l2arc: do not call trim_map_free() for blocks with zero b_asize

b_asize can be zero if the block is compressed into an empty block
(ZIO_COMPRESS_EMPTY) and the trim code asserts that meaningless
zero-sized trimming is not attempted.
The logic for calling trim_map_free() is extracted into a new function
l2arc_trim() to minimize code duplication.

PR:		203473
Reported by:	Willem Jan Withagen <wjw@digiware.nl>
Tested by:	Willem Jan Withagen <wjw@digiware.nl>
MFC after:	11 days

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
index ba16dedcecdc0d0c2147047cc92bd69252381cd8..0123a799eea5061a30dbc113863c7bfcfe78ae4a 100644 (file)
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
@@ -1131,6 +1131,24 @@ static boolean_t l2arc_compress_buf(arc_buf_hdr_t *);
 static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress);
 static void l2arc_release_cdata_buf(arc_buf_hdr_t *);
 
+static void
+l2arc_trim(const arc_buf_hdr_t *hdr)
+{
+       l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
+
+       ASSERT(HDR_HAS_L2HDR(hdr));
+       ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
+
+       if (hdr->b_l2hdr.b_daddr == L2ARC_ADDR_UNSET)
+               return;
+       if (hdr->b_l2hdr.b_asize != 0) {
+               trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr,
+                   hdr->b_l2hdr.b_asize, 0);
+       } else {
+               ASSERT3U(hdr->b_l2hdr.b_compress, ==, ZIO_COMPRESS_EMPTY);
+       }
+}
+
 static uint64_t
 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
 {
@@ -2403,10 +2421,7 @@ arc_hdr_destroy(arc_buf_hdr_t *hdr)
                 * want to re-destroy the header's L2 portion.
                 */
                if (HDR_HAS_L2HDR(hdr)) {
-                       if (hdr->b_l2hdr.b_daddr != L2ARC_ADDR_UNSET)
-                               trim_map_free(dev->l2ad_vdev,
-                                   hdr->b_l2hdr.b_daddr,
-                                   hdr->b_l2hdr.b_asize, 0);
+                       l2arc_trim(hdr);
                        arc_hdr_l2hdr_destroy(hdr);
                }
 
@@ -4776,10 +4791,7 @@ arc_release(arc_buf_t *buf, void *tag)
                 * to acquire the l2ad_mtx.
                 */
                if (HDR_HAS_L2HDR(hdr)) {
-                       if (hdr->b_l2hdr.b_daddr != L2ARC_ADDR_UNSET)
-                               trim_map_free(hdr->b_l2hdr.b_dev->l2ad_vdev,
-                                   hdr->b_l2hdr.b_daddr,
-                                   hdr->b_l2hdr.b_asize, 0);
+                       l2arc_trim(hdr);
                        arc_hdr_l2hdr_destroy(hdr);
                }
 
@@ -5966,8 +5978,7 @@ top:
                         * Error - drop L2ARC entry.
                         */
                        list_remove(buflist, hdr);
-                       trim_map_free(hdr->b_l2hdr.b_dev->l2ad_vdev,
-                           hdr->b_l2hdr.b_daddr, hdr->b_l2hdr.b_asize, 0);
+                       l2arc_trim(hdr);
                        hdr->b_flags &= ~ARC_FLAG_HAS_L2HDR;
 
                        ARCSTAT_INCR(arcstat_l2_asize, -hdr->b_l2hdr.b_asize);