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-rw-r--r--mm/zsmalloc.c61
1 files changed, 59 insertions, 2 deletions
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 5105b9b66653..08def3a0d200 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -54,6 +54,7 @@
#include <linux/mount.h>
#include <linux/pseudo_fs.h>
#include <linux/migrate.h>
+#include <linux/wait.h>
#include <linux/pagemap.h>
#include <linux/fs.h>
@@ -268,6 +269,10 @@ struct zs_pool {
#ifdef CONFIG_COMPACTION
struct inode *inode;
struct work_struct free_work;
+ /* A wait queue for when migration races with async_free_zspage() */
+ struct wait_queue_head migration_wait;
+ atomic_long_t isolated_pages;
+ bool destroying;
#endif
};
@@ -1874,6 +1879,19 @@ static void putback_zspage_deferred(struct zs_pool *pool,
}
+static inline void zs_pool_dec_isolated(struct zs_pool *pool)
+{
+ VM_BUG_ON(atomic_long_read(&pool->isolated_pages) <= 0);
+ atomic_long_dec(&pool->isolated_pages);
+ /*
+ * There's no possibility of racing, since wait_for_isolated_drain()
+ * checks the isolated count under &class->lock after enqueuing
+ * on migration_wait.
+ */
+ if (atomic_long_read(&pool->isolated_pages) == 0 && pool->destroying)
+ wake_up_all(&pool->migration_wait);
+}
+
static void replace_sub_page(struct size_class *class, struct zspage *zspage,
struct page *newpage, struct page *oldpage)
{
@@ -1943,6 +1961,7 @@ static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
*/
if (!list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
get_zspage_mapping(zspage, &class_idx, &fullness);
+ atomic_long_inc(&pool->isolated_pages);
remove_zspage(class, zspage, fullness);
}
@@ -2042,8 +2061,16 @@ static int zs_page_migrate(struct address_space *mapping, struct page *newpage,
* Page migration is done so let's putback isolated zspage to
* the list if @page is final isolated subpage in the zspage.
*/
- if (!is_zspage_isolated(zspage))
+ if (!is_zspage_isolated(zspage)) {
+ /*
+ * We cannot race with zs_destroy_pool() here because we wait
+ * for isolation to hit zero before we start destroying.
+ * Also, we ensure that everyone can see pool->destroying before
+ * we start waiting.
+ */
putback_zspage_deferred(pool, class, zspage);
+ zs_pool_dec_isolated(pool);
+ }
reset_page(page);
put_page(page);
@@ -2094,8 +2121,8 @@ static void zs_page_putback(struct page *page)
* so let's defer.
*/
putback_zspage_deferred(pool, class, zspage);
+ zs_pool_dec_isolated(pool);
}
-
spin_unlock(&class->lock);
}
@@ -2118,8 +2145,36 @@ static int zs_register_migration(struct zs_pool *pool)
return 0;
}
+static bool pool_isolated_are_drained(struct zs_pool *pool)
+{
+ return atomic_long_read(&pool->isolated_pages) == 0;
+}
+
+/* Function for resolving migration */
+static void wait_for_isolated_drain(struct zs_pool *pool)
+{
+
+ /*
+ * We're in the process of destroying the pool, so there are no
+ * active allocations. zs_page_isolate() fails for completely free
+ * zspages, so we need only wait for the zs_pool's isolated
+ * count to hit zero.
+ */
+ wait_event(pool->migration_wait,
+ pool_isolated_are_drained(pool));
+}
+
static void zs_unregister_migration(struct zs_pool *pool)
{
+ pool->destroying = true;
+ /*
+ * We need a memory barrier here to ensure global visibility of
+ * pool->destroying. Thus pool->isolated pages will either be 0 in which
+ * case we don't care, or it will be > 0 and pool->destroying will
+ * ensure that we wake up once isolation hits 0.
+ */
+ smp_mb();
+ wait_for_isolated_drain(pool); /* This can block */
flush_work(&pool->free_work);
iput(pool->inode);
}
@@ -2357,6 +2412,8 @@ struct zs_pool *zs_create_pool(const char *name)
if (!pool->name)
goto err;
+ init_waitqueue_head(&pool->migration_wait);
+
if (create_cache(pool))
goto err;