *ptl;
pte_t entry;
- /* Mapping of ZERO_PAGE - vm_page_prot is readonly */
- entry = mk_pte(page, vma->vm_page_prot);
-
if (write_access) {
/* Allocate our own private page. */
pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
if (unlikely(anon_vma_prepare(vma)))
goto oom;
@@ -1782,23 +1797,28 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (!page)
goto oom;
- spin_lock(&mm->page_table_lock);
- page_table = pte_offset_map(pmd, address);
-
- if (!pte_none(*page_table)) {
- page_cache_release(page);
- goto unlock;
- }
- inc_mm_counter(mm, anon_rss);
entry = mk_pte(page, vma->vm_page_prot);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+
+ page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
+ if (!pte_none(*page_table))
+ goto release;
+ inc_mm_counter(mm, anon_rss);
lru_cache_add_active(page);
SetPageReferenced(page);
page_add_anon_rmap(page, vma, address);
} else {
+ /* Map the ZERO_PAGE - vm_page_prot is readonly */
+ page = ZERO_PAGE(address);
+ page_cache_get(page);
+ entry = mk_pte(page, vma->vm_page_prot);
+
+ ptl = &mm->page_table_lock;
+ spin_lock(ptl);
+ if (!pte_none(*page_table))
+ goto release;
inc_mm_counter(mm, file_rss);
page_add_file_rmap(page);
- page_cache_get(page);
}
set_pte_at(mm, address, page_table, entry);
@@ -1807,9 +1827,11 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
update_mmu_cache(vma, address, entry);
lazy_mmu_prot_update(entry);
unlock:
- pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
+ pte_unmap_unlock(page_table, ptl);
return VM_FAULT_MINOR;
+release:
+ page_cache_release(page);
+ goto unlock;
oom:
return VM_FAULT_OOM;
}
@@ -1823,13 +1845,15 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
* As this is called only for pages that do not currently exist, we
* do not need to flush old virtual caches or the TLB.
*
- * This is called with the MM semaphore held and the page table
- * spinlock held. Exit with the spinlock released.
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
*/
static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *page_table, pmd_t *pmd,
int write_access)
{
+ spinlock_t *ptl;
struct page *new_page;
struct address_space *mapping = NULL;
pte_t entry;
@@ -1838,7 +1862,6 @@ static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
int anon = 0;
pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
if (vma->vm_file) {
mapping = vma->vm_file->f_mapping;
@@ -1878,21 +1901,20 @@ static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
anon = 1;
}
- spin_lock(&mm->page_table_lock);
+ page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
/*
* For a file-backed vma, someone could have truncated or otherwise
* invalidated this page. If unmap_mapping_range got called,
* retry getting the page.
*/
if (mapping && unlikely(sequence != mapping->truncate_count)) {
- spin_unlock(&mm->page_table_lock);
+ pte_unmap_unlock(page_table, ptl);
page_cache_release(new_page);
cond_resched();
sequence = mapping->truncate_count;
smp_rmb();
goto retry;
}
- page_table = pte_offset_map(pmd, address);
/*
* This silly early PAGE_DIRTY setting removes a race
@@ -1929,8 +1951,7 @@ static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
update_mmu_cache(vma, address, entry);
lazy_mmu_prot_update(entry);
unlock:
- pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
+ pte_unmap_unlock(page_table, ptl);
return ret;
oom:
page_cache_release(new_page);
@@ -1941,6 +1962,10 @@ static int do_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
* Fault of a previously existing named mapping. Repopulate the pte
* from the encoded file_pte if possible. This enables swappable
* nonlinear vmas.
+ *
+ * We enter with non-exclusive mmap_sem (to exclude vma changes,
+ * but allow concurrent faults), and pte mapped but not yet locked.
+ * We return with mmap_sem still held, but pte unmapped and unlocked.
*/
static int do_file_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *page_table, pmd_t *pmd,
@@ -1949,8 +1974,8 @@ static int do_file_page(struct mm_struct *mm, struct vm_area_struct *vma,
pgoff_t pgoff;
int err;
- pte_unmap(page_table);
- spin_unlock(&mm->page_table_lock);
+ if (!pte_unmap_same(mm, page_table, orig_pte))
+ return VM_FAULT_MINOR;
if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
/*
@@ -1989,8 +2014,8 @@ static inline int handle_pte_fault(struct mm_struct *mm,
pte_t *pte, pmd_t *pmd, int write_access)
{
pte_t entry;
+ spinlock_t *ptl;
- spin_lock(&mm->page_table_lock);
entry = *pte;
if (!pte_present(entry)) {
if (pte_none(entry)) {
@@ -2007,17 +2032,22 @@ static inline int handle_pte_fault(struct mm_struct *mm,
pte, pmd, write_access, entry);
}
+ ptl = &mm->page_table_lock;
+ spin_lock(ptl);
+ if (unlikely(!pte_same(*pte, entry)))
+ goto unlock;
if (write_access) {
if (!pte_write(entry))
- return do_wp_page(mm, vma, address, pte, pmd, entry);
+ return do_wp_page(mm, vma, address,
+ pte, pmd, ptl, entry);
entry = pte_mkdirty(entry);
}
entry = pte_mkyoung(entry);
ptep_set_access_flags(vma, address, pte, entry, write_access);
update_mmu_cache(vma, address, entry);
lazy_mmu_prot_update(entry);
- pte_unmap(pte);
- spin_unlock(&mm->page_table_lock);
+unlock:
+ pte_unmap_unlock(pte, ptl);
return VM_FAULT_MINOR;
}