We reorganize the page_referenced and try_to_unmap code to determine
explicitly if mapping->i_mmap_mutex needs to be acquired. This allows
us to acquire the mutex for multiple pages in batch. We can call
__page_referenced or __try_to_unmap with the mutex already acquired so
the mutex doesn't have to be acquired multiple times.
Tim
---
Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
---
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index fd07c45..f1320b1 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -156,8 +156,11 @@ static inline void page_dup_rmap(struct page *page)
/*
* Called from mm/vmscan.c to handle paging out
*/
-int page_referenced(struct page *, int is_locked,
- struct mem_cgroup *memcg, unsigned long *vm_flags);
+int needs_page_mmap_mutex(struct page *page);
+int page_referenced(struct page *, int is_locked, struct mem_cgroup *memcg,
+ unsigned long *vm_flags);
+int __page_referenced(struct page *, int is_locked, struct mem_cgroup *memcg,
+ unsigned long *vm_flags);
int page_referenced_one(struct page *, struct vm_area_struct *,
unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);
@@ -176,6 +179,7 @@ enum ttu_flags {
bool is_vma_temporary_stack(struct vm_area_struct *vma);
int try_to_unmap(struct page *, enum ttu_flags flags);
+int __try_to_unmap(struct page *, enum ttu_flags flags);
int try_to_unmap_one(struct page *, struct vm_area_struct *,
unsigned long address, enum ttu_flags flags);
diff --git a/mm/rmap.c b/mm/rmap.c
index 5b5ad58..8be1799 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -843,8 +843,7 @@ static int page_referenced_file(struct page *page,
* so we can safely take mapping->i_mmap_mutex.
*/
BUG_ON(!PageLocked(page));
-
- mutex_lock(&mapping->i_mmap_mutex);
+ BUG_ON(!mutex_is_locked(&mapping->i_mmap_mutex));
/*
* i_mmap_mutex does not stabilize mapcount at all, but mapcount
@@ -869,21 +868,15 @@ static int page_referenced_file(struct page *page,
break;
}
- mutex_unlock(&mapping->i_mmap_mutex);
return referenced;
}
-/**
- * page_referenced - test if the page was referenced
- * @page: the page to test
- * @is_locked: caller holds lock on the page
- * @memcg: target memory cgroup
- * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
- *
- * Quick test_and_clear_referenced for all mappings to a page,
- * returns the number of ptes which referenced the page.
- */
-int page_referenced(struct page *page,
+int needs_page_mmap_mutex(struct page *page)
+{
+ return page->mapping && !PageKsm(page) && !PageAnon(page);
+}
+
+int __page_referenced(struct page *page,
int is_locked,
struct mem_cgroup *memcg,
unsigned long *vm_flags)
@@ -919,6 +912,32 @@ out:
return referenced;
}
+/**
+ * page_referenced - test if the page was referenced
+ * @page: the page to test
+ * @is_locked: caller holds lock on the page
+ * @memcg: target memory cgroup
+ * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
+ *
+ * Quick test_and_clear_referenced for all mappings to a page,
+ * returns the number of ptes which referenced the page.
+ */
+int page_referenced(struct page *page,
+ int is_locked,
+ struct mem_cgroup *memcg,
+ unsigned long *vm_flags)
+{
+ int result, needs_lock;
+
+ needs_lock = needs_page_mmap_mutex(page);
+ if (needs_lock)
+ mutex_lock(&page->mapping->i_mmap_mutex);
+ result = __page_referenced(page, is_locked, memcg, vm_flags);
+ if (needs_lock)
+ mutex_unlock(&page->mapping->i_mmap_mutex);
+ return result;
+}
+
static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
unsigned long address)
{
@@ -1560,7 +1579,7 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
unsigned long max_nl_size = 0;
unsigned int mapcount;
- mutex_lock(&mapping->i_mmap_mutex);
+ BUG_ON(!mutex_is_locked(&mapping->i_mmap_mutex));
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
unsigned long address = vma_address(page, vma);
if (address == -EFAULT)
@@ -1640,7 +1659,24 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
vma->vm_private_data = NULL;
out:
- mutex_unlock(&mapping->i_mmap_mutex);
+ return ret;
+}
+
+int __try_to_unmap(struct page *page, enum ttu_flags flags)
+{
+ int ret;
+
+ BUG_ON(!PageLocked(page));
+ VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
+
+ if (unlikely(PageKsm(page)))
+ ret = try_to_unmap_ksm(page, flags);
+ else if (PageAnon(page))
+ ret = try_to_unmap_anon(page, flags);
+ else
+ ret = try_to_unmap_file(page, flags);
+ if (ret != SWAP_MLOCK && !page_mapped(page))
+ ret = SWAP_SUCCESS;
return ret;
}
@@ -1660,20 +1696,27 @@ out:
*/
int try_to_unmap(struct page *page, enum ttu_flags flags)
{
- int ret;
+ int result, needs_lock;
+
+ needs_lock = needs_page_mmap_mutex(page);
+ if (needs_lock)
+ mutex_lock(&page->mapping->i_mmap_mutex);
+ result = __try_to_unmap(page, flags);
+ if (needs_lock)
+ mutex_unlock(&page->mapping->i_mmap_mutex);
+ return result;
+}
- BUG_ON(!PageLocked(page));
- VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
+static int __try_to_munlock(struct page *page)
+{
+ VM_BUG_ON(!PageLocked(page) || PageLRU(page));
if (unlikely(PageKsm(page)))
- ret = try_to_unmap_ksm(page, flags);
+ return try_to_unmap_ksm(page, TTU_MUNLOCK);
else if (PageAnon(page))
- ret = try_to_unmap_anon(page, flags);
+ return try_to_unmap_anon(page, TTU_MUNLOCK);
else
- ret = try_to_unmap_file(page, flags);
- if (ret != SWAP_MLOCK && !page_mapped(page))
- ret = SWAP_SUCCESS;
- return ret;
+ return try_to_unmap_file(page, TTU_MUNLOCK);
}
/**
@@ -1693,14 +1736,15 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
*/
int try_to_munlock(struct page *page)
{
- VM_BUG_ON(!PageLocked(page) || PageLRU(page));
-
- if (unlikely(PageKsm(page)))
- return try_to_unmap_ksm(page, TTU_MUNLOCK);
- else if (PageAnon(page))
- return try_to_unmap_anon(page, TTU_MUNLOCK);
- else
- return try_to_unmap_file(page, TTU_MUNLOCK);
+ int result, needs_lock;
+
+ needs_lock = needs_page_mmap_mutex(page);
+ if (needs_lock)
+ mutex_lock(&page->mapping->i_mmap_mutex);
+ result = __try_to_munlock(page);
+ if (needs_lock)
+ mutex_unlock(&page->mapping->i_mmap_mutex);
+ return result;
}
void __put_anon_vma(struct anon_vma *anon_vma)
--
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