Illumos 5027 - zfs large block support

5027 zfs large block support
Reviewed by: Alek Pinchuk <[email protected]>
Reviewed by: George Wilson <[email protected]>
Reviewed by: Josef 'Jeff' Sipek <[email protected]>
Reviewed by: Richard Elling <[email protected]>
Reviewed by: Saso Kiselkov <[email protected]>
Reviewed by: Brian Behlendorf <[email protected]>
Approved by: Dan McDonald <[email protected]>

References:
  https://www.illumos.org/issues/5027
  https://github.com/illumos/illumos-gate/commit/b515258

Porting Notes:

* Included in this patch is a tiny ISP2() cleanup in zio_init() from
Illumos 5255.

* Unlike the upstream Illumos commit this patch does not impose an
arbitrary 128K block size limit on volumes.  Volumes, like filesystems,
are limited by the zfs_max_recordsize=1M module option.

* By default the maximum record size is limited to 1M by the module
option zfs_max_recordsize.  This value may be safely increased up to
16M which is the largest block size supported by the on-disk format.
At the moment, 1M blocks clearly offer a significant performance
improvement but the benefits of going beyond this for the majority
of workloads are less clear.

* The illumos version of this patch increased DMU_MAX_ACCESS to 32M.
This was determined not to be large enough when using 16M blocks
because the zfs_make_xattrdir() function will fail (EFBIG) when
assigning a TX.  This was immediately observed under Linux because
all newly created files must have a security xattr created and
that was failing.  Therefore, we've set DMU_MAX_ACCESS to 64M.

* On 32-bit platforms a hard limit of 1M is set for blocks due
to the limited virtual address space.  We should be able to relax
this one the ABD patches are merged.

Ported-by: Brian Behlendorf <[email protected]>
Closes #354

55 files changed, 613 insertions, 155 deletions

diff --git a/cmd/zdb/zdb.c b/cmd/zdb/zdb.c
index 25f44212a..ab6155054 100644
--- a/cmd/zdb/zdb.c
+++ b/cmd/zdb/zdb.c
@@ -2185,6 +2185,8 @@ dump_label(const char *dev)
 	(void) close(fd);
 }
 
+static uint64_t num_large_blocks;
+
 /*ARGSUSED*/
 static int
 dump_one_dir(const char *dsname, void *arg)
@@ -2197,6 +2199,8 @@ dump_one_dir(const char *dsname, void *arg)
 		(void) printf("Could not open %s, error %d\n", dsname, error);
 		return (0);
 	}
+	if (dmu_objset_ds(os)->ds_large_blocks)
+		num_large_blocks++;
 	dump_dir(os);
 	dmu_objset_disown(os, FTAG);
 	fuid_table_destroy();
@@ -2207,7 +2211,7 @@ dump_one_dir(const char *dsname, void *arg)
 /*
  * Block statistics.
  */
-#define	PSIZE_HISTO_SIZE (SPA_MAXBLOCKSIZE / SPA_MINBLOCKSIZE + 1)
+#define	PSIZE_HISTO_SIZE (SPA_OLD_MAXBLOCKSIZE / SPA_MINBLOCKSIZE + 2)
 typedef struct zdb_blkstats {
 	uint64_t zb_asize;
 	uint64_t zb_lsize;
@@ -2273,7 +2277,15 @@ zdb_count_block(zdb_cb_t *zcb, zilog_t *zilog, const blkptr_t *bp,
 		zb->zb_lsize += BP_GET_LSIZE(bp);
 		zb->zb_psize += BP_GET_PSIZE(bp);
 		zb->zb_count++;
-		zb->zb_psize_histogram[BP_GET_PSIZE(bp) >> SPA_MINBLOCKSHIFT]++;
+
+		/*
+		 * The histogram is only big enough to record blocks up to
+		 * SPA_OLD_MAXBLOCKSIZE; larger blocks go into the last,
+		 * "other", bucket.
+		 */
+		int idx = BP_GET_PSIZE(bp) >> SPA_MINBLOCKSHIFT;
+		idx = MIN(idx, SPA_OLD_MAXBLOCKSIZE / SPA_MINBLOCKSIZE + 1);
+		zb->zb_psize_histogram[idx]++;
 
 		zb->zb_gangs += BP_COUNT_GANG(bp);
 
@@ -2979,6 +2991,7 @@ dump_zpool(spa_t *spa)
 		dump_metaslab_groups(spa);
 
 	if (dump_opt['d'] || dump_opt['i']) {
+		uint64_t refcount;
 		dump_dir(dp->dp_meta_objset);
 		if (dump_opt['d'] >= 3) {
 			dump_bpobj(&spa->spa_deferred_bpobj,
@@ -2998,8 +3011,21 @@ dump_zpool(spa_t *spa)
 		}
 		(void) dmu_objset_find(spa_name(spa), dump_one_dir,
 		    NULL, DS_FIND_SNAPSHOTS | DS_FIND_CHILDREN);
+
+		(void) feature_get_refcount(spa,
+		    &spa_feature_table[SPA_FEATURE_LARGE_BLOCKS], &refcount);
+		if (num_large_blocks != refcount) {
+			(void) printf("large_blocks feature refcount mismatch: "
+			    "expected %lld != actual %lld\n",
+			    (longlong_t)num_large_blocks,
+			    (longlong_t)refcount);
+			rc = 2;
+		} else {
+			(void) printf("Verified large_blocks feature refcount "
+			    "is correct (%llu)\n", (longlong_t)refcount);
+		}
 	}
-	if (dump_opt['b'] || dump_opt['c'])
+	if (rc == 0 && (dump_opt['b'] || dump_opt['c']))
 		rc = dump_block_stats(spa);
 
 	if (rc == 0)
diff --git a/cmd/zfs/zfs_main.c b/cmd/zfs/zfs_main.c
index 50ac59fba..32b9239b7 100644
--- a/cmd/zfs/zfs_main.c
+++ b/cmd/zfs/zfs_main.c
@@ -258,9 +258,9 @@ get_usage(zfs_help_t idx)
 	case HELP_ROLLBACK:
 		return (gettext("\trollback [-rRf] <snapshot>\n"));
 	case HELP_SEND:
-		return (gettext("\tsend [-DnPpRrve] [-[iI] snapshot] "
+		return (gettext("\tsend [-DnPpRvLe] [-[iI] snapshot] "
 		    "<snapshot>\n"
-		    "\tsend [-e] [-i snapshot|bookmark] "
+		    "\tsend [-Le] [-i snapshot|bookmark] "
 		    "<filesystem|volume|snapshot>\n"));
 	case HELP_SET:
 		return (gettext("\tset <property=value> "
@@ -3683,7 +3683,7 @@ zfs_do_send(int argc, char **argv)
 	boolean_t extraverbose = B_FALSE;
 
 	/* check options */
-	while ((c = getopt(argc, argv, ":i:I:RDpvnPe")) != -1) {
+	while ((c = getopt(argc, argv, ":i:I:RDpvnPLe")) != -1) {
 		switch (c) {
 		case 'i':
 			if (fromname)
@@ -3718,6 +3718,9 @@ zfs_do_send(int argc, char **argv)
 		case 'n':
 			flags.dryrun = B_TRUE;
 			break;
+		case 'L':
+			flags.largeblock = B_TRUE;
+			break;
 		case 'e':
 			flags.embed_data = B_TRUE;
 			break;
@@ -3774,6 +3777,8 @@ zfs_do_send(int argc, char **argv)
 		if (zhp == NULL)
 			return (1);
 
+		if (flags.largeblock)
+			lzc_flags |= LZC_SEND_FLAG_LARGE_BLOCK;
 		if (flags.embed_data)
 			lzc_flags |= LZC_SEND_FLAG_EMBED_DATA;
 
diff --git a/cmd/zstreamdump/zstreamdump.c b/cmd/zstreamdump/zstreamdump.c
index c51a9c806..176dd66b2 100644
--- a/cmd/zstreamdump/zstreamdump.c
+++ b/cmd/zstreamdump/zstreamdump.c
@@ -56,7 +56,6 @@ uint64_t total_stream_len = 0;
 FILE *send_stream = 0;
 boolean_t do_byteswap = B_FALSE;
 boolean_t do_cksum = B_TRUE;
-#define	INITIAL_BUFLEN (1<<20)
 
 static void
 usage(void)
@@ -69,6 +68,18 @@ usage(void)
 	exit(1);
 }
 
+static void *
+safe_malloc(size_t size)
+{
+	void *rv = malloc(size);
+	if (rv == NULL) {
+		(void) fprintf(stderr, "ERROR; failed to allocate %u bytes\n",
+		    (unsigned)size);
+		abort();
+	}
+	return (rv);
+}
+
 /*
  * ssread - send stream read.
  *
@@ -160,7 +171,7 @@ print_block(char *buf, int length)
 int
 main(int argc, char *argv[])
 {
-	char *buf = malloc(INITIAL_BUFLEN);
+	char *buf = safe_malloc(SPA_MAXBLOCKSIZE);
 	uint64_t drr_record_count[DRR_NUMTYPES] = { 0 };
 	uint64_t total_records = 0;
 	dmu_replay_record_t thedrr;
@@ -308,9 +319,9 @@ main(int argc, char *argv[])
 				nvlist_t *nv;
 				int sz = drr->drr_payloadlen;
 
-				if (sz > INITIAL_BUFLEN) {
+				if (sz > SPA_MAXBLOCKSIZE) {
 					free(buf);
-					buf = malloc(sz);
+					buf = safe_malloc(sz);
 				}
 				(void) ssread(buf, sz, &zc);
 				if (ferror(send_stream))
diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index 0602a7ec5..6b939bdb6 100644
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -1040,9 +1040,14 @@ ztest_spa_get_ashift(void) {
 static int
 ztest_random_blocksize(void)
 {
-	// Choose a block size >= the ashift.
-	uint64_t block_shift =
-	    ztest_random(SPA_MAXBLOCKSHIFT - ztest_spa_get_ashift() + 1);
+	/*
+	 * Choose a block size >= the ashift.
+	 * If the SPA supports new MAXBLOCKSIZE, test up to 1MB blocks.
+	 */
+	int maxbs = SPA_OLD_MAXBLOCKSHIFT;
+	if (spa_maxblocksize(ztest_spa) == SPA_MAXBLOCKSIZE)
+		maxbs = 20;
+	uint64_t block_shift = ztest_random(maxbs - ztest_spa_get_ashift() + 1);
 	return (1 << (SPA_MINBLOCKSHIFT + block_shift));
 }
 
@@ -4972,7 +4977,7 @@ ztest_fault_inject(ztest_ds_t *zd, uint64_t id)
 	char *path0;
 	char *pathrand;
 	size_t fsize;
-	int bshift = SPA_MAXBLOCKSHIFT + 2;	/* don't scrog all labels */
+	int bshift = SPA_OLD_MAXBLOCKSHIFT + 2;	/* don't scrog all labels */
 	int iters = 1000;
 	int maxfaults;
 	int mirror_save;
diff --git a/include/libzfs.h b/include/libzfs.h
index e6a877214..c4e30c5d4 100644
--- a/include/libzfs.h
+++ b/include/libzfs.h
@@ -617,6 +617,9 @@ typedef struct sendflags {
 	/* show progress (ie. -v) */
 	boolean_t progress;
 
+	/* large blocks (>128K) are permitted */
+	boolean_t largeblock;
+
 	/* WRITE_EMBEDDED records of type DATA are permitted */
 	boolean_t embed_data;
 } sendflags_t;
diff --git a/include/libzfs_core.h b/include/libzfs_core.h
index d7d767055..bdd6c951e 100644
--- a/include/libzfs_core.h
+++ b/include/libzfs_core.h
@@ -53,7 +53,8 @@ int lzc_release(nvlist_t *, nvlist_t **);
 int lzc_get_holds(const char *, nvlist_t **);
 
 enum lzc_send_flags {
-	LZC_SEND_FLAG_EMBED_DATA = 1 << 0
+	LZC_SEND_FLAG_EMBED_DATA = 1 << 0,
+	LZC_SEND_FLAG_LARGE_BLOCK = 1 << 1
 };
 
 int lzc_send(const char *, const char *, int, enum lzc_send_flags);
diff --git a/include/sys/dmu.h b/include/sys/dmu.h
index aa3e89d60..08871e890 100644
--- a/include/sys/dmu.h
+++ b/include/sys/dmu.h
@@ -245,7 +245,7 @@ void zfs_znode_byteswap(void *buf, size_t size);
  * The maximum number of bytes that can be accessed as part of one
  * operation, including metadata.
  */
-#define	DMU_MAX_ACCESS (10<<20) /* 10MB */
+#define	DMU_MAX_ACCESS (64 * 1024 * 1024) /* 64MB */
 #define	DMU_MAX_DELETEBLKCNT (20480) /* ~5MB of indirect blocks */
 
 #define	DMU_USERUSED_OBJECT	(-1ULL)
@@ -732,6 +732,7 @@ void xuio_stat_wbuf_copied(void);
 void xuio_stat_wbuf_nocopy(void);
 
 extern int zfs_prefetch_disable;
+extern int zfs_max_recordsize;
 
 /*
  * Asynchronously try to read in the data.
diff --git a/include/sys/dmu_objset.h b/include/sys/dmu_objset.h
index 65ae850f4..8cb7bd02f 100644
--- a/include/sys/dmu_objset.h
+++ b/include/sys/dmu_objset.h
@@ -99,6 +99,7 @@ struct objset {
 	zfs_cache_type_t os_secondary_cache;
 	zfs_sync_type_t os_sync;
 	zfs_redundant_metadata_type_t os_redundant_metadata;
+	int os_recordsize;
 
 	/* no lock needed: */
 	struct dmu_tx *os_synctx; /* XXX sketchy */
diff --git a/include/sys/dmu_send.h b/include/sys/dmu_send.h
index dc183c02c..3a8dc89ab 100644
--- a/include/sys/dmu_send.h
+++ b/include/sys/dmu_send.h
@@ -37,12 +37,14 @@ struct dsl_dataset;
 struct drr_begin;
 struct avl_tree;
 
-int dmu_send(const char *tosnap, const char *fromsnap, boolean_t embedok,
+int dmu_send(const char *tosnap, const char *fromsnap,
+    boolean_t embedok, boolean_t large_block_ok,
     int outfd, struct vnode *vp, offset_t *off);
 int dmu_send_estimate(struct dsl_dataset *ds, struct dsl_dataset *fromds,
     uint64_t *sizep);
 int dmu_send_obj(const char *pool, uint64_t tosnap, uint64_t fromsnap,
-    boolean_t embedok, int outfd, vnode_t *vp, offset_t *off);
+    boolean_t embedok, boolean_t large_block_ok,
+    int outfd, struct vnode *vp, offset_t *off);
 
 typedef struct dmu_recv_cookie {
 	struct dsl_dataset *drc_ds;
diff --git a/include/sys/dsl_dataset.h b/include/sys/dsl_dataset.h
index edfc5509e..1985ce824 100644
--- a/include/sys/dsl_dataset.h
+++ b/include/sys/dsl_dataset.h
@@ -84,6 +84,13 @@ struct dsl_pool;
 #define	DS_FIELD_BOOKMARK_NAMES "com.delphix:bookmarks"
 
 /*
+ * This field is present (with value=0) if this dataset may contain large
+ * blocks (>128KB).  If it is present, then this dataset
+ * is counted in the refcount of the SPA_FEATURE_LARGE_BLOCKS feature.
+ */
+#define	DS_FIELD_LARGE_BLOCKS "org.open-zfs:large_blocks"
+
+/*
  * DS_FLAG_CI_DATASET is set if the dataset contains a file system whose
  * name lookups should be performed case-insensitively.
  */
@@ -138,6 +145,8 @@ typedef struct dsl_dataset {
 	/* only used in syncing context, only valid for non-snapshots: */
 	struct dsl_dataset *ds_prev;
 	uint64_t ds_bookmarks;  /* DMU_OTN_ZAP_METADATA */
+	boolean_t ds_large_blocks;
+	boolean_t ds_need_large_blocks;
 
 	/* has internal locking: */
 	dsl_deadlist_t ds_deadlist;
@@ -252,6 +261,8 @@ int dsl_dataset_space_written(dsl_dataset_t *oldsnap, dsl_dataset_t *new,
 int dsl_dataset_space_wouldfree(dsl_dataset_t *firstsnap, dsl_dataset_t *last,
     uint64_t *usedp, uint64_t *compp, uint64_t *uncompp);
 boolean_t dsl_dataset_is_dirty(dsl_dataset_t *ds);
+int dsl_dataset_activate_large_blocks(const char *dsname);
+void dsl_dataset_activate_large_blocks_sync_impl(uint64_t dsobj, dmu_tx_t *tx);
 
 int dsl_dsobj_to_dsname(char *pname, uint64_t obj, char *buf);
 
diff --git a/include/sys/fs/zfs.h b/include/sys/fs/zfs.h
index 87a91fef0..4da144c72 100644
--- a/include/sys/fs/zfs.h
+++ b/include/sys/fs/zfs.h
@@ -200,6 +200,7 @@ typedef enum {
 	ZPOOL_PROP_FREEING,
 	ZPOOL_PROP_FRAGMENTATION,
 	ZPOOL_PROP_LEAKED,
+	ZPOOL_PROP_MAXBLOCKSIZE,
 	ZPOOL_PROP_TNAME,
 	ZPOOL_NUM_PROPS
 } zpool_prop_t;
diff --git a/include/sys/spa.h b/include/sys/spa.h
index 834ad005a..5dc9084da 100644
--- a/include/sys/spa.h
+++ b/include/sys/spa.h
@@ -98,17 +98,26 @@ _NOTE(CONSTCOND) } while (0)
 _NOTE(CONSTCOND) } while (0)
 
 /*
- * We currently support nine block sizes, from 512 bytes to 128K.
- * We could go higher, but the benefits are near-zero and the cost
- * of COWing a giant block to modify one byte would become excessive.
+ * We currently support block sizes from 512 bytes to 16MB.
+ * The benefits of larger blocks, and thus larger IO, need to be weighed
+ * against the cost of COWing a giant block to modify one byte, and the
+ * large latency of reading or writing a large block.
+ *
+ * Note that although blocks up to 16MB are supported, the recordsize
+ * property can not be set larger than zfs_max_recordsize (default 1MB).
+ * See the comment near zfs_max_recordsize in dsl_dataset.c for details.
+ *
+ * Note that although the LSIZE field of the blkptr_t can store sizes up
+ * to 32MB, the dnode's dn_datablkszsec can only store sizes up to
+ * 32MB - 512 bytes.  Therefore, we limit SPA_MAXBLOCKSIZE to 16MB.
  */
 #define	SPA_MINBLOCKSHIFT	9
-#define	SPA_MAXBLOCKSHIFT	17
+#define	SPA_OLD_MAXBLOCKSHIFT	17
+#define	SPA_MAXBLOCKSHIFT	24
 #define	SPA_MINBLOCKSIZE	(1ULL << SPA_MINBLOCKSHIFT)
+#define	SPA_OLD_MAXBLOCKSIZE	(1ULL << SPA_OLD_MAXBLOCKSHIFT)
 #define	SPA_MAXBLOCKSIZE	(1ULL << SPA_MAXBLOCKSHIFT)
 
-#define	SPA_BLOCKSIZES		(SPA_MAXBLOCKSHIFT - SPA_MINBLOCKSHIFT + 1)
-
 /*
  * Size of block to hold the configuration data (a packed nvlist)
  */
@@ -830,6 +839,7 @@ extern boolean_t spa_has_slogs(spa_t *spa);
 extern boolean_t spa_is_root(spa_t *spa);
 extern boolean_t spa_writeable(spa_t *spa);
 extern boolean_t spa_has_pending_synctask(spa_t *spa);
+extern int spa_maxblocksize(spa_t *spa);
 extern void zfs_blkptr_verify(spa_t *spa, const blkptr_t *bp);
 
 extern int spa_mode(spa_t *spa);
diff --git a/include/sys/zap_impl.h b/include/sys/zap_impl.h
index 528402f79..bfd43e31d 100644
--- a/include/sys/zap_impl.h
+++ b/include/sys/zap_impl.h
@@ -42,8 +42,7 @@ extern int fzap_default_block_shift;
 
 #define	MZAP_ENT_LEN		64
 #define	MZAP_NAME_LEN		(MZAP_ENT_LEN - 8 - 4 - 2)
-#define	MZAP_MAX_BLKSHIFT	SPA_MAXBLOCKSHIFT
-#define	MZAP_MAX_BLKSZ		(1 << MZAP_MAX_BLKSHIFT)
+#define	MZAP_MAX_BLKSZ		SPA_OLD_MAXBLOCKSIZE
 
 #define	ZAP_NEED_CD		(-1U)
 
diff --git a/include/sys/zfs_ioctl.h b/include/sys/zfs_ioctl.h
index 5cfdcc50f..c71ceb9c5 100644
--- a/include/sys/zfs_ioctl.h
+++ b/include/sys/zfs_ioctl.h
@@ -96,13 +96,16 @@ typedef enum drr_headertype {
 /* flags #3 - #15 are reserved for incompatible closed-source implementations */
 #define	DMU_BACKUP_FEATURE_EMBED_DATA		(1<<16)
 #define	DMU_BACKUP_FEATURE_EMBED_DATA_LZ4	(1<<17)
+/* flag #18 is reserved for a Delphix feature */
+#define	DMU_BACKUP_FEATURE_LARGE_BLOCKS		(1<<19)
 
 /*
  * Mask of all supported backup features
  */
 #define	DMU_BACKUP_FEATURE_MASK	(DMU_BACKUP_FEATURE_DEDUP | \
     DMU_BACKUP_FEATURE_DEDUPPROPS | DMU_BACKUP_FEATURE_SA_SPILL | \
-    DMU_BACKUP_FEATURE_EMBED_DATA | DMU_BACKUP_FEATURE_EMBED_DATA_LZ4)
+    DMU_BACKUP_FEATURE_EMBED_DATA | DMU_BACKUP_FEATURE_EMBED_DATA_LZ4 | \
+    DMU_BACKUP_FEATURE_LARGE_BLOCKS)
 
 /* Are all features in the given flag word currently supported? */
 #define	DMU_STREAM_SUPPORTED(x)	(!((x) & ~DMU_BACKUP_FEATURE_MASK))
diff --git a/include/sys/zfs_sa.h b/include/sys/zfs_sa.h
index 735d4b32a..06c4d589a 100644
--- a/include/sys/zfs_sa.h
+++ b/include/sys/zfs_sa.h
@@ -129,7 +129,7 @@ typedef struct znode_phys {
 #ifdef _KERNEL
 
 #define	DXATTR_MAX_ENTRY_SIZE	(32768)
-#define	DXATTR_MAX_SA_SIZE	(SPA_MAXBLOCKSIZE >> 1)
+#define	DXATTR_MAX_SA_SIZE	(SPA_OLD_MAXBLOCKSIZE >> 1)
 
 int zfs_sa_readlink(struct znode *, uio_t *);
 void zfs_sa_symlink(struct znode *, char *link, int len, dmu_tx_t *);
diff --git a/include/sys/zfs_znode.h b/include/sys/zfs_znode.h
index a6b82d574..79ca4f7e9 100644
--- a/include/sys/zfs_znode.h
+++ b/include/sys/zfs_znode.h
@@ -137,8 +137,6 @@ extern "C" {
 #define	ZFS_SHARES_DIR		"SHARES"
 #define	ZFS_SA_ATTRS		"SA_ATTRS"
 
-#define	ZFS_MAX_BLOCKSIZE	(SPA_MAXBLOCKSIZE)
-
 /*
  * Path component length
  *
diff --git a/include/sys/zil.h b/include/sys/zil.h
index 9c806964d..362304135 100644
--- a/include/sys/zil.h
+++ b/include/sys/zil.h
@@ -90,7 +90,6 @@ typedef struct zil_chain {
 } zil_chain_t;
 
 #define	ZIL_MIN_BLKSZ	4096ULL
-#define	ZIL_MAX_BLKSZ	SPA_MAXBLOCKSIZE
 
 /*
  * The words of a log block checksum.
diff --git a/include/sys/zil_impl.h b/include/sys/zil_impl.h
index 0db4b525c..0c426a15d 100644
--- a/include/sys/zil_impl.h
+++ b/include/sys/zil_impl.h
@@ -140,7 +140,7 @@ typedef struct zil_bp_node {
 	avl_node_t	zn_node;
 } zil_bp_node_t;
 
-#define	ZIL_MAX_LOG_DATA (SPA_MAXBLOCKSIZE - sizeof (zil_chain_t) - \
+#define	ZIL_MAX_LOG_DATA (SPA_OLD_MAXBLOCKSIZE - sizeof (zil_chain_t) - \
     sizeof (lr_write_t))
 
 #ifdef	__cplusplus
diff --git a/include/zfeature_common.h b/include/zfeature_common.h
index e3215bebd..e383c4ff7 100644
--- a/include/zfeature_common.h
+++ b/include/zfeature_common.h
@@ -49,6 +49,7 @@ typedef enum spa_feature {
 	SPA_FEATURE_EMBEDDED_DATA,
 	SPA_FEATURE_BOOKMARKS,
 	SPA_FEATURE_FS_SS_LIMIT,
+	SPA_FEATURE_LARGE_BLOCKS,
 	SPA_FEATURES
 } spa_feature_t;
 
diff --git a/lib/libzfs/libzfs_dataset.c b/lib/libzfs/libzfs_dataset.c
index 4087baf34..9f23d1801 100644
--- a/lib/libzfs/libzfs_dataset.c
+++ b/lib/libzfs/libzfs_dataset.c
@@ -1055,21 +1055,28 @@ zfs_valid_proplist(libzfs_handle_t *hdl, zfs_type_t type, nvlist_t *nvl,
 			break;
 		}
 
-		case ZFS_PROP_RECORDSIZE:
 		case ZFS_PROP_VOLBLOCKSIZE:
-			/* must be power of two within SPA_{MIN,MAX}BLOCKSIZE */
+		case ZFS_PROP_RECORDSIZE:
+		{
+			int maxbs = SPA_MAXBLOCKSIZE;
+			if (zhp != NULL) {
+				maxbs = zpool_get_prop_int(zhp->zpool_hdl,
+				    ZPOOL_PROP_MAXBLOCKSIZE, NULL);
+			}
+			/*
+			 * The value must be a power of two between
+			 * SPA_MINBLOCKSIZE and maxbs.
+			 */
 			if (intval < SPA_MINBLOCKSIZE ||
-			    intval > SPA_MAXBLOCKSIZE || !ISP2(intval)) {
+			    intval > maxbs || !ISP2(intval)) {
 				zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
-				    "'%s' must be power of 2 from %u "
-				    "to %uk"), propname,
-				    (uint_t)SPA_MINBLOCKSIZE,
-				    (uint_t)SPA_MAXBLOCKSIZE >> 10);
+				    "'%s' must be power of 2 from 512B "
+				    "to %uKB"), propname, maxbs >> 10);
 				(void) zfs_error(hdl, EZFS_BADPROP, errbuf);
 				goto error;
 			}
 			break;
-
+		}
 		case ZFS_PROP_MLSLABEL:
 		{
 #ifdef HAVE_MLSLABEL
@@ -1446,7 +1453,8 @@ zfs_setprop_error(libzfs_handle_t *hdl, zfs_prop_t prop, int err,
 		break;
 
 	case ERANGE:
-		if (prop == ZFS_PROP_COMPRESSION) {
+		if (prop == ZFS_PROP_COMPRESSION ||
+		    prop == ZFS_PROP_RECORDSIZE) {
 			(void) zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
 			    "property setting is not allowed on "
 			    "bootable datasets"));
@@ -3212,9 +3220,7 @@ zfs_create(libzfs_handle_t *hdl, const char *path, zfs_type_t type,
 		case EDOM:
 			zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
 			    "volume block size must be power of 2 from "
-			    "%u to %uk"),
-			    (uint_t)SPA_MINBLOCKSIZE,
-			    (uint_t)SPA_MAXBLOCKSIZE >> 10);
+			    "512B to %uKB"), zfs_max_recordsize >> 10);
 
 			return (zfs_error(hdl, EZFS_BADPROP, errbuf));
 
diff --git a/lib/libzfs/libzfs_sendrecv.c b/lib/libzfs/libzfs_sendrecv.c
index 8911e0ed2..cdc872caa 100644
--- a/lib/libzfs/libzfs_sendrecv.c
+++ b/lib/libzfs/libzfs_sendrecv.c
@@ -214,7 +214,7 @@ static void *
 cksummer(void *arg)
 {
 	dedup_arg_t *dda = arg;
-	char *buf = malloc(1<<20);
+	char *buf = zfs_alloc(dda->dedup_hdl, SPA_MAXBLOCKSIZE);
 	dmu_replay_record_t thedrr;
 	dmu_replay_record_t *drr = &thedrr;
 	struct drr_begin *drrb = &thedrr.drr_u.drr_begin;
@@ -279,9 +279,9 @@ cksummer(void *arg)
 			    DMU_COMPOUNDSTREAM && drr->drr_payloadlen != 0) {
 				int sz = drr->drr_payloadlen;
 
-				if (sz > 1<<20) {
-					free(buf);
-					buf = malloc(sz);
+				if (sz > SPA_MAXBLOCKSIZE) {
+					buf = zfs_realloc(dda->dedup_hdl, buf,
+					    SPA_MAXBLOCKSIZE, sz);
 				}
 				(void) ssread(buf, sz, ofp);
 				if (ferror(stdin))
@@ -834,7 +834,7 @@ typedef struct send_dump_data {
 	char prevsnap[ZFS_MAXNAMELEN];
 	uint64_t prevsnap_obj;
 	boolean_t seenfrom, seento, replicate, doall, fromorigin;
-	boolean_t verbose, dryrun, parsable, progress, embed_data;
+	boolean_t verbose, dryrun, parsable, progress, embed_data, large_block;
 	int outfd;
 	boolean_t err;
 	nvlist_t *fss;
@@ -1181,6 +1181,8 @@ dump_snapshot(zfs_handle_t *zhp, void *arg)
 		}
 
 		enum lzc_send_flags flags = 0;
+		if (sdd->large_block)
+			flags |= LZC_SEND_FLAG_LARGE_BLOCK;
 		if (sdd->embed_data)
 			flags |= LZC_SEND_FLAG_EMBED_DATA;
 
@@ -1529,6 +1531,7 @@ zfs_send(zfs_handle_t *zhp, const char *fromsnap, const char *tosnap,
 	sdd.parsable = flags->parsable;
 	sdd.progress = flags->progress;
 	sdd.dryrun = flags->dryrun;
+	sdd.large_block = flags->largeblock;
 	sdd.embed_data = flags->embed_data;
 	sdd.filter_cb = filter_func;
 	sdd.filter_cb_arg = cb_arg;
@@ -2564,7 +2567,7 @@ static int
 recv_skip(libzfs_handle_t *hdl, int fd, boolean_t byteswap)
 {
 	dmu_replay_record_t *drr;
-	void *buf = malloc(1<<20);
+	void *buf = zfs_alloc(hdl, SPA_MAXBLOCKSIZE);
 	char errbuf[1024];
 
 	(void) snprintf(errbuf, sizeof (errbuf), dgettext(TEXT_DOMAIN,
diff --git a/lib/libzfs_core/libzfs_core.c b/lib/libzfs_core/libzfs_core.c
index 2198ecd6f..69df5579b 100644
--- a/lib/libzfs_core/libzfs_core.c
+++ b/lib/libzfs_core/libzfs_core.c
@@ -455,6 +455,10 @@ lzc_get_holds(const char *snapname, nvlist_t **holdsp)
  *
  * "fd" is the file descriptor to write the send stream to.
  *
+ * If "flags" contains LZC_SEND_FLAG_LARGE_BLOCK, the stream is permitted
+ * to contain DRR_WRITE records with drr_length > 128K, and DRR_OBJECT
+ * records with drr_blksz > 128K.
+ *
  * If "flags" contains LZC_SEND_FLAG_EMBED_DATA, the stream is permitted
  * to contain DRR_WRITE_EMBEDDED records with drr_etype==BP_EMBEDDED_TYPE_DATA,
  * which the receiving system must support (as indicated by support
@@ -471,6 +475,8 @@ lzc_send(const char *snapname, const char *from, int fd,
 	fnvlist_add_int32(args, "fd", fd);
 	if (from != NULL)
 		fnvlist_add_string(args, "fromsnap", from);
+	if (flags & LZC_SEND_FLAG_LARGE_BLOCK)
+		fnvlist_add_boolean(args, "largeblockok");
 	if (flags & LZC_SEND_FLAG_EMBED_DATA)
 		fnvlist_add_boolean(args, "embedok");
 	err = lzc_ioctl(ZFS_IOC_SEND_NEW, snapname, args, NULL);
diff --git a/man/man5/zfs-module-parameters.5 b/man/man5/zfs-module-parameters.5
index 4bbfbf512..359e9f72f 100644
--- a/man/man5/zfs-module-parameters.5
+++ b/man/man5/zfs-module-parameters.5
@@ -948,6 +948,24 @@ Default value: \fB32,768\fR.
 .sp
 .ne 2
 .na
+\fBzfs_max_recordsize\fR (int)
+.ad
+.RS 12n
+We currently support block sizes from 512 bytes to 16MB.  The benefits of
+larger blocks, and thus larger IO, need to be weighed against the cost of
+COWing a giant block to modify one byte.  Additionally, very large blocks
+can have an impact on i/o latency, and also potentially on the memory
+allocator.  Therefore, we do not allow the recordsize to be set larger than
+zfs_max_recordsize (default 1MB).  Larger blocks can be created by changing
+this tunable, and pools with larger blocks can always be imported and used,
+regardless of this setting.
+.sp
+Default value: \fB1,048,576\fR.
+.RE
+
+.sp
+.ne 2
+.na
 \fBzfs_mdcomp_disable\fR (int)
 .ad
 .RS 12n
diff --git a/man/man5/zpool-features.5 b/man/man5/zpool-features.5
index 27034264b..a1dac4292 100644
--- a/man/man5/zpool-features.5
+++ b/man/man5/zpool-features.5
@@ -411,5 +411,26 @@ never return to being \fBenabled\fR.
 
 .RE
 
+.sp
+.ne 2
+.na
+\fB\fBlarge_blocks\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID	org.open-zfs:large_block
+READ\-ONLY COMPATIBLE	no
+DEPENDENCIES	extensible_dataset
+.TE
+
+The \fBlarge_block\fR feature allows the record size on a dataset to be
+set larger than 128KB.
+
+This feature becomes \fBactive\fR once a \fBrecordsize\fR property has been
+set larger than 128KB, and will return to being \fBenabled\fR once all
+filesystems that have ever had their recordsize larger than 128KB are destroyed.
+.RE
+
 .SH "SEE ALSO"
 \fBzpool\fR(8)
diff --git a/man/man8/zfs.8 b/man/man8/zfs.8
index 81fe726cd..f926f174a 100644
--- a/man/man8/zfs.8
+++ b/man/man8/zfs.8
@@ -174,12 +174,12 @@ zfs \- configures ZFS file systems
 
 .LP
 .nf
-\fBzfs\fR \fBsend\fR [\fB-DnPpRve\fR] [\fB-\fR[\fBiI\fR] \fIsnapshot\fR] \fIsnapshot\fR
+\fBzfs\fR \fBsend\fR [\fB-DnPpRveL\fR] [\fB-\fR[\fBiI\fR] \fIsnapshot\fR] \fIsnapshot\fR
 .fi
 
 .LP
 .nf
-\fBzfs\fR \fBsend\fR [\fB-e\fR] [\fB-i \fIsnapshot\fR|\fIbookmark\fR]\fR \fIfilesystem\fR|\fIvolume\fR|\fIsnapshot\fR
+\fBzfs\fR \fBsend\fR [\fB-eL\fR] [\fB-i \fIsnapshot\fR|\fIbookmark\fR]\fR \fIfilesystem\fR|\fIvolume\fR|\fIsnapshot\fR
 .fi
 
 .LP
@@ -2706,7 +2706,7 @@ See \fBzpool-features\fR(5) for details on ZFS feature flags and the
 .sp
 .ne 2
 .na
-\fBzfs send\fR [\fB-DnPpRve\fR] [\fB-\fR[\fBiI\fR] \fIsnapshot\fR] \fIsnapshot\fR
+\fBzfs send\fR [\fB-DnPpRveL\fR] [\fB-\fR[\fBiI\fR] \fIsnapshot\fR] \fIsnapshot\fR
 .ad
 .sp .6
 .RS 4n
@@ -2763,6 +2763,22 @@ Generate a deduplicated stream. Blocks which would have been sent multiple times
 .ne 2
 .mk
 .na
+\fB\fB-L\fR\fR
+.ad
+.sp .6
+.RS 4n
+Generate a stream which may contain blocks larger than 128KB.  This flag
+has no effect if the \fBlarge_blocks\fR pool feature is disabled, or if
+the \fRrecordsize\fR property of this filesystem has never been set above
+128KB.  The receiving system must have the \fBlarge_blocks\fR pool feature
+enabled as well.  See \fBzpool-features\fR(5) for details on ZFS feature
+flags and the \fBlarge_blocks\fR feature.
+.RE
+
+.sp
+.ne 2
+.mk
+.na
 \fB\fB-e\fR\fR
 .ad
 .sp .6
@@ -2828,7 +2844,7 @@ The format of the stream is committed. You will be able to receive your streams
 .sp
 .ne 2
 .na
-\fBzfs send\fR [\fB-e\fR] [\fB-i\fR \fIsnapshot\fR|\fIbookmark\fR] \fIfilesystem\fR|\fIvolume\fR|\fIsnapshot\fR
+\fBzfs send\fR [\fB-eL\fR] [\fB-i\fR \fIsnapshot\fR|\fIbookmark\fR] \fIfilesystem\fR|\fIvolume\fR|\fIsnapshot\fR
 .ad
 .sp .6
 .RS 4n
@@ -2860,6 +2876,22 @@ or the origin's origin, etc.
 .ne 2
 .mk
 .na
+\fB\fB-L\fR\fR
+.ad
+.sp .6
+.RS 4n
+Generate a stream which may contain blocks larger than 128KB.  This flag
+has no effect if the \fBlarge_blocks\fR pool feature is disabled, or if
+the \fRrecordsize\fR property of this filesystem has never been set above
+128KB.  The receiving system must have the \fBlarge_blocks\fR pool feature
+enabled as well.  See \fBzpool-features\fR(5) for details on ZFS feature
+flags and the \fBlarge_blocks\fR feature.
+.RE
+
+.sp
+.ne 2
+.mk
+.na
 \fB\fB-e\fR\fR
 .ad
 .sp .6
@@ -2909,7 +2941,6 @@ The \fB-d\fR and \fB-e\fR options cause the file system name of the target snaps
 Discard the first element of the sent snapshot's file system name, using the remaining elements to determine the name of the target file system for the new snapshot as described in the paragraph above.
 .RE
 
-
 .sp
 .ne 2
 .na
diff --git a/module/zcommon/zfs_prop.c b/module/zcommon/zfs_prop.c
index 70f1d93df..aaebab444 100644
--- a/module/zcommon/zfs_prop.c
+++ b/module/zcommon/zfs_prop.c
@@ -426,8 +426,8 @@ zfs_prop_init(void)
 
 	/* inherit number properties */
 	zprop_register_number(ZFS_PROP_RECORDSIZE, "recordsize",
-	    SPA_MAXBLOCKSIZE, PROP_INHERIT,
-	    ZFS_TYPE_FILESYSTEM, "512 to 128k, power of 2", "RECSIZE");
+	    SPA_OLD_MAXBLOCKSIZE, PROP_INHERIT,
+	    ZFS_TYPE_FILESYSTEM, "512 to 1M, power of 2", "RECSIZE");
 
 	/* hidden properties */
 	zprop_register_hidden(ZFS_PROP_CREATETXG, "createtxg", PROP_TYPE_NUMBER,
diff --git a/module/zcommon/zpool_prop.c b/module/zcommon/zpool_prop.c
index e5f69c815..910c56dcc 100644
--- a/module/zcommon/zpool_prop.c
+++ b/module/zcommon/zpool_prop.c
@@ -131,6 +131,8 @@ zpool_prop_init(void)
 	/* hidden properties */
 	zprop_register_hidden(ZPOOL_PROP_NAME, "name", PROP_TYPE_STRING,
 	    PROP_READONLY, ZFS_TYPE_POOL, "NAME");
+	zprop_register_hidden(ZPOOL_PROP_MAXBLOCKSIZE, "maxblocksize",
+	    PROP_TYPE_NUMBER, PROP_READONLY, ZFS_TYPE_POOL, "MAXBLOCKSIZE");
 	zprop_register_hidden(ZPOOL_PROP_TNAME, "tname", PROP_TYPE_STRING,
 	    PROP_ONETIME, ZFS_TYPE_POOL, "TNAME");
 }
diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 6975ada62..1699ea7e7 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -1329,7 +1329,7 @@ arc_buf_alloc(spa_t *spa, uint64_t size, void *tag, arc_buf_contents_t type)
 	arc_buf_hdr_t *hdr;
 	arc_buf_t *buf;
 
-	VERIFY3U(size, <=, SPA_MAXBLOCKSIZE);
+	VERIFY3U(size, <=, spa_maxblocksize(spa));
 	hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
 	ASSERT(BUF_EMPTY(hdr));
 	hdr->b_size = size;
@@ -3289,7 +3289,7 @@ top:
 		 * Gracefully handle a damaged logical block size as a
 		 * checksum error by passing a dummy zio to the done callback.
 		 */
-		if (size > SPA_MAXBLOCKSIZE) {
+		if (size > spa_maxblocksize(spa)) {
 			if (done) {
 				rzio = zio_null(pio, spa, NULL,
 				    NULL, NULL, zio_flags);
diff --git a/module/zfs/bpobj.c b/module/zfs/bpobj.c
index 25767e83f..ebfdc2e7a 100644
--- a/module/zfs/bpobj.c
+++ b/module/zfs/bpobj.c
@@ -43,7 +43,7 @@ bpobj_alloc_empty(objset_t *os, int blocksize, dmu_tx_t *tx)
 		if (!spa_feature_is_active(spa, SPA_FEATURE_EMPTY_BPOBJ)) {
 			ASSERT0(dp->dp_empty_bpobj);
 			dp->dp_empty_bpobj =
-			    bpobj_alloc(os, SPA_MAXBLOCKSIZE, tx);
+			    bpobj_alloc(os, SPA_OLD_MAXBLOCKSIZE, tx);
 			VERIFY(zap_add(os,
 			    DMU_POOL_DIRECTORY_OBJECT,
 			    DMU_POOL_EMPTY_BPOBJ, sizeof (uint64_t), 1,
@@ -399,7 +399,8 @@ bpobj_enqueue_subobj(bpobj_t *bpo, uint64_t subobj, dmu_tx_t *tx)
 	dmu_buf_will_dirty(bpo->bpo_dbuf, tx);
 	if (bpo->bpo_phys->bpo_subobjs == 0) {
 		bpo->bpo_phys->bpo_subobjs = dmu_object_alloc(bpo->bpo_os,
-		    DMU_OT_BPOBJ_SUBOBJ, SPA_MAXBLOCKSIZE, DMU_OT_NONE, 0, tx);
+		    DMU_OT_BPOBJ_SUBOBJ, SPA_OLD_MAXBLOCKSIZE,
+		    DMU_OT_NONE, 0, tx);
 	}
 
 	ASSERT0(dmu_object_info(bpo->bpo_os, bpo->bpo_phys->bpo_subobjs, &doi));
diff --git a/module/zfs/bptree.c b/module/zfs/bptree.c
index d6ea9d7c6..9f62d7b91 100644
--- a/module/zfs/bptree.c
+++ b/module/zfs/bptree.c
@@ -65,7 +65,7 @@ bptree_alloc(objset_t *os, dmu_tx_t *tx)
 	bptree_phys_t *bt;
 
 	obj = dmu_object_alloc(os, DMU_OTN_UINT64_METADATA,
-	    SPA_MAXBLOCKSIZE, DMU_OTN_UINT64_METADATA,
+	    SPA_OLD_MAXBLOCKSIZE, DMU_OTN_UINT64_METADATA,
 	    sizeof (bptree_phys_t), tx);
 
 	/*
diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index cd74ce3e8..7d8adcd73 100644
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -2216,10 +2216,8 @@ dbuf_spill_set_blksz(dmu_buf_t *db_fake, uint64_t blksz, dmu_tx_t *tx)
 		return (SET_ERROR(ENOTSUP));
 	if (blksz == 0)
 		blksz = SPA_MINBLOCKSIZE;
-	if (blksz > SPA_MAXBLOCKSIZE)
-		blksz = SPA_MAXBLOCKSIZE;
-	else
-		blksz = P2ROUNDUP(blksz, SPA_MINBLOCKSIZE);
+	ASSERT3U(blksz, <=, spa_maxblocksize(dmu_objset_spa(db->db_objset)));
+	blksz = P2ROUNDUP(blksz, SPA_MINBLOCKSIZE);
 
 	DB_DNODE_ENTER(db);
 	dn = DB_DNODE(db);
diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c
index 6d42bf8a2..ae4e1dd21 100644
--- a/module/zfs/dmu_objset.c
+++ b/module/zfs/dmu_objset.c
@@ -256,6 +256,14 @@ logbias_changed_cb(void *arg, uint64_t newval)
 		zil_set_logbias(os->os_zil, newval);
 }
 
+static void
+recordsize_changed_cb(void *arg, uint64_t newval)
+{
+	objset_t *os = arg;
+
+	os->os_recordsize = newval;
+}
+
 void
 dmu_objset_byteswap(void *buf, size_t size)
 {
@@ -385,6 +393,11 @@ dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
 				    ZFS_PROP_REDUNDANT_METADATA),
 				    redundant_metadata_changed_cb, os);
 			}
+			if (err == 0) {
+				err = dsl_prop_register(ds,
+				    zfs_prop_to_name(ZFS_PROP_RECORDSIZE),
+				    recordsize_changed_cb, os);
+			}
 		}
 		if (err != 0) {
 			VERIFY(arc_buf_remove_ref(os->os_phys_buf,
@@ -660,6 +673,9 @@ dmu_objset_evict(objset_t *os)
 			VERIFY0(dsl_prop_unregister(ds,
 			    zfs_prop_to_name(ZFS_PROP_REDUNDANT_METADATA),
 			    redundant_metadata_changed_cb, os));
+			VERIFY0(dsl_prop_unregister(ds,
+			    zfs_prop_to_name(ZFS_PROP_RECORDSIZE),
+			    recordsize_changed_cb, os));
 		}
 		VERIFY0(dsl_prop_unregister(ds,
 		    zfs_prop_to_name(ZFS_PROP_PRIMARYCACHE),
diff --git a/module/zfs/dmu_send.c b/module/zfs/dmu_send.c
index c1cac2e67..e26d344d6 100644
--- a/module/zfs/dmu_send.c
+++ b/module/zfs/dmu_send.c
@@ -234,11 +234,12 @@ dump_write(dmu_sendarg_t *dsp, dmu_object_type_t type,
 	drrw->drr_offset = offset;
 	drrw->drr_length = blksz;
 	drrw->drr_toguid = dsp->dsa_toguid;
-	if (BP_IS_EMBEDDED(bp)) {
+	if (bp == NULL || BP_IS_EMBEDDED(bp)) {
 		/*
-		 * There's no pre-computed checksum of embedded BP's, so
-		 * (like fletcher4-checkummed blocks) userland will have
-		 * to compute a dedup-capable checksum itself.
+		 * There's no pre-computed checksum for partial-block
+		 * writes or embedded BP's, so (like
+		 * fletcher4-checkummed blocks) userland will have to
+		 * compute a dedup-capable checksum itself.
 		 */
 		drrw->drr_checksumtype = ZIO_CHECKSUM_OFF;
 	} else {
@@ -400,6 +401,10 @@ dump_dnode(dmu_sendarg_t *dsp, uint64_t object, dnode_phys_t *dnp)
 	drro->drr_compress = dnp->dn_compress;
 	drro->drr_toguid = dsp->dsa_toguid;
 
+	if (!(dsp->dsa_featureflags & DMU_BACKUP_FEATURE_LARGE_BLOCKS) &&
+	    drro->drr_blksz > SPA_OLD_MAXBLOCKSIZE)
+		drro->drr_blksz = SPA_OLD_MAXBLOCKSIZE;
+
 	if (dump_bytes(dsp, dsp->dsa_drr, sizeof (dmu_replay_record_t)) != 0)
 		return (SET_ERROR(EINTR));
 
@@ -517,6 +522,7 @@ backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 		    zb->zb_blkid * blksz, blksz, bp);
 	} else { /* it's a level-0 block of a regular object */
 		uint32_t aflags = ARC_WAIT;
+		uint64_t offset;
 		arc_buf_t *abuf;
 		int blksz = BP_GET_LSIZE(bp);
 
@@ -539,8 +545,24 @@ backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 			}
 		}
 
-		err = dump_write(dsp, type, zb->zb_object, zb->zb_blkid * blksz,
-		    blksz, bp, abuf->b_data);
+		offset = zb->zb_blkid * blksz;
+
+		if (!(dsp->dsa_featureflags &
+		    DMU_BACKUP_FEATURE_LARGE_BLOCKS) &&
+		    blksz > SPA_OLD_MAXBLOCKSIZE) {
+			char *buf = abuf->b_data;
+			while (blksz > 0 && err == 0) {
+				int n = MIN(blksz, SPA_OLD_MAXBLOCKSIZE);
+				err = dump_write(dsp, type, zb->zb_object,
+				    offset, n, NULL, buf);
+				offset += n;
+				buf += n;
+				blksz -= n;
+			}
+		} else {
+			err = dump_write(dsp, type, zb->zb_object,
+			    offset, blksz, bp, abuf->b_data);
+		}
 		(void) arc_buf_remove_ref(abuf, &abuf);
 	}
 
@@ -554,7 +576,7 @@ backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 static int
 dmu_send_impl(void *tag, dsl_pool_t *dp, dsl_dataset_t *ds,
     zfs_bookmark_phys_t *fromzb, boolean_t is_clone, boolean_t embedok,
-    int outfd, vnode_t *vp, offset_t *off)
+    boolean_t large_block_ok, int outfd, vnode_t *vp, offset_t *off)
 {
 	objset_t *os;
 	dmu_replay_record_t *drr;
@@ -589,6 +611,8 @@ dmu_send_impl(void *tag, dsl_pool_t *dp, dsl_dataset_t *ds,
 	}
 #endif
 
+	if (large_block_ok && ds->ds_large_blocks)
+		featureflags |= DMU_BACKUP_FEATURE_LARGE_BLOCKS;
 	if (embedok &&
 	    spa_feature_is_active(dp->dp_spa, SPA_FEATURE_EMBEDDED_DATA)) {
 		featureflags |= DMU_BACKUP_FEATURE_EMBED_DATA;
@@ -684,7 +708,8 @@ out:
 
 int
 dmu_send_obj(const char *pool, uint64_t tosnap, uint64_t fromsnap,
-    boolean_t embedok, int outfd, vnode_t *vp, offset_t *off)
+    boolean_t embedok, boolean_t large_block_ok,
+    int outfd, vnode_t *vp, offset_t *off)
 {
 	dsl_pool_t *dp;
 	dsl_dataset_t *ds;
@@ -719,18 +744,19 @@ dmu_send_obj(const char *pool, uint64_t tosnap, uint64_t fromsnap,
 		zb.zbm_guid = dsl_dataset_phys(fromds)->ds_guid;
 		is_clone = (fromds->ds_dir != ds->ds_dir);
 		dsl_dataset_rele(fromds, FTAG);
-		err = dmu_send_impl(FTAG, dp, ds, &zb, is_clone, embedok,
-		    outfd, vp, off);
+		err = dmu_send_impl(FTAG, dp, ds, &zb, is_clone,
+		    embedok, large_block_ok, outfd, vp, off);
 	} else {
-		err = dmu_send_impl(FTAG, dp, ds, NULL, B_FALSE, embedok,
-		    outfd, vp, off);
+		err = dmu_send_impl(FTAG, dp, ds, NULL, B_FALSE,
+		    embedok, large_block_ok, outfd, vp, off);
 	}
 	dsl_dataset_rele(ds, FTAG);
 	return (err);
 }
 
 int
-dmu_send(const char *tosnap, const char *fromsnap, boolean_t embedok,
+dmu_send(const char *tosnap, const char *fromsnap,
+    boolean_t embedok, boolean_t large_block_ok,
     int outfd, vnode_t *vp, offset_t *off)
 {
 	dsl_pool_t *dp;
@@ -797,11 +823,11 @@ dmu_send(const char *tosnap, const char *fromsnap, boolean_t embedok,
 			dsl_pool_rele(dp, FTAG);
 			return (err);
 		}
-		err = dmu_send_impl(FTAG, dp, ds, &zb, is_clone, embedok,
-		    outfd, vp, off);
+		err = dmu_send_impl(FTAG, dp, ds, &zb, is_clone,
+		    embedok, large_block_ok, outfd, vp, off);
 	} else {
-		err = dmu_send_impl(FTAG, dp, ds, NULL, B_FALSE, embedok,
-		    outfd, vp, off);
+		err = dmu_send_impl(FTAG, dp, ds, NULL, B_FALSE,
+		    embedok, large_block_ok, outfd, vp, off);
 	}
 	if (owned)
 		dsl_dataset_disown(ds, FTAG);
@@ -1000,6 +1026,15 @@ dmu_recv_begin_check(void *arg, dmu_tx_t *tx)
 	    !spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_LZ4_COMPRESS))
 		return (SET_ERROR(ENOTSUP));
 
+	/*
+	 * The receiving code doesn't know how to translate large blocks
+	 * to smaller ones, so the pool must have the LARGE_BLOCKS
+	 * feature enabled if the stream has LARGE_BLOCKS.
+	 */
+	if ((featureflags & DMU_BACKUP_FEATURE_LARGE_BLOCKS) &&
+	    !spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_LARGE_BLOCKS))
+		return (SET_ERROR(ENOTSUP));
+
 	error = dsl_dataset_hold(dp, tofs, FTAG, &ds);
 	if (error == 0) {
 		/* target fs already exists; recv into temp clone */
@@ -1125,6 +1160,13 @@ dmu_recv_begin_sync(void *arg, dmu_tx_t *tx)
 	}
 	VERIFY0(dsl_dataset_own_obj(dp, dsobj, dmu_recv_tag, &newds));
 
+	if ((DMU_GET_FEATUREFLAGS(drrb->drr_versioninfo) &
+	    DMU_BACKUP_FEATURE_LARGE_BLOCKS) &&
+	    !newds->ds_large_blocks) {
+		dsl_dataset_activate_large_blocks_sync_impl(dsobj, tx);
+		newds->ds_large_blocks = B_TRUE;
+	}
+
 	dmu_buf_will_dirty(newds->ds_dbuf, tx);
 	dsl_dataset_phys(newds)->ds_flags |= DS_FLAG_INCONSISTENT;
 
@@ -1250,6 +1292,7 @@ restore_read(struct restorearg *ra, int len, char *buf)
 
 	/* some things will require 8-byte alignment, so everything must */
 	ASSERT0(len % 8);
+	ASSERT3U(len, <=, ra->bufsize);
 
 	while (done < len) {
 		ssize_t resid;
@@ -1391,7 +1434,7 @@ restore_object(struct restorearg *ra, objset_t *os, struct drr_object *drro)
 	    drro->drr_compress >= ZIO_COMPRESS_FUNCTIONS ||
 	    P2PHASE(drro->drr_blksz, SPA_MINBLOCKSIZE) ||
 	    drro->drr_blksz < SPA_MINBLOCKSIZE ||
-	    drro->drr_blksz > SPA_MAXBLOCKSIZE ||
+	    drro->drr_blksz > spa_maxblocksize(dmu_objset_spa(os)) ||
 	    drro->drr_bonuslen > DN_MAX_BONUSLEN) {
 		return (SET_ERROR(EINVAL));
 	}
@@ -1665,7 +1708,7 @@ restore_spill(struct restorearg *ra, objset_t *os, struct drr_spill *drrs)
 	int err;
 
 	if (drrs->drr_length < SPA_MINBLOCKSIZE ||
-	    drrs->drr_length > SPA_MAXBLOCKSIZE)
+	    drrs->drr_length > spa_maxblocksize(dmu_objset_spa(os)))
 		return (SET_ERROR(EINVAL));
 
 	data = restore_read(ra, drrs->drr_length, NULL);
@@ -1752,7 +1795,7 @@ dmu_recv_stream(dmu_recv_cookie_t *drc, vnode_t *vp, offset_t *voffp,
 	ra.cksum = drc->drc_cksum;
 	ra.vp = vp;
 	ra.voff = *voffp;
-	ra.bufsize = 1<<20;
+	ra.bufsize = SPA_MAXBLOCKSIZE;
 	ra.buf = vmem_alloc(ra.bufsize, KM_SLEEP);
 
 	/* these were verified in dmu_recv_begin */
diff --git a/module/zfs/dmu_tx.c b/module/zfs/dmu_tx.c
index 89f45a781..62a8d471e 100644
--- a/module/zfs/dmu_tx.c
+++ b/module/zfs/dmu_tx.c
@@ -241,7 +241,7 @@ dmu_tx_count_write(dmu_tx_hold_t *txh, uint64_t off, uint64_t len)
 		return;
 
 	min_bs = SPA_MINBLOCKSHIFT;
-	max_bs = SPA_MAXBLOCKSHIFT;
+	max_bs = highbit64(txh->txh_tx->tx_objset->os_recordsize) - 1;
 	min_ibs = DN_MIN_INDBLKSHIFT;
 	max_ibs = DN_MAX_INDBLKSHIFT;
 
@@ -310,6 +310,14 @@ dmu_tx_count_write(dmu_tx_hold_t *txh, uint64_t off, uint64_t len)
 			 */
 			ASSERT(dn->dn_datablkshift != 0);
 			min_bs = max_bs = dn->dn_datablkshift;
+		} else {
+			/*
+			 * The blocksize can increase up to the recordsize,
+			 * or if it is already more than the recordsize,
+			 * up to the next power of 2.
+			 */
+			min_bs = highbit64(dn->dn_datablksz - 1);
+			max_bs = MAX(max_bs, highbit64(dn->dn_datablksz - 1));
 		}
 
 		/*
@@ -745,11 +753,11 @@ dmu_tx_hold_zap(dmu_tx_t *tx, uint64_t object, int add, const char *name)
 		bp = &dn->dn_phys->dn_blkptr[0];
 		if (dsl_dataset_block_freeable(dn->dn_objset->os_dsl_dataset,
 		    bp, bp->blk_birth))
-			txh->txh_space_tooverwrite += SPA_MAXBLOCKSIZE;
+			txh->txh_space_tooverwrite += MZAP_MAX_BLKSZ;
 		else
-			txh->txh_space_towrite += SPA_MAXBLOCKSIZE;
+			txh->txh_space_towrite += MZAP_MAX_BLKSZ;
 		if (!BP_IS_HOLE(bp))
-			txh->txh_space_tounref += SPA_MAXBLOCKSIZE;
+			txh->txh_space_tounref += MZAP_MAX_BLKSZ;
 		return;
 	}
 
@@ -1546,18 +1554,18 @@ dmu_tx_hold_spill(dmu_tx_t *tx, uint64_t object)
 
 	/* If blkptr doesn't exist then add space to towrite */
 	if (!(dn->dn_phys->dn_flags & DNODE_FLAG_SPILL_BLKPTR)) {
-		txh->txh_space_towrite += SPA_MAXBLOCKSIZE;
+		txh->txh_space_towrite += SPA_OLD_MAXBLOCKSIZE;
 	} else {
 		blkptr_t *bp;
 
 		bp = &dn->dn_phys->dn_spill;
 		if (dsl_dataset_block_freeable(dn->dn_objset->os_dsl_dataset,
 		    bp, bp->blk_birth))
-			txh->txh_space_tooverwrite += SPA_MAXBLOCKSIZE;
+			txh->txh_space_tooverwrite += SPA_OLD_MAXBLOCKSIZE;
 		else
-			txh->txh_space_towrite += SPA_MAXBLOCKSIZE;
+			txh->txh_space_towrite += SPA_OLD_MAXBLOCKSIZE;
 		if (!BP_IS_HOLE(bp))
-			txh->txh_space_tounref += SPA_MAXBLOCKSIZE;
+			txh->txh_space_tounref += SPA_OLD_MAXBLOCKSIZE;
 	}
 }
 
diff --git a/module/zfs/dnode.c b/module/zfs/dnode.c
index 235884931..e1ea165aa 100644
--- a/module/zfs/dnode.c
+++ b/module/zfs/dnode.c
@@ -540,10 +540,10 @@ dnode_allocate(dnode_t *dn, dmu_object_type_t ot, int blocksize, int ibs,
 {
 	int i;
 
+	ASSERT3U(blocksize, <=,
+	    spa_maxblocksize(dmu_objset_spa(dn->dn_objset)));
 	if (blocksize == 0)
 		blocksize = 1 << zfs_default_bs;
-	else if (blocksize > SPA_MAXBLOCKSIZE)
-		blocksize = SPA_MAXBLOCKSIZE;
 	else
 		blocksize = P2ROUNDUP(blocksize, SPA_MINBLOCKSIZE);
 
@@ -624,7 +624,8 @@ dnode_reallocate(dnode_t *dn, dmu_object_type_t ot, int blocksize,
 	int nblkptr;
 
 	ASSERT3U(blocksize, >=, SPA_MINBLOCKSIZE);
-	ASSERT3U(blocksize, <=, SPA_MAXBLOCKSIZE);
+	ASSERT3U(blocksize, <=,
+	    spa_maxblocksize(dmu_objset_spa(dn->dn_objset)));
 	ASSERT0(blocksize % SPA_MINBLOCKSIZE);
 	ASSERT(dn->dn_object != DMU_META_DNODE_OBJECT || dmu_tx_private_ok(tx));
 	ASSERT(tx->tx_txg != 0);
@@ -1377,10 +1378,9 @@ dnode_set_blksz(dnode_t *dn, uint64_t size, int ibs, dmu_tx_t *tx)
 	dmu_buf_impl_t *db;
 	int err;
 
+	ASSERT3U(size, <=, spa_maxblocksize(dmu_objset_spa(dn->dn_objset)));
 	if (size == 0)
 		size = SPA_MINBLOCKSIZE;
-	if (size > SPA_MAXBLOCKSIZE)
-		size = SPA_MAXBLOCKSIZE;
 	else
 		size = P2ROUNDUP(size, SPA_MINBLOCKSIZE);
 
diff --git a/module/zfs/dsl_dataset.c b/module/zfs/dsl_dataset.c
index b444fca64..9a66c6552 100644
--- a/module/zfs/dsl_dataset.c
+++ b/module/zfs/dsl_dataset.c
@@ -51,6 +51,17 @@
 #include <sys/dsl_userhold.h>
 #include <sys/dsl_bookmark.h>
 
+/*
+ * The SPA supports block sizes up to 16MB.  However, very large blocks
+ * can have an impact on i/o latency (e.g. tying up a spinning disk for
+ * ~300ms), and also potentially on the memory allocator.  Therefore,
+ * we do not allow the recordsize to be set larger than zfs_max_recordsize
+ * (default 1MB).  Larger blocks can be created by changing this tunable,
+ * and pools with larger blocks can always be imported and used, regardless
+ * of this setting.
+ */
+int zfs_max_recordsize = 1 * 1024 * 1024;
+
 #define	SWITCH64(x, y) \
 	{ \
 		uint64_t __tmp = (x); \
@@ -60,8 +71,6 @@
 
 #define	DS_REF_MAX	(1ULL << 62)
 
-#define	DSL_DEADLIST_BLOCKSIZE	SPA_MAXBLOCKSIZE
-
 extern inline dsl_dataset_phys_t *dsl_dataset_phys(dsl_dataset_t *ds);
 
 /*
@@ -117,6 +126,8 @@ dsl_dataset_block_born(dsl_dataset_t *ds, const blkptr_t *bp, dmu_tx_t *tx)
 	dsl_dataset_phys(ds)->ds_compressed_bytes += compressed;
 	dsl_dataset_phys(ds)->ds_uncompressed_bytes += uncompressed;
 	dsl_dataset_phys(ds)->ds_unique_bytes += used;
+	if (BP_GET_LSIZE(bp) > SPA_OLD_MAXBLOCKSIZE)
+		ds->ds_need_large_blocks = B_TRUE;
 	mutex_exit(&ds->ds_lock);
 	dsl_dir_diduse_space(ds->ds_dir, DD_USED_HEAD, delta,
 	    compressed, uncompressed, tx);
@@ -414,6 +425,14 @@ dsl_dataset_hold_obj(dsl_pool_t *dp, uint64_t dsobj, void *tag,
 		list_create(&ds->ds_sendstreams, sizeof (dmu_sendarg_t),
 		    offsetof(dmu_sendarg_t, dsa_link));
 
+		if (doi.doi_type == DMU_OTN_ZAP_METADATA) {
+			err = zap_contains(mos, dsobj, DS_FIELD_LARGE_BLOCKS);
+			if (err == 0)
+				ds->ds_large_blocks = B_TRUE;
+			else
+				ASSERT3U(err, ==, ENOENT);
+		}
+
 		if (err == 0) {
 			err = dsl_dir_hold_obj(dp,
 			    dsl_dataset_phys(ds)->ds_dir_obj, NULL, ds,
@@ -730,6 +749,9 @@ dsl_dataset_create_sync_dd(dsl_dir_t *dd, dsl_dataset_t *origin,
 		dsphys->ds_flags |= dsl_dataset_phys(origin)->ds_flags &
 		    (DS_FLAG_INCONSISTENT | DS_FLAG_CI_DATASET);
 
+		if (origin->ds_large_blocks)
+			dsl_dataset_activate_large_blocks_sync_impl(dsobj, tx);
+
 		dmu_buf_will_dirty(origin->ds_dbuf, tx);
 		dsl_dataset_phys(origin)->ds_num_children++;
 
@@ -1253,6 +1275,9 @@ dsl_dataset_snapshot_sync_impl(dsl_dataset_t *ds, const char *snapname,
 	dsphys->ds_bp = dsl_dataset_phys(ds)->ds_bp;
 	dmu_buf_rele(dbuf, FTAG);
 
+	if (ds->ds_large_blocks)
+		dsl_dataset_activate_large_blocks_sync_impl(dsobj, tx);
+
 	ASSERT3U(ds->ds_prev != 0, ==,
 	    dsl_dataset_phys(ds)->ds_prev_snap_obj != 0);
 	if (ds->ds_prev) {
@@ -1541,6 +1566,11 @@ dsl_dataset_sync(dsl_dataset_t *ds, zio_t *zio, dmu_tx_t *tx)
 	dsl_dataset_phys(ds)->ds_fsid_guid = ds->ds_fsid_guid;
 
 	dmu_objset_sync(ds->ds_objset, zio, tx);
+
+	if (ds->ds_need_large_blocks && !ds->ds_large_blocks) {
+		dsl_dataset_activate_large_blocks_sync_impl(ds->ds_object, tx);
+		ds->ds_large_blocks = B_TRUE;
+	}
 }
 
 static void
@@ -3222,6 +3252,77 @@ dsl_dataset_space_wouldfree(dsl_dataset_t *firstsnap,
 	return (err);
 }
 
+static int
+dsl_dataset_activate_large_blocks_check(void *arg, dmu_tx_t *tx)
+{
+	const char *dsname = arg;
+	dsl_dataset_t *ds;
+	dsl_pool_t *dp = dmu_tx_pool(tx);
+	int error = 0;
+
+	if (!spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_LARGE_BLOCKS))
+		return (SET_ERROR(ENOTSUP));
+
+	ASSERT(spa_feature_is_enabled(dp->dp_spa,
+	    SPA_FEATURE_EXTENSIBLE_DATASET));
+
+	error = dsl_dataset_hold(dp, dsname, FTAG, &ds);
+	if (error != 0)
+		return (error);
+
+	if (ds->ds_large_blocks)
+		error = EALREADY;
+	dsl_dataset_rele(ds, FTAG);
+
+	return (error);
+}
+
+void
+dsl_dataset_activate_large_blocks_sync_impl(uint64_t dsobj, dmu_tx_t *tx)
+{
+	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
+	objset_t *mos = dmu_tx_pool(tx)->dp_meta_objset;
+	uint64_t zero = 0;
+
+	spa_feature_incr(spa, SPA_FEATURE_LARGE_BLOCKS, tx);
+	dmu_object_zapify(mos, dsobj, DMU_OT_DSL_DATASET, tx);
+
+	VERIFY0(zap_add(mos, dsobj, DS_FIELD_LARGE_BLOCKS,
+	    sizeof (zero), 1, &zero, tx));
+}
+
+static void
+dsl_dataset_activate_large_blocks_sync(void *arg, dmu_tx_t *tx)
+{
+	const char *dsname = arg;
+	dsl_dataset_t *ds;
+
+	VERIFY0(dsl_dataset_hold(dmu_tx_pool(tx), dsname, FTAG, &ds));
+
+	dsl_dataset_activate_large_blocks_sync_impl(ds->ds_object, tx);
+	ASSERT(!ds->ds_large_blocks);
+	ds->ds_large_blocks = B_TRUE;
+	dsl_dataset_rele(ds, FTAG);
+}
+
+int
+dsl_dataset_activate_large_blocks(const char *dsname)
+{
+	int error;
+
+	error = dsl_sync_task(dsname,
+	    dsl_dataset_activate_large_blocks_check,
+	    dsl_dataset_activate_large_blocks_sync, (void *)dsname,
+	    1, ZFS_SPACE_CHECK_RESERVED);
+
+	/*
+	 * EALREADY indicates that this dataset already supports large blocks.
+	 */
+	if (error == EALREADY)
+		error = 0;
+	return (error);
+}
+
 /*
  * Return TRUE if 'earlier' is an earlier snapshot in 'later's timeline.
  * For example, they could both be snapshots of the same filesystem, and
@@ -3275,6 +3376,15 @@ dsl_dataset_zapify(dsl_dataset_t *ds, dmu_tx_t *tx)
 }
 
 #if defined(_KERNEL) && defined(HAVE_SPL)
+#if defined(_LP64)
+module_param(zfs_max_recordsize, int, 0644);
+MODULE_PARM_DESC(zfs_max_recordsize, "Max allowed record size");
+#else
+/* Limited to 1M on 32-bit platforms due to lack of virtual address space */
+module_param(zfs_max_recordsize, int, 0444);
+MODULE_PARM_DESC(zfs_max_recordsize, "Max allowed record size");
+#endif
+
 EXPORT_SYMBOL(dsl_dataset_hold);
 EXPORT_SYMBOL(dsl_dataset_hold_obj);
 EXPORT_SYMBOL(dsl_dataset_own);
diff --git a/module/zfs/dsl_deadlist.c b/module/zfs/dsl_deadlist.c
index 55810f5c3..8da77ebd7 100644
--- a/module/zfs/dsl_deadlist.c
+++ b/module/zfs/dsl_deadlist.c
@@ -148,7 +148,7 @@ uint64_t
 dsl_deadlist_alloc(objset_t *os, dmu_tx_t *tx)
 {
 	if (spa_version(dmu_objset_spa(os)) < SPA_VERSION_DEADLISTS)
-		return (bpobj_alloc(os, SPA_MAXBLOCKSIZE, tx));
+		return (bpobj_alloc(os, SPA_OLD_MAXBLOCKSIZE, tx));
 	return (zap_create(os, DMU_OT_DEADLIST, DMU_OT_DEADLIST_HDR,
 	    sizeof (dsl_deadlist_phys_t), tx));
 }
@@ -185,7 +185,7 @@ dle_enqueue(dsl_deadlist_t *dl, dsl_deadlist_entry_t *dle,
 {
 	if (dle->dle_bpobj.bpo_object ==
 	    dmu_objset_pool(dl->dl_os)->dp_empty_bpobj) {
-		uint64_t obj = bpobj_alloc(dl->dl_os, SPA_MAXBLOCKSIZE, tx);
+		uint64_t obj = bpobj_alloc(dl->dl_os, SPA_OLD_MAXBLOCKSIZE, tx);
 		bpobj_close(&dle->dle_bpobj);
 		bpobj_decr_empty(dl->dl_os, tx);
 		VERIFY3U(0, ==, bpobj_open(&dle->dle_bpobj, dl->dl_os, obj));
@@ -259,7 +259,7 @@ dsl_deadlist_add_key(dsl_deadlist_t *dl, uint64_t mintxg, dmu_tx_t *tx)
 
 	dle = kmem_alloc(sizeof (*dle), KM_SLEEP);
 	dle->dle_mintxg = mintxg;
-	obj = bpobj_alloc_empty(dl->dl_os, SPA_MAXBLOCKSIZE, tx);
+	obj = bpobj_alloc_empty(dl->dl_os, SPA_OLD_MAXBLOCKSIZE, tx);
 	VERIFY3U(0, ==, bpobj_open(&dle->dle_bpobj, dl->dl_os, obj));
 	avl_add(&dl->dl_tree, dle);
 
@@ -344,7 +344,7 @@ dsl_deadlist_clone(dsl_deadlist_t *dl, uint64_t maxtxg,
 		if (dle->dle_mintxg >= maxtxg)
 			break;
 
-		obj = bpobj_alloc_empty(dl->dl_os, SPA_MAXBLOCKSIZE, tx);
+		obj = bpobj_alloc_empty(dl->dl_os, SPA_OLD_MAXBLOCKSIZE, tx);
 		VERIFY3U(0, ==, zap_add_int_key(dl->dl_os, newobj,
 		    dle->dle_mintxg, obj, tx));
 	}
diff --git a/module/zfs/dsl_destroy.c b/module/zfs/dsl_destroy.c
index 4623f5dd5..0e2238f99 100644
--- a/module/zfs/dsl_destroy.c
+++ b/module/zfs/dsl_destroy.c
@@ -277,6 +277,10 @@ dsl_destroy_snapshot_sync_impl(dsl_dataset_t *ds, boolean_t defer, dmu_tx_t *tx)
 
 	obj = ds->ds_object;
 
+	if (ds->ds_large_blocks) {
+		ASSERT0(zap_contains(mos, obj, DS_FIELD_LARGE_BLOCKS));
+		spa_feature_decr(dp->dp_spa, SPA_FEATURE_LARGE_BLOCKS, tx);
+	}
 	if (dsl_dataset_phys(ds)->ds_prev_snap_obj != 0) {
 		ASSERT3P(ds->ds_prev, ==, NULL);
 		VERIFY0(dsl_dataset_hold_obj(dp,
@@ -738,6 +742,9 @@ dsl_destroy_head_sync_impl(dsl_dataset_t *ds, dmu_tx_t *tx)
 		ASSERT0(ds->ds_reserved);
 	}
 
+	if (ds->ds_large_blocks)
+		spa_feature_decr(dp->dp_spa, SPA_FEATURE_LARGE_BLOCKS, tx);
+
 	dsl_scan_ds_destroyed(ds, tx);
 
 	obj = ds->ds_object;
diff --git a/module/zfs/dsl_pool.c b/module/zfs/dsl_pool.c
index fe1a4d8b7..13961918e 100644
--- a/module/zfs/dsl_pool.c
+++ b/module/zfs/dsl_pool.c
@@ -372,7 +372,7 @@ dsl_pool_create(spa_t *spa, nvlist_t *zplprops, uint64_t txg)
 		    FREE_DIR_NAME, &dp->dp_free_dir));
 
 		/* create and open the free_bplist */
-		obj = bpobj_alloc(dp->dp_meta_objset, SPA_MAXBLOCKSIZE, tx);
+		obj = bpobj_alloc(dp->dp_meta_objset, SPA_OLD_MAXBLOCKSIZE, tx);
 		VERIFY(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
 		    DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj, tx) == 0);
 		VERIFY0(bpobj_open(&dp->dp_free_bpobj,
@@ -804,7 +804,7 @@ dsl_pool_upgrade_dir_clones(dsl_pool_t *dp, dmu_tx_t *tx)
 	 * subobj support.  So call dmu_object_alloc() directly.
 	 */
 	obj = dmu_object_alloc(dp->dp_meta_objset, DMU_OT_BPOBJ,
-	    SPA_MAXBLOCKSIZE, DMU_OT_BPOBJ_HDR, sizeof (bpobj_phys_t), tx);
+	    SPA_OLD_MAXBLOCKSIZE, DMU_OT_BPOBJ_HDR, sizeof (bpobj_phys_t), tx);
 	VERIFY0(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
 	    DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj, tx));
 	VERIFY0(bpobj_open(&dp->dp_free_bpobj, dp->dp_meta_objset, obj));
diff --git a/module/zfs/sa.c b/module/zfs/sa.c
index 8e857e129..a3fcea87b 100644
--- a/module/zfs/sa.c
+++ b/module/zfs/sa.c
@@ -504,7 +504,7 @@ sa_resize_spill(sa_handle_t *hdl, uint32_t size, dmu_tx_t *tx)
 
 	if (size == 0) {
 		blocksize = SPA_MINBLOCKSIZE;
-	} else if (size > SPA_MAXBLOCKSIZE) {
+	} else if (size > SPA_OLD_MAXBLOCKSIZE) {
 		ASSERT(0);
 		return (SET_ERROR(EFBIG));
 	} else {
@@ -693,7 +693,7 @@ sa_build_layouts(sa_handle_t *hdl, sa_bulk_attr_t *attr_desc, int attr_count,
 	hdrsize = sa_find_sizes(sa, attr_desc, attr_count, hdl->sa_bonus,
 	    SA_BONUS, &spill_idx, &used, &spilling);
 
-	if (used > SPA_MAXBLOCKSIZE)
+	if (used > SPA_OLD_MAXBLOCKSIZE)
 		return (SET_ERROR(EFBIG));
 
 	VERIFY(0 == dmu_set_bonus(hdl->sa_bonus, spilling ?
@@ -717,7 +717,7 @@ sa_build_layouts(sa_handle_t *hdl, sa_bulk_attr_t *attr_desc, int attr_count,
 		    attr_count - spill_idx, hdl->sa_spill, SA_SPILL, &i,
 		    &spill_used, &dummy);
 
-		if (spill_used > SPA_MAXBLOCKSIZE)
+		if (spill_used > SPA_OLD_MAXBLOCKSIZE)
 			return (SET_ERROR(EFBIG));
 
 		if (BUF_SPACE_NEEDED(spill_used, spillhdrsize) >
diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index 3312c301c..2a9ef9ce5 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -266,6 +266,14 @@ spa_prop_get_config(spa_t *spa, nvlist_t **nvp)
 		spa_prop_add_list(*nvp, ZPOOL_PROP_ALTROOT, spa->spa_root,
 		    0, ZPROP_SRC_LOCAL);
 
+	if (spa_feature_is_enabled(spa, SPA_FEATURE_LARGE_BLOCKS)) {
+		spa_prop_add_list(*nvp, ZPOOL_PROP_MAXBLOCKSIZE, NULL,
+		    MIN(zfs_max_recordsize, SPA_MAXBLOCKSIZE), ZPROP_SRC_NONE);
+	} else {
+		spa_prop_add_list(*nvp, ZPOOL_PROP_MAXBLOCKSIZE, NULL,
+		    SPA_OLD_MAXBLOCKSIZE, ZPROP_SRC_NONE);
+	}
+
 	if ((dp = list_head(&spa->spa_config_list)) != NULL) {
 		if (dp->scd_path == NULL) {
 			spa_prop_add_list(*nvp, ZPOOL_PROP_CACHEFILE,
@@ -482,7 +490,7 @@ spa_prop_validate(spa_t *spa, nvlist_t *props)
 
 			if (!error) {
 				objset_t *os;
-				uint64_t compress;
+				uint64_t propval;
 
 				if (strval == NULL || strval[0] == '\0') {
 					objnum = zpool_prop_default_numeric(
@@ -494,15 +502,25 @@ spa_prop_validate(spa_t *spa, nvlist_t *props)
 				if (error)
 					break;
 
-				/* Must be ZPL and not gzip compressed. */
+				/*
+				 * Must be ZPL, and its property settings
+				 * must be supported by GRUB (compression
+				 * is not gzip, and large blocks are not used).
+				 */
 
 				if (dmu_objset_type(os) != DMU_OST_ZFS) {
 					error = SET_ERROR(ENOTSUP);
 				} else if ((error =
 				    dsl_prop_get_int_ds(dmu_objset_ds(os),
 				    zfs_prop_to_name(ZFS_PROP_COMPRESSION),
-				    &compress)) == 0 &&
-				    !BOOTFS_COMPRESS_VALID(compress)) {
+				    &propval)) == 0 &&
+				    !BOOTFS_COMPRESS_VALID(propval)) {
+					error = SET_ERROR(ENOTSUP);
+				} else if ((error =
+				    dsl_prop_get_int_ds(dmu_objset_ds(os),
+				    zfs_prop_to_name(ZFS_PROP_RECORDSIZE),
+				    &propval)) == 0 &&
+				    propval > SPA_OLD_MAXBLOCKSIZE) {
 					error = SET_ERROR(ENOTSUP);
 				} else {
 					objnum = dmu_objset_id(os);
diff --git a/module/zfs/spa_history.c b/module/zfs/spa_history.c
index 1041c8f57..01aa4641e 100644
--- a/module/zfs/spa_history.c
+++ b/module/zfs/spa_history.c
@@ -89,7 +89,7 @@ spa_history_create_obj(spa_t *spa, dmu_tx_t *tx)
 
 	ASSERT(spa->spa_history == 0);
 	spa->spa_history = dmu_object_alloc(mos, DMU_OT_SPA_HISTORY,
-	    SPA_MAXBLOCKSIZE, DMU_OT_SPA_HISTORY_OFFSETS,
+	    SPA_OLD_MAXBLOCKSIZE, DMU_OT_SPA_HISTORY_OFFSETS,
 	    sizeof (spa_history_phys_t), tx);
 
 	VERIFY(zap_add(mos, DMU_POOL_DIRECTORY_OBJECT,
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index 8e5fa683e..b46b2d0a4 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -1985,6 +1985,15 @@ spa_debug_enabled(spa_t *spa)
 	return (spa->spa_debug);
 }
 
+int
+spa_maxblocksize(spa_t *spa)
+{
+	if (spa_feature_is_enabled(spa, SPA_FEATURE_LARGE_BLOCKS))
+		return (SPA_MAXBLOCKSIZE);
+	else
+		return (SPA_OLD_MAXBLOCKSIZE);
+}
+
 #if defined(_KERNEL) && defined(HAVE_SPL)
 /* Namespace manipulation */
 EXPORT_SYMBOL(spa_lookup);
@@ -2040,6 +2049,7 @@ EXPORT_SYMBOL(spa_suspended);
 EXPORT_SYMBOL(spa_bootfs);
 EXPORT_SYMBOL(spa_delegation);
 EXPORT_SYMBOL(spa_meta_objset);
+EXPORT_SYMBOL(spa_maxblocksize);
 
 /* Miscellaneous support routines */
 EXPORT_SYMBOL(spa_rename);
diff --git a/module/zfs/vdev.c b/module/zfs/vdev.c
index 52198261e..fe6631925 100644
--- a/module/zfs/vdev.c
+++ b/module/zfs/vdev.c
@@ -847,9 +847,9 @@ vdev_metaslab_init(vdev_t *vd, uint64_t txg)
 
 	/*
 	 * Compute the raidz-deflation ratio.  Note, we hard-code
-	 * in 128k (1 << 17) because it is the current "typical" blocksize.
-	 * Even if SPA_MAXBLOCKSIZE changes, this algorithm must never change,
-	 * or we will inconsistently account for existing bp's.
+	 * in 128k (1 << 17) because it is the "typical" blocksize.
+	 * Even though SPA_MAXBLOCKSIZE changed, this algorithm can not change,
+	 * otherwise it would inconsistently account for existing bp's.
 	 */
 	vd->vdev_deflate_ratio = (1 << 17) /
 	    (vdev_psize_to_asize(vd, 1 << 17) >> SPA_MINBLOCKSHIFT);
diff --git a/module/zfs/vdev_disk.c b/module/zfs/vdev_disk.c
index db13b7bc4..0196f3945 100644
--- a/module/zfs/vdev_disk.c
+++ b/module/zfs/vdev_disk.c
@@ -552,9 +552,9 @@ retry:
 			goto retry;
 		}
 
-		dr->dr_bio[i] = bio_alloc(GFP_NOIO,
-		    bio_nr_pages(bio_ptr, bio_size));
 		/* bio_alloc() with __GFP_WAIT never returns NULL */
+		dr->dr_bio[i] = bio_alloc(GFP_NOIO,
+		    MIN(bio_nr_pages(bio_ptr, bio_size), BIO_MAX_PAGES));
 		if (unlikely(dr->dr_bio[i] == NULL)) {
 			vdev_disk_dio_free(dr);
 			return (ENOMEM);
diff --git a/module/zfs/vdev_queue.c b/module/zfs/vdev_queue.c
index cf0301649..a0d6fc4e3 100644
--- a/module/zfs/vdev_queue.c
+++ b/module/zfs/vdev_queue.c
@@ -167,7 +167,7 @@ int zfs_vdev_async_write_active_max_dirty_percent = 60;
  * we include spans of optional I/Os to aid aggregation at the disk even when
  * they aren't able to help us aggregate at this level.
  */
-int zfs_vdev_aggregation_limit = SPA_MAXBLOCKSIZE;
+int zfs_vdev_aggregation_limit = SPA_OLD_MAXBLOCKSIZE;
 int zfs_vdev_read_gap_limit = 32 << 10;
 int zfs_vdev_write_gap_limit = 4 << 10;
 
diff --git a/module/zfs/zap_micro.c b/module/zfs/zap_micro.c
index 5af98c2bc..8d920c2fa 100644
--- a/module/zfs/zap_micro.c
+++ b/module/zfs/zap_micro.c
@@ -34,6 +34,7 @@
 #include <sys/zap_leaf.h>
 #include <sys/avl.h>
 #include <sys/arc.h>
+#include <sys/dmu_objset.h>
 
 #ifdef _KERNEL
 #include <sys/sunddi.h>
@@ -654,9 +655,9 @@ zap_create_flags(objset_t *os, int normflags, zap_flags_t flags,
 	uint64_t obj = dmu_object_alloc(os, ot, 0, bonustype, bonuslen, tx);
 
 	ASSERT(leaf_blockshift >= SPA_MINBLOCKSHIFT &&
-	    leaf_blockshift <= SPA_MAXBLOCKSHIFT &&
+	    leaf_blockshift <= SPA_OLD_MAXBLOCKSHIFT &&
 	    indirect_blockshift >= SPA_MINBLOCKSHIFT &&
-	    indirect_blockshift <= SPA_MAXBLOCKSHIFT);
+	    indirect_blockshift <= SPA_OLD_MAXBLOCKSHIFT);
 
 	VERIFY(dmu_object_set_blocksize(os, obj,
 	    1ULL << leaf_blockshift, indirect_blockshift, tx) == 0);
@@ -1347,7 +1348,6 @@ zap_count_write(objset_t *os, uint64_t zapobj, const char *name, int add,
 	zap_t *zap;
 	int err = 0;
 
-
 	/*
 	 * Since, we don't have a name, we cannot figure out which blocks will
 	 * be affected in this operation. So, account for the worst case :
@@ -1360,7 +1360,7 @@ zap_count_write(objset_t *os, uint64_t zapobj, const char *name, int add,
 	 * large microzap results in a promotion to fatzap.
 	 */
 	if (name == NULL) {
-		*towrite += (3 + (add ? 4 : 0)) * SPA_MAXBLOCKSIZE;
+		*towrite += (3 + (add ? 4 : 0)) * SPA_OLD_MAXBLOCKSIZE;
 		return (err);
 	}
 
@@ -1384,7 +1384,7 @@ zap_count_write(objset_t *os, uint64_t zapobj, const char *name, int add,
 			/*
 			 * We treat this case as similar to (name == NULL)
 			 */
-			*towrite += (3 + (add ? 4 : 0)) * SPA_MAXBLOCKSIZE;
+			*towrite += (3 + (add ? 4 : 0)) * SPA_OLD_MAXBLOCKSIZE;
 		}
 	} else {
 		/*
@@ -1403,12 +1403,12 @@ zap_count_write(objset_t *os, uint64_t zapobj, const char *name, int add,
 		 *			ptrtbl blocks
 		 */
 		if (dmu_buf_freeable(zap->zap_dbuf))
-			*tooverwrite += SPA_MAXBLOCKSIZE;
+			*tooverwrite += MZAP_MAX_BLKSZ;
 		else
-			*towrite += SPA_MAXBLOCKSIZE;
+			*towrite += MZAP_MAX_BLKSZ;
 
 		if (add) {
-			*towrite += 4 * SPA_MAXBLOCKSIZE;
+			*towrite += 4 * MZAP_MAX_BLKSZ;
 		}
 	}
 
diff --git a/module/zfs/zfeature_common.c b/module/zfs/zfeature_common.c
index 461456275..609a72ab3 100644
--- a/module/zfs/zfeature_common.c
+++ b/module/zfs/zfeature_common.c
@@ -56,7 +56,8 @@ valid_char(char c, boolean_t after_colon)
 {
 	return ((c >= 'a' && c <= 'z') ||
 	    (c >= '0' && c <= '9') ||
-	    c == (after_colon ? '_' : '.'));
+	    (after_colon && c == '_') ||
+	    (!after_colon && (c == '.' || c == '-')));
 }
 
 /*
@@ -230,4 +231,15 @@ zpool_feature_init(void)
 	    "com.delphix:embedded_data", "embedded_data",
 	    "Blocks which compress very well use even less space.",
 	    B_FALSE, B_TRUE, B_TRUE, NULL);
+
+	{
+	static const spa_feature_t large_blocks_deps[] = {
+		SPA_FEATURE_EXTENSIBLE_DATASET,
+		SPA_FEATURE_NONE
+	};
+	zfeature_register(SPA_FEATURE_LARGE_BLOCKS,
+	    "org.open-zfs:large_blocks", "large_blocks",
+	    "Support for blocks larger than 128KB.", B_FALSE, B_FALSE, B_FALSE,
+	    large_blocks_deps);
+	}
 }
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index caaa3a21c..f5137d09e 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -2392,7 +2392,7 @@ zfs_prop_set_special(const char *dsname, zprop_source_t source,
 	const char *propname = nvpair_name(pair);
 	zfs_prop_t prop = zfs_name_to_prop(propname);
 	uint64_t intval;
-	int err;
+	int err = -1;
 
 	if (prop == ZPROP_INVAL) {
 		if (zfs_prop_userquota(propname))
@@ -3790,8 +3790,7 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
 		 * the SPA supports it. We ignore any errors here since
 		 * we'll catch them later.
 		 */
-		if (nvpair_type(pair) == DATA_TYPE_UINT64 &&
-		    nvpair_value_uint64(pair, &intval) == 0) {
+		if (nvpair_value_uint64(pair, &intval) == 0) {
 			if (intval >= ZIO_COMPRESS_GZIP_1 &&
 			    intval <= ZIO_COMPRESS_GZIP_9 &&
 			    zfs_earlier_version(dsname,
@@ -3842,6 +3841,42 @@ zfs_check_settable(const char *dsname, nvpair_t *pair, cred_t *cr)
 			return (SET_ERROR(ENOTSUP));
 		break;
 
+	case ZFS_PROP_RECORDSIZE:
+		/* Record sizes above 128k need the feature to be enabled */
+		if (nvpair_value_uint64(pair, &intval) == 0 &&
+		    intval > SPA_OLD_MAXBLOCKSIZE) {
+			spa_t *spa;
+
+			/*
+			 * If this is a bootable dataset then
+			 * the we don't allow large (>128K) blocks,
+			 * because GRUB doesn't support them.
+			 */
+			if (zfs_is_bootfs(dsname) &&
+			    intval > SPA_OLD_MAXBLOCKSIZE) {
+				return (SET_ERROR(EDOM));
+			}
+
+			/*
+			 * We don't allow setting the property above 1MB,
+			 * unless the tunable has been changed.
+			 */
+			if (intval > zfs_max_recordsize ||
+			    intval > SPA_MAXBLOCKSIZE)
+				return (SET_ERROR(EDOM));
+
+			if ((err = spa_open(dsname, &spa, FTAG)) != 0)
+				return (err);
+
+			if (!spa_feature_is_enabled(spa,
+			    SPA_FEATURE_LARGE_BLOCKS)) {
+				spa_close(spa, FTAG);
+				return (SET_ERROR(ENOTSUP));
+			}
+			spa_close(spa, FTAG);
+		}
+		break;
+
 	case ZFS_PROP_SHARESMB:
 		if (zpl_earlier_version(dsname, ZPL_VERSION_FUID))
 			return (SET_ERROR(ENOTSUP));
@@ -4221,7 +4256,7 @@ out:
  * zc_fromobj	objsetid of incremental fromsnap (may be zero)
  * zc_guid	if set, estimate size of stream only.  zc_cookie is ignored.
  *		output size in zc_objset_type.
- * zc_flags	if =1, WRITE_EMBEDDED records are permitted
+ * zc_flags	lzc_send_flags
  *
  * outputs:
  * zc_objset_type	estimated size, if zc_guid is set
@@ -4233,6 +4268,7 @@ zfs_ioc_send(zfs_cmd_t *zc)
 	offset_t off;
 	boolean_t estimate = (zc->zc_guid != 0);
 	boolean_t embedok = (zc->zc_flags & 0x1);
+	boolean_t large_block_ok = (zc->zc_flags & 0x2);
 
 	if (zc->zc_obj != 0) {
 		dsl_pool_t *dp;
@@ -4294,7 +4330,8 @@ zfs_ioc_send(zfs_cmd_t *zc)
 
 		off = fp->f_offset;
 		error = dmu_send_obj(zc->zc_name, zc->zc_sendobj,
-		    zc->zc_fromobj, embedok, zc->zc_cookie, fp->f_vnode, &off);
+		    zc->zc_fromobj, embedok, large_block_ok,
+		    zc->zc_cookie, fp->f_vnode, &off);
 
 		if (VOP_SEEK(fp->f_vnode, fp->f_offset, &off, NULL) == 0)
 			fp->f_offset = off;
@@ -5160,6 +5197,8 @@ zfs_ioc_space_snaps(const char *lastsnap, nvlist_t *innvl, nvlist_t *outnvl)
  * innvl: {
  *     "fd" -> file descriptor to write stream to (int32)
  *     (optional) "fromsnap" -> full snap name to send an incremental from
+ *     (optional) "largeblockok" -> (value ignored)
+ *         indicates that blocks > 128KB are permitted
  *     (optional) "embedok" -> (value ignored)
  *         presence indicates DRR_WRITE_EMBEDDED records are permitted
  * }
@@ -5175,6 +5214,7 @@ zfs_ioc_send_new(const char *snapname, nvlist_t *innvl, nvlist_t *outnvl)
 	char *fromname = NULL;
 	int fd;
 	file_t *fp;
+	boolean_t largeblockok;
 	boolean_t embedok;
 
 	error = nvlist_lookup_int32(innvl, "fd", &fd);
@@ -5183,13 +5223,15 @@ zfs_ioc_send_new(const char *snapname, nvlist_t *innvl, nvlist_t *outnvl)
 
 	(void) nvlist_lookup_string(innvl, "fromsnap", &fromname);
 
+	largeblockok = nvlist_exists(innvl, "largeblockok");
 	embedok = nvlist_exists(innvl, "embedok");
 
 	if ((fp = getf(fd)) == NULL)
 		return (SET_ERROR(EBADF));
 
 	off = fp->f_offset;
-	error = dmu_send(snapname, fromname, embedok, fd, fp->f_vnode, &off);
+	error = dmu_send(snapname, fromname, embedok, largeblockok,
+	    fd, fp->f_vnode, &off);
 
 	if (VOP_SEEK(fp->f_vnode, fp->f_offset, &off, NULL) == 0)
 		fp->f_offset = off;
diff --git a/module/zfs/zfs_log.c b/module/zfs/zfs_log.c
index cfce83138..38d8de0eb 100644
--- a/module/zfs/zfs_log.c
+++ b/module/zfs/zfs_log.c
@@ -492,7 +492,7 @@ zfs_log_write(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 		 * If the write would overflow the largest block then split it.
 		 */
 		if (write_state != WR_INDIRECT && resid > ZIL_MAX_LOG_DATA)
-			len = SPA_MAXBLOCKSIZE >> 1;
+			len = SPA_OLD_MAXBLOCKSIZE >> 1;
 		else
 			len = resid;
 
diff --git a/module/zfs/zfs_vfsops.c b/module/zfs/zfs_vfsops.c
index 59f73776c..e86b21aee 100644
--- a/module/zfs/zfs_vfsops.c
+++ b/module/zfs/zfs_vfsops.c
@@ -188,10 +188,9 @@ static void
 blksz_changed_cb(void *arg, uint64_t newval)
 {
 	zfs_sb_t *zsb = arg;
-
-	if (newval < SPA_MINBLOCKSIZE ||
-	    newval > SPA_MAXBLOCKSIZE || !ISP2(newval))
-		newval = SPA_MAXBLOCKSIZE;
+	ASSERT3U(newval, <=, spa_maxblocksize(dmu_objset_spa(zsb->z_os)));
+	ASSERT3U(newval, >=, SPA_MINBLOCKSIZE);
+	ASSERT(ISP2(newval));
 
 	zsb->z_max_blksz = newval;
 }
@@ -672,7 +671,7 @@ zfs_sb_create(const char *osname, zfs_sb_t **zsbp)
 	 */
 	zsb->z_sb = NULL;
 	zsb->z_parent = zsb;
-	zsb->z_max_blksz = SPA_MAXBLOCKSIZE;
+	zsb->z_max_blksz = SPA_OLD_MAXBLOCKSIZE;
 	zsb->z_show_ctldir = ZFS_SNAPDIR_VISIBLE;
 	zsb->z_os = os;
 
diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c
index 5ce8a1e98..19a4132e4 100644
--- a/module/zfs/zfs_vnops.c
+++ b/module/zfs/zfs_vnops.c
@@ -771,8 +771,14 @@ zfs_write(struct inode *ip, uio_t *uio, int ioflag, cred_t *cr)
 			uint64_t new_blksz;
 
 			if (zp->z_blksz > max_blksz) {
+				/*
+				 * File's blocksize is already larger than the
+				 * "recordsize" property.  Only let it grow to
+				 * the next power of 2.
+				 */
 				ASSERT(!ISP2(zp->z_blksz));
-				new_blksz = MIN(end_size, SPA_MAXBLOCKSIZE);
+				new_blksz = MIN(end_size,
+				    1 << highbit64(zp->z_blksz));
 			} else {
 				new_blksz = MIN(end_size, max_blksz);
 			}
diff --git a/module/zfs/zfs_znode.c b/module/zfs/zfs_znode.c
index a3d64fe01..f25ad0fc6 100644
--- a/module/zfs/zfs_znode.c
+++ b/module/zfs/zfs_znode.c
@@ -61,6 +61,7 @@
 #endif /* _KERNEL */
 
 #include <sys/dmu.h>
+#include <sys/dmu_objset.h>
 #include <sys/refcount.h>
 #include <sys/stat.h>
 #include <sys/zap.h>
@@ -1304,8 +1305,13 @@ zfs_extend(znode_t *zp, uint64_t end)
 		 * We are growing the file past the current block size.
 		 */
 		if (zp->z_blksz > ZTOZSB(zp)->z_max_blksz) {
+			/*
+			 * File's blocksize is already larger than the
+			 * "recordsize" property.  Only let it grow to
+			 * the next power of 2.
+			 */
 			ASSERT(!ISP2(zp->z_blksz));
-			newblksz = MIN(end, SPA_MAXBLOCKSIZE);
+			newblksz = MIN(end, 1 << highbit64(zp->z_blksz));
 		} else {
 			newblksz = MIN(end, ZTOZSB(zp)->z_max_blksz);
 		}
diff --git a/module/zfs/zil.c b/module/zfs/zil.c
index be1a86b24..3ae171e59 100644
--- a/module/zfs/zil.c
+++ b/module/zfs/zil.c
@@ -243,6 +243,7 @@ zil_read_log_block(zilog_t *zilog, const blkptr_t *bp, blkptr_t *nbp, void *dst,
 			    sizeof (cksum)) || BP_IS_HOLE(&zilc->zc_next_blk)) {
 				error = SET_ERROR(ECKSUM);
 			} else {
+				ASSERT3U(len, <=, SPA_OLD_MAXBLOCKSIZE);
 				bcopy(lr, dst, len);
 				*end = (char *)dst + len;
 				*nbp = zilc->zc_next_blk;
@@ -257,6 +258,8 @@ zil_read_log_block(zilog_t *zilog, const blkptr_t *bp, blkptr_t *nbp, void *dst,
 			    (zilc->zc_nused > (size - sizeof (*zilc)))) {
 				error = SET_ERROR(ECKSUM);
 			} else {
+				ASSERT3U(zilc->zc_nused, <=,
+				    SPA_OLD_MAXBLOCKSIZE);
 				bcopy(lr, dst, zilc->zc_nused);
 				*end = (char *)dst + zilc->zc_nused;
 				*nbp = zilc->zc_next_blk;
@@ -342,7 +345,7 @@ zil_parse(zilog_t *zilog, zil_parse_blk_func_t *parse_blk_func,
 	 * If the log has been claimed, stop if we encounter a sequence
 	 * number greater than the highest claimed sequence number.
 	 */
-	lrbuf = zio_buf_alloc(SPA_MAXBLOCKSIZE);
+	lrbuf = zio_buf_alloc(SPA_OLD_MAXBLOCKSIZE);
 	zil_bp_tree_init(zilog);
 
 	for (blk = zh->zh_log; !BP_IS_HOLE(&blk); blk = next_blk) {
@@ -389,7 +392,7 @@ done:
 	    (max_blk_seq == claim_blk_seq && max_lr_seq == claim_lr_seq));
 
 	zil_bp_tree_fini(zilog);
-	zio_buf_free(lrbuf, SPA_MAXBLOCKSIZE);
+	zio_buf_free(lrbuf, SPA_OLD_MAXBLOCKSIZE);
 
 	return (error);
 }
@@ -941,7 +944,7 @@ zil_lwb_write_init(zilog_t *zilog, lwb_t *lwb)
  *
  * These must be a multiple of 4KB. Note only the amount used (again
  * aligned to 4KB) actually gets written. However, we can't always just
- * allocate SPA_MAXBLOCKSIZE as the slog space could be exhausted.
+ * allocate SPA_OLD_MAXBLOCKSIZE as the slog space could be exhausted.
  */
 uint64_t zil_block_buckets[] = {
     4096,		/* non TX_WRITE */
@@ -1023,7 +1026,7 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb)
 		continue;
 	zil_blksz = zil_block_buckets[i];
 	if (zil_blksz == UINT64_MAX)
-		zil_blksz = SPA_MAXBLOCKSIZE;
+		zil_blksz = SPA_OLD_MAXBLOCKSIZE;
 	zilog->zl_prev_blks[zilog->zl_prev_rotor] = zil_blksz;
 	for (i = 0; i < ZIL_PREV_BLKS; i++)
 		zil_blksz = MAX(zil_blksz, zilog->zl_prev_blks[i]);
diff --git a/module/zfs/zio.c b/module/zfs/zio.c
index 9204df2b2..2b338f2a7 100644
--- a/module/zfs/zio.c
+++ b/module/zfs/zio.c
@@ -24,6 +24,7 @@
  * Copyright (c) 2011 Nexenta Systems, Inc. All rights reserved.
  */
 
+#include <sys/sysmacros.h>
 #include <sys/zfs_context.h>
 #include <sys/fm/fs/zfs.h>
 #include <sys/spa.h>
@@ -107,9 +108,8 @@ zio_init(void)
 
 	/*
 	 * For small buffers, we want a cache for each multiple of
-	 * SPA_MINBLOCKSIZE.  For medium-size buffers, we want a cache
-	 * for each quarter-power of 2.  For large buffers, we want
-	 * a cache for each multiple of PAGESIZE.
+	 * SPA_MINBLOCKSIZE.  For larger buffers, we want a cache
+	 * for each quarter-power of 2.
 	 */
 	for (c = 0; c < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; c++) {
 		size_t size = (c + 1) << SPA_MINBLOCKSHIFT;
@@ -117,7 +117,16 @@ zio_init(void)
 		size_t align = 0;
 		size_t cflags = (size > zio_buf_debug_limit) ? KMC_NODEBUG : 0;
 
-		while (p2 & (p2 - 1))
+#ifdef _ILP32
+		/*
+		 * Cache size limited to 1M on 32-bit platforms until ARC
+		 * buffers no longer require virtual address space.
+		 */
+		if (size > zfs_max_recordsize)
+			break;
+#endif
+
+		while (!ISP2(p2))
 			p2 &= p2 - 1;
 
 #ifndef _KERNEL
@@ -132,10 +141,8 @@ zio_init(void)
 #endif
 		if (size <= 4 * SPA_MINBLOCKSIZE) {
 			align = SPA_MINBLOCKSIZE;
-		} else if (IS_P2ALIGNED(size, PAGESIZE)) {
-			align = PAGESIZE;
 		} else if (IS_P2ALIGNED(size, p2 >> 2)) {
-			align = p2 >> 2;
+			align = MIN(p2 >> 2, PAGESIZE);
 		}
 
 		if (align != 0) {
@@ -174,6 +181,14 @@ zio_fini(void)
 	kmem_cache_t *last_data_cache = NULL;
 
 	for (c = 0; c < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; c++) {
+#ifdef _ILP32
+		/*
+		 * Cache size limited to 1M on 32-bit platforms until ARC
+		 * buffers no longer require virtual address space.
+		 */
+		if (((c + 1) << SPA_MINBLOCKSHIFT) > zfs_max_recordsize)
+			break;
+#endif
 		if (zio_buf_cache[c] != last_cache) {
 			last_cache = zio_buf_cache[c];
 			kmem_cache_destroy(zio_buf_cache[c]);