*/
static void lock_zspage(struct zspage *zspage)
{
- struct page *page = get_first_page(zspage);
+ struct page *curr_page, *page;
- do {
- lock_page(page);
- } while ((page = get_next_page(page)) != NULL);
+ /*
+ * Pages we haven't locked yet can be migrated off the list while we're
+ * trying to lock them, so we need to be careful and only attempt to
+ * lock each page under migrate_read_lock(). Otherwise, the page we lock
+ * may no longer belong to the zspage. This means that we may wait for
+ * the wrong page to unlock, so we must take a reference to the page
+ * prior to waiting for it to unlock outside migrate_read_lock().
+ */
+ while (1) {
+ migrate_read_lock(zspage);
+ page = get_first_page(zspage);
+ if (trylock_page(page))
+ break;
+ get_page(page);
+ migrate_read_unlock(zspage);
+ wait_on_page_locked(page);
+ put_page(page);
+ }
+
+ curr_page = page;
+ while ((page = get_next_page(curr_page))) {
+ if (trylock_page(page)) {
+ curr_page = page;
+ } else {
+ get_page(page);
+ migrate_read_unlock(zspage);
+ wait_on_page_locked(page);
+ put_page(page);
+ migrate_read_lock(zspage);
+ }
+ }
+ migrate_read_unlock(zspage);
}
static int zs_init_fs_context(struct fs_context *fc)
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.
+ * Checking pool->destroying must happen after atomic_long_dec()
+ * for pool->isolated_pages above. Paired with the smp_mb() in
+ * zs_unregister_migration().
*/
+ smp_mb__after_atomic();
if (atomic_long_read(&pool->isolated_pages) == 0 && pool->destroying)
wake_up_all(&pool->migration_wait);
}