Remove duplicate code in l2arc_evict()

l2arc_evict() performs the adjustment of the size of buffers to be
written on L2ARC unnecessarily. l2arc_write_size() is called right
before l2arc_evict() and performs those adjustments.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Brian Atkinson <batkinson@lanl.gov>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
Closes #14828

module/zfs/arc.c

@@ -8198,10 +8198,17 @@ l2arc_write_size(l2arc_dev_t *dev)
 	 * iteration can occur.
 	 */
 	dev_size = dev->l2ad_end - dev->l2ad_start;
+
+	/* We need to add in the worst case scenario of log block overhead. */
 	tsize = size + l2arc_log_blk_overhead(size, dev);
-	if (dev->l2ad_vdev->vdev_has_trim && l2arc_trim_ahead > 0)
+	if (dev->l2ad_vdev->vdev_has_trim && l2arc_trim_ahead > 0) {
+		/*
+		 * Trim ahead of the write size 64MB or (l2arc_trim_ahead/100)
+		 * times the writesize, whichever is greater.
+		 */
 		tsize += MAX(64 * 1024 * 1024,
 		    (tsize * l2arc_trim_ahead) / 100);
+	}
 
 	if (tsize >= dev_size) {
 		cmn_err(CE_NOTE, "l2arc_write_max or l2arc_write_boost "
@@ -8836,19 +8843,6 @@ l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
 
 	buflist = &dev->l2ad_buflist;
 
-	/*
-	 * We need to add in the worst case scenario of log block overhead.
-	 */
-	distance += l2arc_log_blk_overhead(distance, dev);
-	if (vd->vdev_has_trim && l2arc_trim_ahead > 0) {
-		/*
-		 * Trim ahead of the write size 64MB or (l2arc_trim_ahead/100)
-		 * times the write size, whichever is greater.
-		 */
-		distance += MAX(64 * 1024 * 1024,
-		    (distance * l2arc_trim_ahead) / 100);
-	}
-
 top:
 	rerun = B_FALSE;
 	if (dev->l2ad_hand >= (dev->l2ad_end - distance)) {

tests/zfs-tests/tests/functional/trim/trim_l2arc.ksh

@@ -67,7 +67,7 @@ typeset VDEV_MIN_MB=$((MINVDEVSIZE * 0.30 / 1024 / 1024))
 log_must zpool create -f $TESTPOOL $TRIM_VDEV1 cache $TRIM_VDEV2
 verify_vdevs "-le" "$VDEV_MIN_MB" $TRIM_VDEV2
 
-typeset fill_mb=$(( floor(2 * MINVDEVSIZE) ))
+typeset fill_mb=$(( floor(3 * MINVDEVSIZE) ))
 export DIRECTORY=/$TESTPOOL
 export NUMJOBS=1
 export FILE_SIZE=${fill_mb}