Illumos 5695 - dmu_sync'ed holes do not retain birth time

5695 dmu_sync'ed holes do not retain birth time
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Bayard Bell <buffer.g.overflow@gmail.com>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://www.illumos.org/issues/5695
  illumos/illumos-gate@70163ac

Ported-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3229

Author: Prakash Surya

cmd/zdb/zdb.c

@@ -1115,7 +1115,9 @@ snprintf_blkptr_compact(char *blkbuf, size_t buflen, const blkptr_t *bp)
 
 	if (BP_IS_HOLE(bp)) {
 		(void) snprintf(blkbuf + strlen(blkbuf),
-		    buflen - strlen(blkbuf), "B=%llu",
+		    buflen - strlen(blkbuf),
+		    "%llxL B=%llu",
+		    (u_longlong_t)BP_GET_LSIZE(bp),
 		    (u_longlong_t)bp->blk_birth);
 	} else {
 		(void) snprintf(blkbuf + strlen(blkbuf),

include/sys/spa.h

@@ -501,12 +501,13 @@ _NOTE(CONSTCOND) } while (0)
 	if (bp == NULL) {						\
 		len += func(buf + len, size - len, "<NULL>");		\
 	} else if (BP_IS_HOLE(bp)) {					\
-		len += func(buf + len, size - len, "<hole>");		\
-		if (bp->blk_birth > 0) {				\
-			len += func(buf + len, size - len,		\
-			    " birth=%lluL",				\
-			    (u_longlong_t)bp->blk_birth);		\
-		}							\
+		len += func(buf + len, size - len,			\
+		    "HOLE [L%llu %s] "					\
+		    "size=%llxL birth=%lluL",				\
+		    (u_longlong_t)BP_GET_LEVEL(bp),			\
+		    type,						\
+		    (u_longlong_t)BP_GET_LSIZE(bp),			\
+		    (u_longlong_t)bp->blk_birth);			\
 	} else if (BP_IS_EMBEDDED(bp)) {				\
 		len = func(buf + len, size - len,			\
 		    "EMBEDDED [L%llu %s] et=%u %s "			\

module/zfs/dmu.c

@@ -1472,7 +1472,19 @@ dmu_sync_done(zio_t *zio, arc_buf_t *buf, void *varg)
 		dr->dt.dl.dr_overridden_by = *zio->io_bp;
 		dr->dt.dl.dr_override_state = DR_OVERRIDDEN;
 		dr->dt.dl.dr_copies = zio->io_prop.zp_copies;
-		if (BP_IS_HOLE(&dr->dt.dl.dr_overridden_by))
+
+		/*
+		 * Old style holes are filled with all zeros, whereas
+		 * new-style holes maintain their lsize, type, level,
+		 * and birth time (see zio_write_compress). While we
+		 * need to reset the BP_SET_LSIZE() call that happened
+		 * in dmu_sync_ready for old style holes, we do *not*
+		 * want to wipe out the information contained in new
+		 * style holes. Thus, only zero out the block pointer if
+		 * it's an old style hole.
+		 */
+		if (BP_IS_HOLE(&dr->dt.dl.dr_overridden_by) &&
+		    dr->dt.dl.dr_overridden_by.blk_birth == 0)
 			BP_ZERO(&dr->dt.dl.dr_overridden_by);
 	} else {
 		dr->dt.dl.dr_override_state = DR_NOT_OVERRIDDEN;