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>

kmod/src/Makefile

@@ -46,6 +46,10 @@ scoutfs-y +=			\
 	volopt.o		\
 	xattr.o
 
+ifdef KC_BUILD_KERNELCOMPAT
+scoutfs-y += kernelcompat.o
+endif
+
 #
 # The raw types aren't available in userspace headers.  Make sure all
 # the types we use in the headers are the exported __ versions.

kmod/src/Makefile.kernelcompat

@@ -73,3 +73,13 @@ 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
+KC_BUILD_KERNELCOMPAT=1
+endif

kmod/src/block.c

@@ -58,7 +58,7 @@ 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;
 };
@@ -1040,6 +1040,17 @@ 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 = container_of(shrink, struct block_info, shrinker);
+	struct super_block *sb = binf->sb;
+
+	scoutfs_inc_counter(sb, block_cache_scan_objects);
+
+	return min_t(u64, (u64)atomic_read(&binf->total_inserted) * SCOUTFS_BLOCK_LG_PAGES_PER,
+		     ULONG_MAX / 2); /* magic numbers as we approach ~0UL :/ */
+}
+
 /*
  * Remove a number of cached blocks that haven't been used recently.
  *
@@ -1060,23 +1071,19 @@ 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 = container_of(shrink, struct block_info, shrinker);
 	struct super_block *sb = binf->sb;
 	struct rhashtable_iter iter;
 	struct block_private *bp;
+	unsigned long freed = 0;
 	unsigned long nr;
 	u64 recently;
 
-	nr = sc->nr_to_scan;
-	if (nr == 0)
-		goto out;
+	scoutfs_inc_counter(sb, block_cache_scan_objects);
 
-	scoutfs_inc_counter(sb, block_cache_shrink);
-
-	nr = DIV_ROUND_UP(nr, SCOUTFS_BLOCK_LG_PAGES_PER);
+	nr = DIV_ROUND_UP(sc->nr_to_scan, SCOUTFS_BLOCK_LG_PAGES_PER);
 
 restart:
 	recently = accessed_recently(binf);
@@ -1119,6 +1126,7 @@ restart:
 			if (block_remove_solo(sb, bp)) {
 				scoutfs_inc_counter(sb, block_cache_shrink_remove);
 				TRACE_BLOCK(shrink, bp);
+				freed++;
 				nr--;
 			}
 			block_put(sb, bp);
@@ -1127,9 +1135,8 @@ restart:
 
 	rhashtable_walk_stop(&iter);
 	rhashtable_walk_exit(&iter);
-out:
-	return min_t(u64, (u64)atomic_read(&binf->total_inserted) * SCOUTFS_BLOCK_LG_PAGES_PER,
-		     INT_MAX);
+
+	return freed;
 }
 
 struct sm_block_completion {
@@ -1255,7 +1262,8 @@ 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;
+	KC_INIT_SHRINKER_FUNCS(struct block_info, shrinker,
+			       &binf->shrinker, block_count_objects, block_scan_objects);
 	binf->shrinker.seeks = DEFAULT_SEEKS;
 	register_shrinker(&binf->shrinker);
 	INIT_WORK(&binf->free_work, block_free_work);

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)		\

kmod/src/kernelcompat.c

@@ -0,0 +1,23 @@
+
+#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(struct shrinker *shrink, struct shrink_control *sc)
+{
+	struct kc_shrinker_funcs *funcs = KC_SHRINKER_FUNCS(shrink);
+	unsigned long nr;
+
+	if (sc->nr_to_scan != 0)
+		funcs->scan_objects(shrink, sc);
+
+	nr = funcs->count_objects(shrink, sc);
+
+	return min_t(unsigned long, nr, INT_MAX);
+}
+#endif

kmod/src/kernelcompat.h

@@ -91,4 +91,36 @@ 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(type, name, shrink, count, scan) do {	\
+	__typeof__(shrink) _shrink = (shrink);				\
+	_shrink->count_objects = count;					\
+	_shrink->scan_objects = scan;					\
+} while (0)
+#else
+#include <linux/shrinker.h>
+struct kc_shrinker_funcs {
+	unsigned long (*count_objects)(struct shrinker *, struct shrink_control *sc);
+	unsigned long (*scan_objects)(struct shrinker *, struct shrink_control *sc);
+};
+/* using adjacent member of an unnamed struct */
+#define KC_DEFINE_SHRINKER(name)				\
+	{							\
+		struct kc_shrinker_funcs shrinker_funcs;	\
+		struct shinker name;				\
+	}
+#define KC_SHRINKER_FUNCS(shrinker) \
+	((void *)((long)(shrink) - sizeof(struct kc_shrinker_funcs)))
+#define KC_INIT_SHRINKER_FUNCS(type, name, shrink, count, scan) do {				\
+	BUILD_BUG_ON(offsetof(cont, shrink_funcs) + sizeof(struct kc_shrinker_funcs)) !=	\
+		     offsetof(cont, name) + sizeof(struct kc_shrinker_funcs);			\
+	struct kc_shrinker_funcs *_funcs = KC_SHRINKER_FUNCS(shrink)				\
+	__typeof__(shrink) _shrink = (shrink);							\
+	_funcs->count_objects = count;								\
+	_funcs->scan_objects = scan;								\
+	_shrink->shrink = kc_shrink_wrapper;							\
+} while (0)
+#endif
+
 #endif