Use count/scan objects shrinking interface

Move to the more recent interfaces for counting and scanning cached
objects to shrink.

Signed-off-by: Zach Brown <zab@versity.com>
Signed-off-by: Auke Kok <auke.kok@versity.com>

kmod/src/Makefile

@@ -25,6 +25,7 @@ scoutfs-y +=			\
 	inode.o			\
 	ioctl.o			\
 	item.o			\
+	kernelcompat.o		\
 	lock.o			\
 	lock_server.o		\
 	msg.o			\

kmod/src/Makefile.kernelcompat

@@ -130,3 +130,12 @@ endif
 ifneq (,$(shell grep 'bi_status' include/linux/blk_types.h))
 ccflags-y += -DKC_BIO_BI_STATUS
 endif
+
+#
+# v3.11-8765-ga0b02131c5fc
+#
+# Remove the old ->shrink() API, ->{scan,count}_objects is preferred.
+#
+ifneq (,$(shell grep '(*shrink)' include/linux/shrinker.h))
+ccflags-y += -DKC_SHRINKER_SHRINK
+endif

kmod/src/block.c

@@ -31,6 +31,7 @@
 #include "scoutfs_trace.h"
 #include "alloc.h"
 #include "triggers.h"
+#include "util.h"
 
 /*
  * The scoutfs block cache manages metadata blocks that can be larger
@@ -58,7 +59,7 @@ struct block_info {
 	atomic64_t access_counter;
 	struct rhashtable ht;
 	wait_queue_head_t waitq;
-	struct shrinker shrinker;
+	KC_DEFINE_SHRINKER(shrinker);
 	struct work_struct free_work;
 	struct llist_head free_llist;
 };
@@ -1070,6 +1071,16 @@ u64 scoutfs_block_writer_dirty_bytes(struct super_block *sb,
 	return wri->nr_dirty_blocks * SCOUTFS_BLOCK_LG_SIZE;
 }
 
+static unsigned long block_count_objects(struct shrinker *shrink, struct shrink_control *sc)
+{
+	struct block_info *binf = KC_SHRINKER_CONTAINER_OF(shrink, struct block_info);
+	struct super_block *sb = binf->sb;
+
+	scoutfs_inc_counter(sb, block_cache_count_objects);
+
+	return shrinker_min_long(atomic_read(&binf->total_inserted));
+}
+
 /*
  * Remove a number of cached blocks that haven't been used recently.
  *
@@ -1090,24 +1101,18 @@ u64 scoutfs_block_writer_dirty_bytes(struct super_block *sb,
  * atomically remove blocks when the only references are ours and the
  * hash table.
  */
-static int block_shrink(struct shrinker *shrink, struct shrink_control *sc)
+static unsigned long block_scan_objects(struct shrinker *shrink, struct shrink_control *sc)
 {
-	struct block_info *binf = container_of(shrink, struct block_info,
-					       shrinker);
+	struct block_info *binf = KC_SHRINKER_CONTAINER_OF(shrink, struct block_info);
 	struct super_block *sb = binf->sb;
 	struct rhashtable_iter iter;
 	struct block_private *bp;
 	bool stop = false;
-	unsigned long nr;
+	unsigned long freed = 0;
+	unsigned long nr = sc->nr_to_scan;
 	u64 recently;
 
-	nr = sc->nr_to_scan;
-	if (nr == 0)
-		goto out;
-
-	scoutfs_inc_counter(sb, block_cache_shrink);
-
-	nr = DIV_ROUND_UP(nr, SCOUTFS_BLOCK_LG_PAGES_PER);
+	scoutfs_inc_counter(sb, block_cache_scan_objects);
 
 	recently = accessed_recently(binf);
 	rhashtable_walk_enter(&binf->ht, &iter);
@@ -1152,6 +1157,7 @@ static int block_shrink(struct shrinker *shrink, struct shrink_control *sc)
 			if (block_remove_solo(sb, bp)) {
 				scoutfs_inc_counter(sb, block_cache_shrink_remove);
 				TRACE_BLOCK(shrink, bp);
+				freed++;
 				nr--;
 			}
 			block_put(sb, bp);
@@ -1160,12 +1166,11 @@ static int block_shrink(struct shrinker *shrink, struct shrink_control *sc)
 
 	rhashtable_walk_stop(&iter);
 	rhashtable_walk_exit(&iter);
-out:
+
 	if (stop)
-		return -1;
+		return SHRINK_STOP;
 	else
-		return min_t(u64, INT_MAX,
-			     (u64)atomic_read(&binf->total_inserted) * SCOUTFS_BLOCK_LG_PAGES_PER);
+		return freed;
 }
 
 struct sm_block_completion {
@@ -1291,9 +1296,9 @@ int scoutfs_block_setup(struct super_block *sb)
 	atomic_set(&binf->total_inserted, 0);
 	atomic64_set(&binf->access_counter, 0);
 	init_waitqueue_head(&binf->waitq);
-	binf->shrinker.shrink = block_shrink;
-	binf->shrinker.seeks = DEFAULT_SEEKS;
-	register_shrinker(&binf->shrinker);
+	KC_INIT_SHRINKER_FUNCS(&binf->shrinker, block_count_objects,
+			       block_scan_objects);
+	KC_REGISTER_SHRINKER(&binf->shrinker);
 	INIT_WORK(&binf->free_work, block_free_work);
 	init_llist_head(&binf->free_llist);
 
@@ -1313,7 +1318,7 @@ void scoutfs_block_destroy(struct super_block *sb)
 	struct block_info *binf = SCOUTFS_SB(sb)->block_info;
 
 	if (binf) {
-		unregister_shrinker(&binf->shrinker);
+		KC_UNREGISTER_SHRINKER(&binf->shrinker);
 		block_remove_all(sb);
 		flush_work(&binf->free_work);
 		rhashtable_destroy(&binf->ht);

kmod/src/counters.h

@@ -30,6 +30,8 @@
 	EXPAND_COUNTER(block_cache_free)			\
 	EXPAND_COUNTER(block_cache_free_work)			\
 	EXPAND_COUNTER(block_cache_remove_stale)		\
+	EXPAND_COUNTER(block_cache_count_objects)		\
+	EXPAND_COUNTER(block_cache_scan_objects)		\
 	EXPAND_COUNTER(block_cache_shrink)			\
 	EXPAND_COUNTER(block_cache_shrink_next)			\
 	EXPAND_COUNTER(block_cache_shrink_recent)		\
@@ -88,6 +90,8 @@
 	EXPAND_COUNTER(forest_read_items)			\
 	EXPAND_COUNTER(forest_roots_next_hint)			\
 	EXPAND_COUNTER(forest_set_bloom_bits)			\
+	EXPAND_COUNTER(item_cache_count_objects)		\
+	EXPAND_COUNTER(item_cache_scan_objects)			\
 	EXPAND_COUNTER(item_clear_dirty)			\
 	EXPAND_COUNTER(item_create)				\
 	EXPAND_COUNTER(item_delete)				\
@@ -121,6 +125,7 @@
 	EXPAND_COUNTER(item_update)				\
 	EXPAND_COUNTER(item_write_dirty)			\
 	EXPAND_COUNTER(lock_alloc)				\
+	EXPAND_COUNTER(lock_count_objects)			\
 	EXPAND_COUNTER(lock_free)				\
 	EXPAND_COUNTER(lock_grant_request)			\
 	EXPAND_COUNTER(lock_grant_response)			\
@@ -134,6 +139,7 @@
 	EXPAND_COUNTER(lock_lock_error)				\
 	EXPAND_COUNTER(lock_nonblock_eagain)			\
 	EXPAND_COUNTER(lock_recover_request)			\
+	EXPAND_COUNTER(lock_scan_objects)			\
 	EXPAND_COUNTER(lock_shrink_attempted)			\
 	EXPAND_COUNTER(lock_shrink_aborted)			\
 	EXPAND_COUNTER(lock_shrink_work)			\

kmod/src/item.c

@@ -27,6 +27,7 @@
 #include "trans.h"
 #include "counters.h"
 #include "scoutfs_trace.h"
+#include "util.h"
 
 /*
  * The item cache maintains a consistent view of items that are read
@@ -76,7 +77,7 @@ struct item_cache_info {
 	/* almost always read, barely written */
 	struct super_block *sb;
 	struct item_percpu_pages __percpu *pcpu_pages;
-	struct shrinker shrinker;
+	KC_DEFINE_SHRINKER(shrinker);
 	struct notifier_block notifier;
 
 	/* often walked, but per-cpu refs are fast path */
@@ -2530,27 +2531,35 @@ retry:
 	put_pg(sb, right);
 }
 
+static unsigned long item_cache_count_objects(struct shrinker *shrink,
+					      struct shrink_control *sc)
+{
+	struct item_cache_info *cinf = KC_SHRINKER_CONTAINER_OF(shrink, struct item_cache_info);
+	struct super_block *sb = cinf->sb;
+
+	scoutfs_inc_counter(sb, item_cache_count_objects);
+
+	return shrinker_min_long(cinf->lru_pages);
+}
+
 /*
  * Shrink the size the item cache.  We're operating against the fast
  * path lock ordering and we skip pages if we can't acquire locks.  We
  * can run into dirty pages or pages with items that weren't visible to
  * the earliest active reader which must be skipped.
  */
-static int item_lru_shrink(struct shrinker *shrink,
-			   struct shrink_control *sc)
+static unsigned long item_cache_scan_objects(struct shrinker *shrink,
+					     struct shrink_control *sc)
 {
-	struct item_cache_info *cinf = container_of(shrink,
-						    struct item_cache_info,
-						    shrinker);
+	struct item_cache_info *cinf = KC_SHRINKER_CONTAINER_OF(shrink, struct item_cache_info);
 	struct super_block *sb = cinf->sb;
 	struct cached_page *tmp;
 	struct cached_page *pg;
+	unsigned long freed = 0;
 	u64 first_reader_seq;
-	int nr;
+	int nr = sc->nr_to_scan;
 
-	if (sc->nr_to_scan == 0)
-		goto out;
-	nr = sc->nr_to_scan;
+	scoutfs_inc_counter(sb, item_cache_scan_objects);
 
 	/* can't invalidate pages with items that weren't visible to first reader */
 	first_reader_seq = first_active_reader_seq(cinf);
@@ -2582,6 +2591,7 @@ static int item_lru_shrink(struct shrinker *shrink,
 		rbtree_erase(&pg->node, &cinf->pg_root);
 		invalidate_pcpu_page(pg);
 		write_unlock(&pg->rwlock);
+		freed++;
 
 		put_pg(sb, pg);
 
@@ -2591,8 +2601,8 @@ static int item_lru_shrink(struct shrinker *shrink,
 
 	write_unlock(&cinf->rwlock);
 	spin_unlock(&cinf->lru_lock);
-out:
-	return min_t(unsigned long, cinf->lru_pages, INT_MAX);
+
+	return freed;
 }
 
 static int item_cpu_callback(struct notifier_block *nfb,
@@ -2638,9 +2648,9 @@ int scoutfs_item_setup(struct super_block *sb)
 	for_each_possible_cpu(cpu)
 		init_pcpu_pages(cinf, cpu);
 
-	cinf->shrinker.shrink = item_lru_shrink;
-	cinf->shrinker.seeks = DEFAULT_SEEKS;
-	register_shrinker(&cinf->shrinker);
+	KC_INIT_SHRINKER_FUNCS(&cinf->shrinker, item_cache_count_objects,
+			       item_cache_scan_objects);
+	KC_REGISTER_SHRINKER(&cinf->shrinker);
         cinf->notifier.notifier_call = item_cpu_callback;
         register_hotcpu_notifier(&cinf->notifier);
 
@@ -2663,7 +2673,7 @@ void scoutfs_item_destroy(struct super_block *sb)
 		BUG_ON(!list_empty(&cinf->active_list));
 
 		unregister_hotcpu_notifier(&cinf->notifier);
-		unregister_shrinker(&cinf->shrinker);
+		KC_UNREGISTER_SHRINKER(&cinf->shrinker);
 
 		for_each_possible_cpu(cpu)
 			drop_pcpu_pages(sb, cinf, cpu);

kmod/src/kernelcompat.c

@@ -0,0 +1,30 @@
+
+#include "kernelcompat.h"
+
+#ifdef KC_SHRINKER_SHRINK
+#include <linux/shrinker.h>
+/*
+ * If a target doesn't have that .{count,scan}_objects() interface then
+ * we have a .shrink() helper that performs the shrink work in terms of
+ * count/scan.
+ */
+int kc_shrink_wrapper_fn(struct shrinker *shrink, struct shrink_control *sc)
+{
+	struct kc_shrinker_wrapper *wrapper = container_of(shrink, struct kc_shrinker_wrapper, shrink);
+	unsigned long nr;
+	unsigned long rc;
+
+	if (sc->nr_to_scan != 0) {
+		rc = wrapper->scan_objects(shrink, sc);
+		/* translate magic values to the equivalent for older kernels */
+		if (rc == SHRINK_STOP)
+			return -1;
+		else if (rc == SHRINK_EMPTY)
+			return 0;
+	}
+
+	nr = wrapper->count_objects(shrink, sc);
+
+	return min_t(unsigned long, nr, INT_MAX);
+}
+#endif

kmod/src/kernelcompat.h

@@ -167,4 +167,48 @@ do {					\
 #define kc_bio_get_errno(bio)			({ (int)((void)(bio), _error_arg); })
 #endif
 
+#ifndef KC_SHRINKER_SHRINK
+
+#define KC_DEFINE_SHRINKER(name) struct shrinker name
+#define KC_INIT_SHRINKER_FUNCS(name, countfn, scanfn) do {	\
+	__typeof__(name) _shrink = (name);			\
+	_shrink->count_objects = (countfn);			\
+	_shrink->scan_objects = (scanfn);			\
+	_shrink->seeks = DEFAULT_SEEKS;			\
+} while (0)
+
+#define KC_SHRINKER_CONTAINER_OF(ptr, type) container_of(ptr, type, shrinker)
+#define KC_REGISTER_SHRINKER(ptr) (register_shrinker(ptr))
+#define KC_UNREGISTER_SHRINKER(ptr) (unregister_shrinker(ptr))
+#define KC_SHRINKER_FN(ptr) (ptr)
+#else
+
+#include <linux/shrinker.h>
+#ifndef SHRINK_STOP
+#define SHRINK_STOP (~0UL)
+#define SHRINK_EMPTY (~0UL - 1)
+#endif
+
+int kc_shrink_wrapper_fn(struct shrinker *shrink, struct shrink_control *sc);
+struct kc_shrinker_wrapper {
+	unsigned long (*count_objects)(struct shrinker *, struct shrink_control *sc);
+	unsigned long (*scan_objects)(struct shrinker *, struct shrink_control *sc);
+	struct shrinker shrink;
+};
+
+#define KC_DEFINE_SHRINKER(name) struct kc_shrinker_wrapper name;
+#define KC_INIT_SHRINKER_FUNCS(name, countfn, scanfn) do {	\
+	struct kc_shrinker_wrapper *_wrap = (name);		\
+	_wrap->count_objects = (countfn);			\
+	_wrap->scan_objects = (scanfn);				\
+	_wrap->shrink.shrink = kc_shrink_wrapper_fn;		\
+	_wrap->shrink.seeks = DEFAULT_SEEKS;			\
+} while (0)
+#define KC_SHRINKER_CONTAINER_OF(ptr, type) container_of(container_of(ptr, struct kc_shrinker_wrapper, shrink), type, shrinker)
+#define KC_REGISTER_SHRINKER(ptr) (register_shrinker(ptr.shrink))
+#define KC_UNREGISTER_SHRINKER(ptr) (unregister_shrinker(ptr.shrink))
+#define KC_SHRINKER_FN(ptr) (ptr.shrink)
+
+#endif /* KC_SHRINKER_SHRINK */
+
 #endif

kmod/src/lock.c

@@ -35,6 +35,7 @@
 #include "xattr.h"
 #include "item.h"
 #include "omap.h"
+#include "util.h"
 
 /*
  * scoutfs uses a lock service to manage item cache consistency between
@@ -76,7 +77,7 @@ struct lock_info {
 	bool unmounting;
 	struct rb_root lock_tree;
 	struct rb_root lock_range_tree;
-	struct shrinker shrinker;
+	KC_DEFINE_SHRINKER(shrinker);
 	struct list_head lru_list;
 	unsigned long long lru_nr;
 	struct workqueue_struct *workq;
@@ -1400,6 +1401,17 @@ static void lock_shrink_worker(struct work_struct *work)
 	}
 }
 
+static unsigned long lock_count_objects(struct shrinker *shrink,
+					struct shrink_control *sc)
+{
+	struct lock_info *linfo = KC_SHRINKER_CONTAINER_OF(shrink, struct lock_info);
+	struct super_block *sb = linfo->sb;
+
+	scoutfs_inc_counter(sb, lock_count_objects);
+
+	return shrinker_min_long(linfo->lru_nr);
+}
+
 /*
  * Start the shrinking process for locks on the lru.  If a lock is on
  * the lru then it can't have any active users.  We don't want to block
@@ -1412,21 +1424,18 @@ static void lock_shrink_worker(struct work_struct *work)
  * mode which will prevent the lock from being freed when the null
  * response arrives.
  */
-static int scoutfs_lock_shrink(struct shrinker *shrink,
-			       struct shrink_control *sc)
+static unsigned long lock_scan_objects(struct shrinker *shrink,
+				       struct shrink_control *sc)
 {
-	struct lock_info *linfo = container_of(shrink, struct lock_info,
-					       shrinker);
+	struct lock_info *linfo = KC_SHRINKER_CONTAINER_OF(shrink, struct lock_info);
 	struct super_block *sb = linfo->sb;
 	struct scoutfs_lock *lock;
 	struct scoutfs_lock *tmp;
-	unsigned long nr;
+	unsigned long freed = 0;
+	unsigned long nr = sc->nr_to_scan;
 	bool added = false;
-	int ret;
 
-	nr = sc->nr_to_scan;
-	if (nr == 0)
-		goto out;
+	scoutfs_inc_counter(sb, lock_scan_objects);
 
 	spin_lock(&linfo->lock);
 
@@ -1444,6 +1453,7 @@ restart:
 		lock->request_pending = 1;
 		list_add_tail(&lock->shrink_head, &linfo->shrink_list);
 		added = true;
+		freed++;
 
 		scoutfs_inc_counter(sb, lock_shrink_attempted);
 		trace_scoutfs_lock_shrink(sb, lock);
@@ -1458,10 +1468,8 @@ restart:
 	if (added)
 		queue_work(linfo->workq, &linfo->shrink_work);
 
-out:
-	ret = min_t(unsigned long, linfo->lru_nr, INT_MAX);
-	trace_scoutfs_lock_shrink_exit(sb, sc->nr_to_scan, ret);
-	return ret;
+	trace_scoutfs_lock_shrink_exit(sb, sc->nr_to_scan, freed);
+	return freed;
 }
 
 void scoutfs_free_unused_locks(struct super_block *sb)
@@ -1472,7 +1480,7 @@ void scoutfs_free_unused_locks(struct super_block *sb)
 		.nr_to_scan = INT_MAX,
 	};
 
-	linfo->shrinker.shrink(&linfo->shrinker, &sc);
+	lock_scan_objects(KC_SHRINKER_FN(&linfo->shrinker), &sc);
 }
 
 static void lock_tseq_show(struct seq_file *m, struct scoutfs_tseq_entry *ent)
@@ -1579,7 +1587,7 @@ void scoutfs_lock_shutdown(struct super_block *sb)
 	trace_scoutfs_lock_shutdown(sb, linfo);
 
 	/* stop the shrinker from queueing work */
-	unregister_shrinker(&linfo->shrinker);
+	KC_UNREGISTER_SHRINKER(&linfo->shrinker);
 	flush_work(&linfo->shrink_work);
 
 	/* cause current and future lock calls to return errors */
@@ -1698,9 +1706,9 @@ int scoutfs_lock_setup(struct super_block *sb)
 	spin_lock_init(&linfo->lock);
 	linfo->lock_tree = RB_ROOT;
 	linfo->lock_range_tree = RB_ROOT;
-	linfo->shrinker.shrink = scoutfs_lock_shrink;
-	linfo->shrinker.seeks = DEFAULT_SEEKS;
-	register_shrinker(&linfo->shrinker);
+	KC_INIT_SHRINKER_FUNCS(&linfo->shrinker, lock_count_objects,
+			       lock_scan_objects);
+	KC_REGISTER_SHRINKER(&linfo->shrinker);
 	INIT_LIST_HEAD(&linfo->lru_list);
 	INIT_WORK(&linfo->inv_work, lock_invalidate_worker);
 	INIT_LIST_HEAD(&linfo->inv_list);

kmod/src/util.h

@@ -17,4 +17,15 @@ static inline void down_write_two(struct rw_semaphore *a,
 	down_write_nested(b, SINGLE_DEPTH_NESTING);
 }
 
+/*
+ * When returning shrinker counts from scan_objects, we should steer
+ * clear of the magic SHRINK_STOP and SHRINK_EMPTY values, which are near
+ * ~0UL values. Hence, we cap count to ~0L, which is arbitarily high
+ * enough to avoid it.
+ */
+static inline long shrinker_min_long(long count)
+{
+	return min(count, LONG_MAX);
+}
+
 #endif