Unify arc_prune_async() code

There is no sense to have separate implementations for FreeBSD and
Linux.  Make Linux code shared as more functional and just register
FreeBSD-specific prune callback with arc_add_prune_callback() API.

Aside of code cleanup this should fix excessive pruning on FreeBSD:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=274698

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Mark Johnston <markj@FreeBSD.org>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #15456

include/os/linux/zfs/sys/zpl.h

@@ -60,7 +60,7 @@ extern const struct file_operations zpl_file_operations;
 extern const struct file_operations zpl_dir_file_operations;
 
 /* zpl_super.c */
-extern void zpl_prune_sb(int64_t nr_to_scan, void *arg);
+extern void zpl_prune_sb(uint64_t nr_to_scan, void *arg);
 
 extern const struct super_operations zpl_super_operations;
 extern const struct export_operations zpl_export_operations;

include/sys/arc.h

@@ -81,7 +81,7 @@ typedef struct arc_prune arc_prune_t;
 typedef void arc_read_done_func_t(zio_t *zio, const zbookmark_phys_t *zb,
     const blkptr_t *bp, arc_buf_t *buf, void *priv);
 typedef void arc_write_done_func_t(zio_t *zio, arc_buf_t *buf, void *priv);
-typedef void arc_prune_func_t(int64_t bytes, void *priv);
+typedef void arc_prune_func_t(uint64_t bytes, void *priv);
 
 /* Shared module parameters */
 extern uint_t zfs_arc_average_blocksize;

include/sys/arc_impl.h

@@ -1065,7 +1065,6 @@ extern void arc_wait_for_eviction(uint64_t, boolean_t);
 
 extern void arc_lowmem_init(void);
 extern void arc_lowmem_fini(void);
-extern void arc_prune_async(uint64_t);
 extern int arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg);
 extern uint64_t arc_free_memory(void);
 extern int64_t arc_available_memory(void);

module/os/freebsd/zfs/arc_os.c

@@ -52,11 +52,6 @@
 #include <sys/vm.h>
 #include <sys/vmmeter.h>
 
-#if __FreeBSD_version >= 1300139
-static struct sx arc_vnlru_lock;
-static struct vnode *arc_vnlru_marker;
-#endif
-
 extern struct vfsops zfs_vfsops;
 
 uint_t zfs_arc_free_target = 0;
@@ -131,53 +126,6 @@ arc_default_max(uint64_t min, uint64_t allmem)
 	return (MAX(allmem * 5 / 8, size));
 }
 
-/*
- * Helper function for arc_prune_async() it is responsible for safely
- * handling the execution of a registered arc_prune_func_t.
- */
-static void
-arc_prune_task(void *arg)
-{
-	uint64_t nr_scan = (uintptr_t)arg;
-
-#ifndef __ILP32__
-	if (nr_scan > INT_MAX)
-		nr_scan = INT_MAX;
-#endif
-
-#if __FreeBSD_version >= 1300139
-	sx_xlock(&arc_vnlru_lock);
-	vnlru_free_vfsops(nr_scan, &zfs_vfsops, arc_vnlru_marker);
-	sx_xunlock(&arc_vnlru_lock);
-#else
-	vnlru_free(nr_scan, &zfs_vfsops);
-#endif
-}
-
-/*
- * Notify registered consumers they must drop holds on a portion of the ARC
- * buffered they reference.  This provides a mechanism to ensure the ARC can
- * honor the metadata limit and reclaim otherwise pinned ARC buffers.  This
- * is analogous to dnlc_reduce_cache() but more generic.
- *
- * This operation is performed asynchronously so it may be safely called
- * in the context of the arc_reclaim_thread().  A reference is taken here
- * for each registered arc_prune_t and the arc_prune_task() is responsible
- * for releasing it once the registered arc_prune_func_t has completed.
- */
-void
-arc_prune_async(uint64_t adjust)
-{
-
-#ifndef __LP64__
-	if (adjust > UINTPTR_MAX)
-		adjust = UINTPTR_MAX;
-#endif
-	taskq_dispatch(arc_prune_taskq, arc_prune_task,
-	    (void *)(intptr_t)adjust, TQ_SLEEP);
-	ARCSTAT_BUMP(arcstat_prune);
-}
-
 uint64_t
 arc_all_memory(void)
 {
@@ -228,10 +176,6 @@ arc_lowmem_init(void)
 {
 	arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
 	    EVENTHANDLER_PRI_FIRST);
-#if __FreeBSD_version >= 1300139
-	arc_vnlru_marker = vnlru_alloc_marker();
-	sx_init(&arc_vnlru_lock, "arc vnlru lock");
-#endif
 }
 
 void
@@ -239,12 +183,6 @@ arc_lowmem_fini(void)
 {
 	if (arc_event_lowmem != NULL)
 		EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
-#if __FreeBSD_version >= 1300139
-	if (arc_vnlru_marker != NULL) {
-		vnlru_free_marker(arc_vnlru_marker);
-		sx_destroy(&arc_vnlru_lock);
-	}
-#endif
 }
 
 void

module/os/freebsd/zfs/zfs_vfsops.c

@@ -2070,6 +2070,26 @@ zfs_vnodes_adjust_back(void)
 #endif
 }
 
+#if __FreeBSD_version >= 1300139
+static struct sx zfs_vnlru_lock;
+static struct vnode *zfs_vnlru_marker;
+#endif
+static arc_prune_t *zfs_prune;
+
+static void
+zfs_prune_task(uint64_t nr_to_scan, void *arg __unused)
+{
+	if (nr_to_scan > INT_MAX)
+		nr_to_scan = INT_MAX;
+#if __FreeBSD_version >= 1300139
+	sx_xlock(&zfs_vnlru_lock);
+	vnlru_free_vfsops(nr_to_scan, &zfs_vfsops, zfs_vnlru_marker);
+	sx_xunlock(&zfs_vnlru_lock);
+#else
+	vnlru_free(nr_to_scan, &zfs_vfsops);
+#endif
+}
+
 void
 zfs_init(void)
 {
@@ -2096,11 +2116,23 @@ zfs_init(void)
 	dmu_objset_register_type(DMU_OST_ZFS, zpl_get_file_info);
 
 	zfsvfs_taskq = taskq_create("zfsvfs", 1, minclsyspri, 0, 0, 0);
+
+#if __FreeBSD_version >= 1300139
+	zfs_vnlru_marker = vnlru_alloc_marker();
+	sx_init(&zfs_vnlru_lock, "zfs vnlru lock");
+#endif
+	zfs_prune = arc_add_prune_callback(zfs_prune_task, NULL);
 }
 
 void
 zfs_fini(void)
 {
+	arc_remove_prune_callback(zfs_prune);
+#if __FreeBSD_version >= 1300139
+	vnlru_free_marker(zfs_vnlru_marker);
+	sx_destroy(&zfs_vnlru_lock);
+#endif
+
 	taskq_destroy(zfsvfs_taskq);
 	zfsctl_fini();
 	zfs_znode_fini();

module/os/linux/zfs/arc_os.c

@@ -489,56 +489,5 @@ arc_unregister_hotplug(void)
 }
 #endif /* _KERNEL */
 
-/*
- * Helper function for arc_prune_async() it is responsible for safely
- * handling the execution of a registered arc_prune_func_t.
- */
-static void
-arc_prune_task(void *ptr)
-{
-	arc_prune_t *ap = (arc_prune_t *)ptr;
-	arc_prune_func_t *func = ap->p_pfunc;
-
-	if (func != NULL)
-		func(ap->p_adjust, ap->p_private);
-
-	zfs_refcount_remove(&ap->p_refcnt, func);
-}
-
-/*
- * Notify registered consumers they must drop holds on a portion of the ARC
- * buffered they reference.  This provides a mechanism to ensure the ARC can
- * honor the metadata limit and reclaim otherwise pinned ARC buffers.  This
- * is analogous to dnlc_reduce_cache() but more generic.
- *
- * This operation is performed asynchronously so it may be safely called
- * in the context of the arc_reclaim_thread().  A reference is taken here
- * for each registered arc_prune_t and the arc_prune_task() is responsible
- * for releasing it once the registered arc_prune_func_t has completed.
- */
-void
-arc_prune_async(uint64_t adjust)
-{
-	arc_prune_t *ap;
-
-	mutex_enter(&arc_prune_mtx);
-	for (ap = list_head(&arc_prune_list); ap != NULL;
-	    ap = list_next(&arc_prune_list, ap)) {
-
-		if (zfs_refcount_count(&ap->p_refcnt) >= 2)
-			continue;
-
-		zfs_refcount_add(&ap->p_refcnt, ap->p_pfunc);
-		ap->p_adjust = adjust;
-		if (taskq_dispatch(arc_prune_taskq, arc_prune_task,
-		    ap, TQ_SLEEP) == TASKQID_INVALID) {
-			zfs_refcount_remove(&ap->p_refcnt, ap->p_pfunc);
-			continue;
-		}
-		ARCSTAT_BUMP(arcstat_prune);
-	}
-	mutex_exit(&arc_prune_mtx);
-}
-
 ZFS_MODULE_PARAM(zfs_arc, zfs_arc_, shrinker_limit, INT, ZMOD_RW,
 	"Limit on number of pages that ARC shrinker can reclaim at once");

module/os/linux/zfs/zpl_super.c

@@ -375,7 +375,7 @@ zpl_kill_sb(struct super_block *sb)
 }
 
 void
-zpl_prune_sb(int64_t nr_to_scan, void *arg)
+zpl_prune_sb(uint64_t nr_to_scan, void *arg)
 {
 	struct super_block *sb = (struct super_block *)arg;
 	int objects = 0;

module/zfs/arc.c

@@ -886,6 +886,8 @@ static void l2arc_do_free_on_write(void);
 static void l2arc_hdr_arcstats_update(arc_buf_hdr_t *hdr, boolean_t incr,
     boolean_t state_only);
 
+static void arc_prune_async(uint64_t adjust);
+
 #define	l2arc_hdr_arcstats_increment(hdr) \
 	l2arc_hdr_arcstats_update((hdr), B_TRUE, B_FALSE)
 #define	l2arc_hdr_arcstats_decrement(hdr) \
@@ -6050,6 +6052,56 @@ arc_remove_prune_callback(arc_prune_t *p)
 	kmem_free(p, sizeof (*p));
 }
 
+/*
+ * Helper function for arc_prune_async() it is responsible for safely
+ * handling the execution of a registered arc_prune_func_t.
+ */
+static void
+arc_prune_task(void *ptr)
+{
+	arc_prune_t *ap = (arc_prune_t *)ptr;
+	arc_prune_func_t *func = ap->p_pfunc;
+
+	if (func != NULL)
+		func(ap->p_adjust, ap->p_private);
+
+	zfs_refcount_remove(&ap->p_refcnt, func);
+}
+
+/*
+ * Notify registered consumers they must drop holds on a portion of the ARC
+ * buffers they reference.  This provides a mechanism to ensure the ARC can
+ * honor the metadata limit and reclaim otherwise pinned ARC buffers.
+ *
+ * This operation is performed asynchronously so it may be safely called
+ * in the context of the arc_reclaim_thread().  A reference is taken here
+ * for each registered arc_prune_t and the arc_prune_task() is responsible
+ * for releasing it once the registered arc_prune_func_t has completed.
+ */
+static void
+arc_prune_async(uint64_t adjust)
+{
+	arc_prune_t *ap;
+
+	mutex_enter(&arc_prune_mtx);
+	for (ap = list_head(&arc_prune_list); ap != NULL;
+	    ap = list_next(&arc_prune_list, ap)) {
+
+		if (zfs_refcount_count(&ap->p_refcnt) >= 2)
+			continue;
+
+		zfs_refcount_add(&ap->p_refcnt, ap->p_pfunc);
+		ap->p_adjust = adjust;
+		if (taskq_dispatch(arc_prune_taskq, arc_prune_task,
+		    ap, TQ_SLEEP) == TASKQID_INVALID) {
+			zfs_refcount_remove(&ap->p_refcnt, ap->p_pfunc);
+			continue;
+		}
+		ARCSTAT_BUMP(arcstat_prune);
+	}
+	mutex_exit(&arc_prune_mtx);
+}
+
 /*
  * Notify the arc that a block was freed, and thus will never be used again.
  */