Improve zfs_blkptr_verify()

- Skip config lock enter/exit for embedded blocks.  They have no
DVAs, so there is nothing to check under the lock.
 - Skip CHECKSUM check and properly check PSIZE for embedded blocks.
 - Add static branch predictions for unlikely conditions.
 - Do not verify DVAs for blocks already in ARC.  ARC hit already
"verified" the first (often the only) DVA, and it does not worth to
enter/exit config lock for nothing.

Some profiles show me up to 3% of CPU saving from this change.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Allan Jude <allan@klarasystems.com>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #16387

module/zfs/arc.c

@@ -5576,19 +5576,6 @@ arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
 	 */
 	fstrans_cookie_t cookie = spl_fstrans_mark();
 top:
-	/*
-	 * Verify the block pointer contents are reasonable.  This should
-	 * always be the case since the blkptr is protected by a checksum.
-	 * However, if there is damage it's desirable to detect this early
-	 * and treat it as a checksum error.  This allows an alternate blkptr
-	 * to be tried when one is available (e.g. ditto blocks).
-	 */
-	if (!zfs_blkptr_verify(spa, bp, (zio_flags & ZIO_FLAG_CONFIG_WRITER) ?
-	    BLK_CONFIG_HELD : BLK_CONFIG_NEEDED, BLK_VERIFY_LOG)) {
-		rc = SET_ERROR(ECKSUM);
-		goto done;
-	}
-
 	if (!embedded_bp) {
 		/*
 		 * Embedded BP's have no DVA and require no I/O to "read".
@@ -5608,6 +5595,18 @@ top:
 	    (hdr->b_l1hdr.b_pabd != NULL && !encrypted_read))) {
 		boolean_t is_data = !HDR_ISTYPE_METADATA(hdr);
 
+		/*
+		 * Verify the block pointer contents are reasonable.  This
+		 * should always be the case since the blkptr is protected by
+		 * a checksum.
+		 */
+		if (!zfs_blkptr_verify(spa, bp, BLK_CONFIG_SKIP,
+		    BLK_VERIFY_LOG)) {
+			mutex_exit(hash_lock);
+			rc = SET_ERROR(ECKSUM);
+			goto done;
+		}
+
 		if (HDR_IO_IN_PROGRESS(hdr)) {
 			if (*arc_flags & ARC_FLAG_CACHED_ONLY) {
 				mutex_exit(hash_lock);
@@ -5761,6 +5760,20 @@ top:
 			goto done;
 		}
 
+		/*
+		 * Verify the block pointer contents are reasonable.  This
+		 * should always be the case since the blkptr is protected by
+		 * a checksum.
+		 */
+		if (!zfs_blkptr_verify(spa, bp,
+		    (zio_flags & ZIO_FLAG_CONFIG_WRITER) ?
+		    BLK_CONFIG_HELD : BLK_CONFIG_NEEDED, BLK_VERIFY_LOG)) {
+			if (hash_lock != NULL)
+				mutex_exit(hash_lock);
+			rc = SET_ERROR(ECKSUM);
+			goto done;
+		}
+
 		if (hdr == NULL) {
 			/*
 			 * This block is not in the cache or it has

module/zfs/zio.c

@@ -1105,45 +1105,50 @@ zfs_blkptr_verify(spa_t *spa, const blkptr_t *bp,
 {
 	int errors = 0;
 
-	if (!DMU_OT_IS_VALID(BP_GET_TYPE(bp))) {
+	if (unlikely(!DMU_OT_IS_VALID(BP_GET_TYPE(bp)))) {
 		errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
 		    "blkptr at %px has invalid TYPE %llu",
 		    bp, (longlong_t)BP_GET_TYPE(bp));
 	}
-	if (BP_GET_CHECKSUM(bp) >= ZIO_CHECKSUM_FUNCTIONS) {
+	if (unlikely(BP_GET_COMPRESS(bp) >= ZIO_COMPRESS_FUNCTIONS)) {
-		errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
-		    "blkptr at %px has invalid CHECKSUM %llu",
-		    bp, (longlong_t)BP_GET_CHECKSUM(bp));
-	}
-	if (BP_GET_COMPRESS(bp) >= ZIO_COMPRESS_FUNCTIONS) {
 		errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
 		    "blkptr at %px has invalid COMPRESS %llu",
 		    bp, (longlong_t)BP_GET_COMPRESS(bp));
 	}
-	if (BP_GET_LSIZE(bp) > SPA_MAXBLOCKSIZE) {
+	if (unlikely(BP_GET_LSIZE(bp) > SPA_MAXBLOCKSIZE)) {
 		errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
 		    "blkptr at %px has invalid LSIZE %llu",
 		    bp, (longlong_t)BP_GET_LSIZE(bp));
 	}
-	if (BP_GET_PSIZE(bp) > SPA_MAXBLOCKSIZE) {
-		errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
-		    "blkptr at %px has invalid PSIZE %llu",
-		    bp, (longlong_t)BP_GET_PSIZE(bp));
-	}
-
 	if (BP_IS_EMBEDDED(bp)) {
-		if (BPE_GET_ETYPE(bp) >= NUM_BP_EMBEDDED_TYPES) {
+		if (unlikely(BPE_GET_ETYPE(bp) >= NUM_BP_EMBEDDED_TYPES)) {
 			errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
 			    "blkptr at %px has invalid ETYPE %llu",
 			    bp, (longlong_t)BPE_GET_ETYPE(bp));
 		}
+		if (unlikely(BPE_GET_PSIZE(bp) > BPE_PAYLOAD_SIZE)) {
+			errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
+			    "blkptr at %px has invalid PSIZE %llu",
+			    bp, (longlong_t)BPE_GET_PSIZE(bp));
+		}
+		return (errors == 0);
+	}
+	if (unlikely(BP_GET_CHECKSUM(bp) >= ZIO_CHECKSUM_FUNCTIONS)) {
+		errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
+		    "blkptr at %px has invalid CHECKSUM %llu",
+		    bp, (longlong_t)BP_GET_CHECKSUM(bp));
+	}
+	if (unlikely(BP_GET_PSIZE(bp) > SPA_MAXBLOCKSIZE)) {
+		errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
+		    "blkptr at %px has invalid PSIZE %llu",
+		    bp, (longlong_t)BP_GET_PSIZE(bp));
 	}
 
 	/*
 	 * Do not verify individual DVAs if the config is not trusted. This
 	 * will be done once the zio is executed in vdev_mirror_map_alloc.
 	 */
-	if (!spa->spa_trust_config)
+	if (unlikely(!spa->spa_trust_config))
 		return (errors == 0);
 
 	switch (blk_config) {
@@ -1172,20 +1177,20 @@ zfs_blkptr_verify(spa_t *spa, const blkptr_t *bp,
 		const dva_t *dva = &bp->blk_dva[i];
 		uint64_t vdevid = DVA_GET_VDEV(dva);
 
-		if (vdevid >= spa->spa_root_vdev->vdev_children) {
+		if (unlikely(vdevid >= spa->spa_root_vdev->vdev_children)) {
 			errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
 			    "blkptr at %px DVA %u has invalid VDEV %llu",
 			    bp, i, (longlong_t)vdevid);
 			continue;
 		}
 		vdev_t *vd = spa->spa_root_vdev->vdev_child[vdevid];
-		if (vd == NULL) {
+		if (unlikely(vd == NULL)) {
 			errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
 			    "blkptr at %px DVA %u has invalid VDEV %llu",
 			    bp, i, (longlong_t)vdevid);
 			continue;
 		}
-		if (vd->vdev_ops == &vdev_hole_ops) {
+		if (unlikely(vd->vdev_ops == &vdev_hole_ops)) {
 			errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
 			    "blkptr at %px DVA %u has hole VDEV %llu",
 			    bp, i, (longlong_t)vdevid);
@@ -1203,7 +1208,7 @@ zfs_blkptr_verify(spa_t *spa, const blkptr_t *bp,
 		uint64_t asize = DVA_GET_ASIZE(dva);
 		if (DVA_GET_GANG(dva))
 			asize = vdev_gang_header_asize(vd);
-		if (offset + asize > vd->vdev_asize) {
+		if (unlikely(offset + asize > vd->vdev_asize)) {
 			errors += zfs_blkptr_verify_log(spa, bp, blk_verify,
 			    "blkptr at %px DVA %u has invalid OFFSET %llu",
 			    bp, i, (longlong_t)offset);