/*
* Add a shrinker callback to be called from the vm.
*/
-int register_shrinker(struct shrinker *shrinker)
+int prealloc_shrinker(struct shrinker *shrinker)
{
size_t size = sizeof(*shrinker->nr_deferred);
shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
if (!shrinker->nr_deferred)
return -ENOMEM;
+ return 0;
+}
+
+void free_prealloced_shrinker(struct shrinker *shrinker)
+{
+ kfree(shrinker->nr_deferred);
+ shrinker->nr_deferred = NULL;
+}
+void register_shrinker_prepared(struct shrinker *shrinker)
+{
down_write(&shrinker_rwsem);
list_add_tail(&shrinker->list, &shrinker_list);
up_write(&shrinker_rwsem);
+}
+
+int register_shrinker(struct shrinker *shrinker)
+{
+ int err = prealloc_shrinker(shrinker);
+
+ if (err)
+ return err;
+ register_shrinker_prepared(shrinker);
return 0;
}
EXPORT_SYMBOL(register_shrinker);
*/
void unregister_shrinker(struct shrinker *shrinker)
{
+ if (!shrinker->nr_deferred)
+ return;
down_write(&shrinker_rwsem);
list_del(&shrinker->list);
up_write(&shrinker_rwsem);
kfree(shrinker->nr_deferred);
+ shrinker->nr_deferred = NULL;
}
EXPORT_SYMBOL(unregister_shrinker);
sc.nid = 0;
freed += do_shrink_slab(&sc, shrinker, nr_scanned, nr_eligible);
+ /*
+ * Bail out if someone want to register a new shrinker to
+ * prevent the regsitration from being stalled for long periods
+ * by parallel ongoing shrinking.
+ */
+ if (rwsem_is_contended(&shrinker_rwsem)) {
+ freed = freed ? : 1;
+ break;
+ }
}
up_read(&shrinker_rwsem);
if (PageDirty(page)) {
struct address_space *mapping;
+ bool migrate_dirty;
/*
* Only pages without mappings or that have a
* ->migratepage callback are possible to migrate
- * without blocking
+ * without blocking. However, we can be racing with
+ * truncation so it's necessary to lock the page
+ * to stabilise the mapping as truncation holds
+ * the page lock until after the page is removed
+ * from the page cache.
*/
+ if (!trylock_page(page))
+ return ret;
+
mapping = page_mapping(page);
- if (mapping && !mapping->a_ops->migratepage)
+ migrate_dirty = !mapping || mapping->a_ops->migratepage;
+ unlock_page(page);
+ if (!migrate_dirty)
return ret;
}
}
if (stat.nr_writeback && stat.nr_writeback == nr_taken)
set_bit(PGDAT_WRITEBACK, &pgdat->flags);
+ /*
+ * If dirty pages are scanned that are not queued for IO, it
+ * implies that flushers are not doing their job. This can
+ * happen when memory pressure pushes dirty pages to the end of
+ * the LRU before the dirty limits are breached and the dirty
+ * data has expired. It can also happen when the proportion of
+ * dirty pages grows not through writes but through memory
+ * pressure reclaiming all the clean cache. And in some cases,
+ * the flushers simply cannot keep up with the allocation
+ * rate. Nudge the flusher threads in case they are asleep.
+ */
+ if (stat.nr_unqueued_dirty == nr_taken)
+ wakeup_flusher_threads(WB_REASON_VMSCAN);
+
/*
* Legacy memcg will stall in page writeback so avoid forcibly
* stalling here.
if (stat.nr_dirty && stat.nr_dirty == stat.nr_congested)
set_bit(PGDAT_CONGESTED, &pgdat->flags);
- /*
- * If dirty pages are scanned that are not queued for IO, it
- * implies that flushers are not doing their job. This can
- * happen when memory pressure pushes dirty pages to the end of
- * the LRU before the dirty limits are breached and the dirty
- * data has expired. It can also happen when the proportion of
- * dirty pages grows not through writes but through memory
- * pressure reclaiming all the clean cache. And in some cases,
- * the flushers simply cannot keep up with the allocation
- * rate. Nudge the flusher threads in case they are asleep, but
- * also allow kswapd to start writing pages during reclaim.
- */
- if (stat.nr_unqueued_dirty == nr_taken) {
- wakeup_flusher_threads(WB_REASON_VMSCAN);
+ /* Allow kswapd to start writing pages during reclaim. */
+ if (stat.nr_unqueued_dirty == nr_taken)
set_bit(PGDAT_DIRTY, &pgdat->flags);
- }
/*
* If kswapd scans pages marked marked for immediate
*/
int page_evictable(struct page *page)
{
- return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
+ int ret;
+
+ /* Prevent address_space of inode and swap cache from being freed */
+ rcu_read_lock();
+ ret = !mapping_unevictable(page_mapping(page)) && !PageMlocked(page);
+ rcu_read_unlock();
+ return ret;
}
#ifdef CONFIG_SHMEM