Add TRIM support for L2ARC.

This adds TRIM support to cache vdevs. When ARC buffers are removed
from the L2ARC in arc_hdr_destroy(), arc_release() or l2arc_evict(),
the size previously occupied by the buffer gets scheduled for TRIMming.
As always, actual TRIMs are only issued to the L2ARC after
txg_trim_limit.

include/sys/trim_map.h

@@ -36,7 +36,7 @@ extern "C" {
 
 extern void trim_map_create(vdev_t *vd);
 extern void trim_map_destroy(vdev_t *vd);
-extern void trim_map_free(zio_t *zio);
+extern void trim_map_free(vdev_t *vd, uint64_t offset, uint64_t size);
 extern boolean_t trim_map_write_start(zio_t *zio);
 extern void trim_map_write_done(zio_t *zio);
 

module/zfs/arc.c

@@ -141,6 +141,7 @@
 #include <sys/callb.h>
 #include <sys/kstat.h>
 #include <sys/dmu_tx.h>
+#include <sys/trim_map.h>
 #include <zfs_fletcher.h>
 
 static kmutex_t		arc_reclaim_thr_lock;
@@ -1519,6 +1520,8 @@ arc_hdr_destroy(arc_buf_hdr_t *hdr)
 		}
 
 		if (l2hdr != NULL) {
+			trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr,
+			     hdr->b_size);
 			list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
 			ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
 			kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
@@ -3376,6 +3379,8 @@ arc_release(arc_buf_t *buf, void *tag)
 	buf->b_private = NULL;
 
 	if (l2hdr) {
+		trim_map_free(l2hdr->b_dev->l2ad_vdev, l2hdr->b_daddr,
+		     hdr->b_size);
 		list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
 		kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
 		ARCSTAT_INCR(arcstat_l2_size, -buf_size);
@@ -4487,6 +4492,8 @@ l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
 			if (ab->b_l2hdr != NULL) {
 				abl2 = ab->b_l2hdr;
 				ab->b_l2hdr = NULL;
+				trim_map_free(abl2->b_dev->l2ad_vdev, abl2->b_daddr,
+				     ab->b_size);
 				kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
 				ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
 			}

module/zfs/trim_map.c

@@ -192,7 +192,7 @@ trim_map_segment_add(trim_map_t *tm, uint64_t start, uint64_t end, uint64_t txg)
 	} else if (merge_after) {
 		ts_after->ts_start = start;
 	} else {
-		ts = kmem_alloc(sizeof (*ts), KM_SLEEP);
+		ts = kmem_alloc(sizeof (*ts), KM_PUSHPAGE);
 		ts->ts_start = start;
 		ts->ts_end = end;
 		ts->ts_txg = txg;
@@ -261,16 +261,15 @@ trim_map_free_locked(trim_map_t *tm, uint64_t start, uint64_t end, uint64_t txg)
 }
 
 void
-trim_map_free(zio_t *zio)
+trim_map_free(vdev_t *vd, uint64_t offset, uint64_t size)
 {
-	vdev_t *vd = zio->io_vd;
 	trim_map_t *tm = vd->vdev_trimmap;
 
 	if (zfs_notrim || vd->vdev_notrim || tm == NULL)
 		return;
 
 	mutex_enter(&tm->tm_lock);
-	trim_map_free_locked(tm, zio->io_offset, zio->io_offset + zio->io_size,
+	trim_map_free_locked(tm, offset, offset + size,
 	    vd->vdev_spa->spa_syncing_txg);
 	mutex_exit(&tm->tm_lock);
 }

module/zfs/zio.c

@@ -2454,7 +2454,7 @@ zio_vdev_io_start(zio_t *zio)
 	}
 
 	if (vd->vdev_ops->vdev_op_leaf && zio->io_type == ZIO_TYPE_FREE) {
-		trim_map_free(zio);
+		trim_map_free(vd, zio->io_offset, zio->io_size);
 		return (ZIO_PIPELINE_CONTINUE);
 	}