5162 zfs recv should use loaned arc buffer to avoid copy

Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Bayard Bell <Bayard.Bell@nexenta.com>
Reviewed by: Richard Elling <richard.elling@gmail.com>
Approved by: Garrett D'Amore <garrett@damore.org>

2 files changed, 37 insertions, 18 deletions

diff --git a/usr/src/uts/common/fs/zfs/dmu.c b/usr/src/uts/common/fs/zfs/dmu.c
index 619b3b4aa4..4fdcb14750 100644
--- a/usr/src/uts/common/fs/zfs/dmu.c
+++ b/usr/src/uts/common/fs/zfs/dmu.c
@@ -1264,7 +1264,14 @@ dmu_assign_arcbuf(dmu_buf_t *handle, uint64_t offset, arc_buf_t *buf,
 	rw_exit(&dn->dn_struct_rwlock);
 	DB_DNODE_EXIT(dbuf);
 
-	if (offset == db->db.db_offset && blksz == db->db.db_size) {
+	/*
+	 * We can only assign if the offset is aligned, the arc buf is the
+	 * same size as the dbuf, and the dbuf is not metadata.  It
+	 * can't be metadata because the loaned arc buf comes from the
+	 * user-data kmem arena.
+	 */
+	if (offset == db->db.db_offset && blksz == db->db.db_size &&
+	    DBUF_GET_BUFC_TYPE(db) == ARC_BUFC_DATA) {
 		dbuf_assign_arcbuf(db, buf, tx);
 		dbuf_rele(db, FTAG);
 	} else {
diff --git a/usr/src/uts/common/fs/zfs/dmu_send.c b/usr/src/uts/common/fs/zfs/dmu_send.c
index 97c9926bd7..9b03eff7a0 100644
--- a/usr/src/uts/common/fs/zfs/dmu_send.c
+++ b/usr/src/uts/common/fs/zfs/dmu_send.c
@@ -1212,11 +1212,13 @@ free_guid_map_onexit(void *arg)
 }
 
 static void *
-restore_read(struct restorearg *ra, int len)
+restore_read(struct restorearg *ra, int len, char *buf)
 {
-	void *rv;
 	int done = 0;
 
+	if (buf == NULL)
+		buf = ra->buf;
+
 	/* some things will require 8-byte alignment, so everything must */
 	ASSERT0(len % 8);
 
@@ -1224,7 +1226,7 @@ restore_read(struct restorearg *ra, int len)
 		ssize_t resid;
 
 		ra->err = vn_rdwr(UIO_READ, ra->vp,
-		    (caddr_t)ra->buf + done, len - done,
+		    buf + done, len - done,
 		    ra->voff, UIO_SYSSPACE, FAPPEND,
 		    RLIM64_INFINITY, CRED(), &resid);
 
@@ -1237,12 +1239,11 @@ restore_read(struct restorearg *ra, int len)
 	}
 
 	ASSERT3U(done, ==, len);
-	rv = ra->buf;
 	if (ra->byteswap)
-		fletcher_4_incremental_byteswap(rv, len, &ra->cksum);
+		fletcher_4_incremental_byteswap(buf, len, &ra->cksum);
 	else
-		fletcher_4_incremental_native(rv, len, &ra->cksum);
-	return (rv);
+		fletcher_4_incremental_native(buf, len, &ra->cksum);
+	return (buf);
 }
 
 static void
@@ -1357,7 +1358,7 @@ restore_object(struct restorearg *ra, objset_t *os, struct drr_object *drro)
 		return (SET_ERROR(EINVAL));
 
 	if (drro->drr_bonuslen) {
-		data = restore_read(ra, P2ROUNDUP(drro->drr_bonuslen, 8));
+		data = restore_read(ra, P2ROUNDUP(drro->drr_bonuslen, 8), NULL);
 		if (ra->err != 0)
 			return (ra->err);
 	}
@@ -1454,19 +1455,30 @@ restore_write(struct restorearg *ra, objset_t *os,
 	    !DMU_OT_IS_VALID(drrw->drr_type))
 		return (SET_ERROR(EINVAL));
 
-	data = restore_read(ra, drrw->drr_length);
-	if (data == NULL)
-		return (ra->err);
-
 	if (dmu_object_info(os, drrw->drr_object, NULL) != 0)
 		return (SET_ERROR(EINVAL));
 
+	dmu_buf_t *bonus;
+	if (dmu_bonus_hold(os, drrw->drr_object, FTAG, &bonus) != 0)
+		return (SET_ERROR(EINVAL));
+
+	arc_buf_t *abuf = dmu_request_arcbuf(bonus, drrw->drr_length);
+
+	data = restore_read(ra, drrw->drr_length, abuf->b_data);
+	if (data == NULL) {
+		dmu_return_arcbuf(abuf);
+		dmu_buf_rele(bonus, FTAG);
+		return (ra->err);
+	}
+
 	tx = dmu_tx_create(os);
 
 	dmu_tx_hold_write(tx, drrw->drr_object,
 	    drrw->drr_offset, drrw->drr_length);
 	err = dmu_tx_assign(tx, TXG_WAIT);
 	if (err != 0) {
+		dmu_return_arcbuf(abuf);
+		dmu_buf_rele(bonus, FTAG);
 		dmu_tx_abort(tx);
 		return (err);
 	}
@@ -1475,9 +1487,9 @@ restore_write(struct restorearg *ra, objset_t *os,
 		    DMU_OT_BYTESWAP(drrw->drr_type);
 		dmu_ot_byteswap[byteswap].ob_func(data, drrw->drr_length);
 	}
-	dmu_write(os, drrw->drr_object,
-	    drrw->drr_offset, drrw->drr_length, data, tx);
+	dmu_assign_arcbuf(bonus, drrw->drr_offset, abuf, tx);
 	dmu_tx_commit(tx);
+	dmu_buf_rele(bonus, FTAG);
 	return (0);
 }
 
@@ -1559,7 +1571,7 @@ restore_write_embedded(struct restorearg *ra, objset_t *os,
 	if (drrwnp->drr_compression >= ZIO_COMPRESS_FUNCTIONS)
 		return (EINVAL);
 
-	data = restore_read(ra, P2ROUNDUP(drrwnp->drr_psize, 8));
+	data = restore_read(ra, P2ROUNDUP(drrwnp->drr_psize, 8), NULL);
 	if (data == NULL)
 		return (ra->err);
 
@@ -1594,7 +1606,7 @@ restore_spill(struct restorearg *ra, objset_t *os, struct drr_spill *drrs)
 	    drrs->drr_length > SPA_MAXBLOCKSIZE)
 		return (SET_ERROR(EINVAL));
 
-	data = restore_read(ra, drrs->drr_length);
+	data = restore_read(ra, drrs->drr_length, NULL);
 	if (data == NULL)
 		return (ra->err);
 
@@ -1735,7 +1747,7 @@ dmu_recv_stream(dmu_recv_cookie_t *drc, vnode_t *vp, offset_t *voffp,
 	 */
 	pcksum = ra.cksum;
 	while (ra.err == 0 &&
-	    NULL != (drr = restore_read(&ra, sizeof (*drr)))) {
+	    NULL != (drr = restore_read(&ra, sizeof (*drr), NULL))) {
 		if (issig(JUSTLOOKING) && issig(FORREAL)) {
 			ra.err = SET_ERROR(EINTR);
 			goto out;