svn commit: r319742 - vendor-sys/illumos/dist/uts/common/fs/zfs

[Andriy Gapon]

Author: avg
Date: Fri Jun  9 15:02:07 2017
New Revision: 319742
URL: https://svnweb.freebsd.org/changeset/base/319742

Log:
  8056 zfs send size estimate is inaccurate for some zvols
  
  illumos/illumos-gate at 0255edcc85fc0cd1dda0e49bcd52eb66c06a1b16
  https://github.com/illumos/illumos-gate/commit/0255edcc85fc0cd1dda0e49bcd52eb66c06a1b16
  
  https://www.illumos.org/issues/8056
    The send size estimate for a zvol can be too low, if the size of the record
    headers (dmu_replay_record_t's) is a significant portion of the size.
    This is typically the case when the data is highly compressible, especially
    with embedded blocks.
    The problem is that dmu_adjust_send_estimate_for_indirects() assumes that
    blocks are the size of the "recordsize" property (128KB).
    However, for zvols, the blocks are the size of the "volblocksize" property
    (8KB). Therefore, we estimate that there will be 16x less record headers than
    there really will be.
  
  Reviewed by: Matthew Ahrens <mahrens at delphix.com>
  Reviewed by: Pavel Zakharov <pavel.zakharov at delphix.com>
  Approved by: Robert Mustacchi <rm at joyent.com>
  Author: Paul Dagnelie <pcd at delphix.com>

Modified:
  vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_send.c

Modified: vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_send.c
==============================================================================
--- vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_send.c	Fri Jun  9 15:01:18 2017	(r319741)
+++ vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_send.c	Fri Jun  9 15:02:07 2017	(r319742)
@@ -1102,10 +1102,17 @@ dmu_adjust_send_estimate_for_indirects(dsl_dataset_t *
 	 */
 	uint64_t recordsize;
 	uint64_t record_count;
+	objset_t *os;
+	VERIFY0(dmu_objset_from_ds(ds, &os));
 
 	/* Assume all (uncompressed) blocks are recordsize. */
-	err = dsl_prop_get_int_ds(ds, zfs_prop_to_name(ZFS_PROP_RECORDSIZE),
-	    &recordsize);
+	if (os->os_phys->os_type == DMU_OST_ZVOL) {
+		err = dsl_prop_get_int_ds(ds,
+		    zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE), &recordsize);
+	} else {
+		err = dsl_prop_get_int_ds(ds,
+		    zfs_prop_to_name(ZFS_PROP_RECORDSIZE), &recordsize);
+	}
 	if (err != 0)
 		return (err);
 	record_count = uncompressed / recordsize;
@@ -1174,6 +1181,10 @@ dmu_send_estimate(dsl_dataset_t *ds, dsl_dataset_t *fr
 
 	err = dmu_adjust_send_estimate_for_indirects(ds, uncomp, comp,
 	    stream_compressed, sizep);
+	/*
+	 * Add the size of the BEGIN and END records to the estimate.
+	 */
+	*sizep += 2 * sizeof (dmu_replay_record_t);
 	return (err);
 }