]> granicus.if.org Git - zfs/commitdiff
OpenZFS 6513 - partially filled holes lose birth time
authorPaul Dagnelie <pcd@delphix.com>
Sun, 15 May 2016 15:02:28 +0000 (08:02 -0700)
committerBrian Behlendorf <behlendorf1@llnl.gov>
Tue, 21 Jun 2016 17:55:13 +0000 (10:55 -0700)
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Boris Protopopov <bprotopopov@hotmail.com>
Approved by: Richard Lowe <richlowe@richlowe.net>a
Ported by: Boris Protopopov <bprotopopov@actifio.com>
Signed-off-by: Boris Protopopov <bprotopopov@actifio.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
OpenZFS-issue: https://www.illumos.org/issues/6513
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/8df0bcf0

If a ZFS object contains a hole at level one, and then a data block is
created at level 0 underneath that l1 block, l0 holes will be created.
However, these l0 holes do not have the birth time property set; as a
result, incremental sends will not send those holes.

Fix is to modify the dbuf_read code to fill in birth time data.

include/sys/arc.h
include/sys/arc_impl.h
include/sys/zio.h
module/zfs/arc.c
module/zfs/dbuf.c
module/zfs/dmu.c
module/zfs/dmu_objset.c
module/zfs/dnode_sync.c
module/zfs/zio.c

index 5780554b5c2224dc6aa1fe6f7a4cdd21d5bef88e..8f0f6cb55ea5dde2c042ef571ff96c6099581226 100644 (file)
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  */
 
@@ -193,9 +193,11 @@ int arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
     arc_flags_t *arc_flags, const zbookmark_phys_t *zb);
 zio_t *arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
     blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress,
-    const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
-    arc_done_func_t *done, void *private, zio_priority_t priority,
-    int zio_flags, const zbookmark_phys_t *zb);
+    const zio_prop_t *zp,
+    arc_done_func_t *ready, arc_done_func_t *child_ready,
+    arc_done_func_t *physdone, arc_done_func_t *done,
+    void *private, zio_priority_t priority, int zio_flags,
+    const zbookmark_phys_t *zb);
 
 arc_prune_t *arc_add_prune_callback(arc_prune_func_t *func, void *private);
 void arc_remove_prune_callback(arc_prune_t *p);
index a9dbfc8dd73e29dbbbff3afc0aae8d096d7d2f06..5c57c3157ae816131a1aefacad481854a73e503c 100644 (file)
@@ -101,6 +101,7 @@ typedef struct arc_write_callback arc_write_callback_t;
 struct arc_write_callback {
        void            *awcb_private;
        arc_done_func_t *awcb_ready;
+       arc_done_func_t *awcb_children_ready;
        arc_done_func_t *awcb_physdone;
        arc_done_func_t *awcb_done;
        arc_buf_t       *awcb_buf;
index 300a5f5ab77c6396d64d7f81c2b5be8a9701c9c9..d5a1494df2a5933c448754caa428b8f5e93df1da 100644 (file)
@@ -22,7 +22,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
- * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  */
 
@@ -400,7 +400,8 @@ struct zio {
        zio_transform_t *io_transform_stack;
 
        /* Callback info */
-       zio_done_func_t *io_ready;
+       zio_done_func_t *io_ready;
+       zio_done_func_t *io_children_ready;
        zio_done_func_t *io_physdone;
        zio_done_func_t *io_done;
        void            *io_private;
@@ -468,9 +469,10 @@ extern zio_t *zio_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, void *data,
 
 extern zio_t *zio_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp,
     void *data, uint64_t size, const zio_prop_t *zp,
-    zio_done_func_t *ready, zio_done_func_t *physdone, zio_done_func_t *done,
-    void *private,
-    zio_priority_t priority, enum zio_flag flags, const zbookmark_phys_t *zb);
+    zio_done_func_t *ready, zio_done_func_t *children_ready,
+    zio_done_func_t *physdone, zio_done_func_t *done,
+    void *private, zio_priority_t priority, enum zio_flag flags,
+    const zbookmark_phys_t *zb);
 
 extern zio_t *zio_rewrite(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp,
     void *data, uint64_t size, zio_done_func_t *done, void *private,
index 18e9a145d3ffafbab31fe1570b1dcf964d5e0f7b..77181b1fd68914f896842fed388e4e2b83fdda65 100644 (file)
@@ -21,7 +21,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012, Joyent, Inc. All rights reserved.
- * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
  * Copyright 2014 Nexenta Systems, Inc.  All rights reserved.
  */
@@ -4981,6 +4981,15 @@ arc_write_ready(zio_t *zio)
        hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS;
 }
 
+static void
+arc_write_children_ready(zio_t *zio)
+{
+       arc_write_callback_t *callback = zio->io_private;
+       arc_buf_t *buf = callback->awcb_buf;
+
+       callback->awcb_children_ready(zio, buf, callback->awcb_private);
+}
+
 /*
  * The SPA calls this callback for each physical write that happens on behalf
  * of a logical write.  See the comment in dbuf_write_physdone() for details.
@@ -5077,7 +5086,8 @@ arc_write_done(zio_t *zio)
 zio_t *
 arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
     blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress,
-    const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
+    const zio_prop_t *zp, arc_done_func_t *ready,
+    arc_done_func_t *children_ready, arc_done_func_t *physdone,
     arc_done_func_t *done, void *private, zio_priority_t priority,
     int zio_flags, const zbookmark_phys_t *zb)
 {
@@ -5097,13 +5107,16 @@ arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
                hdr->b_flags |= ARC_FLAG_L2COMPRESS;
        callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
        callback->awcb_ready = ready;
+       callback->awcb_children_ready = children_ready;
        callback->awcb_physdone = physdone;
        callback->awcb_done = done;
        callback->awcb_private = private;
        callback->awcb_buf = buf;
 
        zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
-           arc_write_ready, arc_write_physdone, arc_write_done, callback,
+           arc_write_ready,
+           (children_ready != NULL) ? arc_write_children_ready : NULL,
+           arc_write_physdone, arc_write_done, callback,
            priority, zio_flags, zb);
 
        return (zio);
index fd51d59a8edb6f3921ae1e36134beaf75dd2e57b..126748994d534cab4019820b22aee7a3e6703954 100644 (file)
@@ -543,13 +543,50 @@ dbuf_verify(dmu_buf_impl_t *db)
                 * If the blkptr isn't set but they have nonzero data,
                 * it had better be dirty, otherwise we'll lose that
                 * data when we evict this buffer.
+                *
+                * There is an exception to this rule for indirect blocks; in
+                * this case, if the indirect block is a hole, we fill in a few
+                * fields on each of the child blocks (importantly, birth time)
+                * to prevent hole birth times from being lost when you
+                * partially fill in a hole.
                 */
                if (db->db_dirtycnt == 0) {
-                       ASSERTV(uint64_t *buf = db->db.db_data);
-                       int i;
+                       if (db->db_level == 0) {
+                               uint64_t *buf = db->db.db_data;
+                               int i;
 
-                       for (i = 0; i < db->db.db_size >> 3; i++) {
-                               ASSERT(buf[i] == 0);
+                               for (i = 0; i < db->db.db_size >> 3; i++) {
+                                       ASSERT(buf[i] == 0);
+                               }
+                       } else {
+                               int i;
+                               blkptr_t *bps = db->db.db_data;
+                               ASSERT3U(1 << DB_DNODE(db)->dn_indblkshift, ==,
+                                   db->db.db_size);
+                               /*
+                                * We want to verify that all the blkptrs in the
+                                * indirect block are holes, but we may have
+                                * automatically set up a few fields for them.
+                                * We iterate through each blkptr and verify
+                                * they only have those fields set.
+                                */
+                               for (i = 0;
+                                   i < db->db.db_size / sizeof (blkptr_t);
+                                   i++) {
+                                       blkptr_t *bp = &bps[i];
+                                       ASSERT(ZIO_CHECKSUM_IS_ZERO(
+                                           &bp->blk_cksum));
+                                       ASSERT(
+                                           DVA_IS_EMPTY(&bp->blk_dva[0]) &&
+                                           DVA_IS_EMPTY(&bp->blk_dva[1]) &&
+                                           DVA_IS_EMPTY(&bp->blk_dva[2]));
+                                       ASSERT0(bp->blk_fill);
+                                       ASSERT0(bp->blk_pad[0]);
+                                       ASSERT0(bp->blk_pad[1]);
+                                       ASSERT(!BP_IS_EMBEDDED(bp));
+                                       ASSERT(BP_IS_HOLE(bp));
+                                       ASSERT0(bp->blk_phys_birth);
+                               }
                        }
                }
        }
@@ -718,10 +755,32 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
            BP_IS_HOLE(db->db_blkptr)))) {
                arc_buf_contents_t type = DBUF_GET_BUFC_TYPE(db);
 
-               DB_DNODE_EXIT(db);
                dbuf_set_data(db, arc_buf_alloc(db->db_objset->os_spa,
                    db->db.db_size, db, type));
                bzero(db->db.db_data, db->db.db_size);
+
+               if (db->db_blkptr != NULL && db->db_level > 0 &&
+                   BP_IS_HOLE(db->db_blkptr) &&
+                   db->db_blkptr->blk_birth != 0) {
+                       blkptr_t *bps = db->db.db_data;
+                       int i;
+                       for (i = 0; i < ((1 <<
+                           DB_DNODE(db)->dn_indblkshift) / sizeof (blkptr_t));
+                           i++) {
+                               blkptr_t *bp = &bps[i];
+                               ASSERT3U(BP_GET_LSIZE(db->db_blkptr), ==,
+                                   1 << dn->dn_indblkshift);
+                               BP_SET_LSIZE(bp,
+                                   BP_GET_LEVEL(db->db_blkptr) == 1 ?
+                                   dn->dn_datablksz :
+                                   BP_GET_LSIZE(db->db_blkptr));
+                               BP_SET_TYPE(bp, BP_GET_TYPE(db->db_blkptr));
+                               BP_SET_LEVEL(bp,
+                                   BP_GET_LEVEL(db->db_blkptr) - 1);
+                               BP_SET_BIRTH(bp, db->db_blkptr->blk_birth, 0);
+                       }
+               }
+               DB_DNODE_EXIT(db);
                db->db_state = DB_CACHED;
                mutex_exit(&db->db_mtx);
                return (0);
@@ -3094,6 +3153,45 @@ dbuf_write_ready(zio_t *zio, arc_buf_t *buf, void *vdb)
        rw_exit(&dn->dn_struct_rwlock);
 }
 
+/* ARGSUSED */
+/*
+ * This function gets called just prior to running through the compression
+ * stage of the zio pipeline. If we're an indirect block comprised of only
+ * holes, then we want this indirect to be compressed away to a hole. In
+ * order to do that we must zero out any information about the holes that
+ * this indirect points to prior to before we try to compress it.
+ */
+static void
+dbuf_write_children_ready(zio_t *zio, arc_buf_t *buf, void *vdb)
+{
+       dmu_buf_impl_t *db = vdb;
+       dnode_t *dn;
+       blkptr_t *bp;
+       uint64_t i;
+       int epbs;
+
+       ASSERT3U(db->db_level, >, 0);
+       DB_DNODE_ENTER(db);
+       dn = DB_DNODE(db);
+       epbs = dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;
+
+       /* Determine if all our children are holes */
+       for (i = 0, bp = db->db.db_data; i < 1 << epbs; i++, bp++) {
+               if (!BP_IS_HOLE(bp))
+                       break;
+       }
+
+       /*
+        * If all the children are holes, then zero them all out so that
+        * we may get compressed away.
+        */
+       if (i == 1 << epbs) {
+               /* didn't find any non-holes */
+               bzero(db->db.db_data, db->db.db_size);
+       }
+       DB_DNODE_EXIT(db);
+}
+
 /*
  * The SPA will call this callback several times for each zio - once
  * for every physical child i/o (zio->io_phys_children times).  This
@@ -3348,7 +3446,8 @@ dbuf_write(dbuf_dirty_record_t *dr, arc_buf_t *data, dmu_tx_t *tx)
 
                dr->dr_zio = zio_write(zio, os->os_spa, txg,
                    &dr->dr_bp_copy, contents, db->db.db_size, &zp,
-                   dbuf_write_override_ready, NULL, dbuf_write_override_done,
+                   dbuf_write_override_ready, NULL, NULL,
+                   dbuf_write_override_done,
                    dr, ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_MUSTSUCCEED, &zb);
                mutex_enter(&db->db_mtx);
                dr->dt.dl.dr_override_state = DR_NOT_OVERRIDDEN;
@@ -3359,14 +3458,26 @@ dbuf_write(dbuf_dirty_record_t *dr, arc_buf_t *data, dmu_tx_t *tx)
                ASSERT(zp.zp_checksum == ZIO_CHECKSUM_OFF);
                dr->dr_zio = zio_write(zio, os->os_spa, txg,
                    &dr->dr_bp_copy, NULL, db->db.db_size, &zp,
-                   dbuf_write_nofill_ready, NULL, dbuf_write_nofill_done, db,
+                   dbuf_write_nofill_ready, NULL, NULL,
+                   dbuf_write_nofill_done, db,
                    ZIO_PRIORITY_ASYNC_WRITE,
                    ZIO_FLAG_MUSTSUCCEED | ZIO_FLAG_NODATA, &zb);
        } else {
+               arc_done_func_t *children_ready_cb = NULL;
                ASSERT(arc_released(data));
+
+               /*
+                * For indirect blocks, we want to setup the children
+                * ready callback so that we can properly handle an indirect
+                * block that only contains holes.
+                */
+               if (db->db_level != 0)
+                       children_ready_cb = dbuf_write_children_ready;
+
                dr->dr_zio = arc_write(zio, os->os_spa, txg,
                    &dr->dr_bp_copy, data, DBUF_IS_L2CACHEABLE(db),
                    DBUF_IS_L2COMPRESSIBLE(db), &zp, dbuf_write_ready,
+                   children_ready_cb,
                    dbuf_write_physdone, dbuf_write_done, db,
                    ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_MUSTSUCCEED, &zb);
        }
index 7862878341833979441c3a32f72cc225e54b5072..a423264c6d0689891afad8148a4c848c28fdedc9 100644 (file)
@@ -20,8 +20,9 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  * Copyright (c) 2014, Nexenta Systems, Inc. All rights reserved.
  * Copyright (c) 2015 by Chunwei Chen. All rights reserved.
  */
@@ -1480,10 +1481,11 @@ dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sync_cb_t *done, zgd_t *zgd,
        dsa->dsa_zgd = zgd;
        dsa->dsa_tx = tx;
 
-       zio_nowait(zio_write(pio, os->os_spa, dmu_tx_get_txg(tx), zgd->zgd_bp,
-           zgd->zgd_db->db_data, zgd->zgd_db->db_size, zp,
-           dmu_sync_late_arrival_ready, NULL, dmu_sync_late_arrival_done, dsa,
-           ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL|ZIO_FLAG_FASTWRITE, zb));
+       zio_nowait(zio_write(pio, os->os_spa, dmu_tx_get_txg(tx),
+           zgd->zgd_bp, zgd->zgd_db->db_data, zgd->zgd_db->db_size,
+           zp, dmu_sync_late_arrival_ready, NULL,
+           NULL, dmu_sync_late_arrival_done, dsa, ZIO_PRIORITY_SYNC_WRITE,
+           ZIO_FLAG_CANFAIL, zb));
 
        return (0);
 }
@@ -1636,8 +1638,8 @@ dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
        zio_nowait(arc_write(pio, os->os_spa, txg,
            bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db),
            DBUF_IS_L2COMPRESSIBLE(db), &zp, dmu_sync_ready,
-           NULL, dmu_sync_done, dsa, ZIO_PRIORITY_SYNC_WRITE,
-           ZIO_FLAG_CANFAIL, &zb));
+           NULL, NULL, dmu_sync_done, dsa,
+           ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, &zb));
 
        return (0);
 }
index c8a4351858adb82adcb1bd68a549e6a7aeab30dd..9f7cf5f4b843b009b22e44caca0d940705785a44 100644 (file)
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
@@ -1110,9 +1110,9 @@ dmu_objset_sync(objset_t *os, zio_t *pio, dmu_tx_t *tx)
 
        zio = arc_write(pio, os->os_spa, tx->tx_txg,
            os->os_rootbp, os->os_phys_buf, DMU_OS_IS_L2CACHEABLE(os),
-           DMU_OS_IS_L2COMPRESSIBLE(os), &zp, dmu_objset_write_ready,
-           NULL, dmu_objset_write_done, os, ZIO_PRIORITY_ASYNC_WRITE,
-           ZIO_FLAG_MUSTSUCCEED, &zb);
+           DMU_OS_IS_L2COMPRESSIBLE(os),
+           &zp, dmu_objset_write_ready, NULL, NULL, dmu_objset_write_done,
+           os, ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_MUSTSUCCEED, &zb);
 
        /*
         * Sync special dnodes - the parent IO for the sync is the root block
index b47395a1e26a730367dafe6411d5484cdb8d10fb..66b0eef2a9f20ab43e51ef45432636264f22533f 100644 (file)
@@ -21,7 +21,7 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
  */
 
@@ -60,20 +60,14 @@ dnode_increase_indirection(dnode_t *dn, dmu_tx_t *tx)
        dprintf("os=%p obj=%llu, increase to %d\n", dn->dn_objset,
            dn->dn_object, dn->dn_phys->dn_nlevels);
 
-       /* check for existing blkptrs in the dnode */
-       for (i = 0; i < nblkptr; i++)
-               if (!BP_IS_HOLE(&dn->dn_phys->dn_blkptr[i]))
-                       break;
-       if (i != nblkptr) {
-               /* transfer dnode's block pointers to new indirect block */
-               (void) dbuf_read(db, NULL, DB_RF_MUST_SUCCEED|DB_RF_HAVESTRUCT);
-               ASSERT(db->db.db_data);
-               ASSERT(arc_released(db->db_buf));
-               ASSERT3U(sizeof (blkptr_t) * nblkptr, <=, db->db.db_size);
-               bcopy(dn->dn_phys->dn_blkptr, db->db.db_data,
-                   sizeof (blkptr_t) * nblkptr);
-               arc_buf_freeze(db->db_buf);
-       }
+       /* transfer dnode's block pointers to new indirect block */
+       (void) dbuf_read(db, NULL, DB_RF_MUST_SUCCEED|DB_RF_HAVESTRUCT);
+       ASSERT(db->db.db_data);
+       ASSERT(arc_released(db->db_buf));
+       ASSERT3U(sizeof (blkptr_t) * nblkptr, <=, db->db.db_size);
+       bcopy(dn->dn_phys->dn_blkptr, db->db.db_data,
+           sizeof (blkptr_t) * nblkptr);
+       arc_buf_freeze(db->db_buf);
 
        /* set dbuf's parent pointers to new indirect buf */
        for (i = 0; i < nblkptr; i++) {
index 4063703adf2dd576c9b5bd1bb93fb98e7eb02e30..de56a1283c0284900ac38d2c3e637fcf5e4f4f40 100644 (file)
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2011 Nexenta Systems, Inc. All rights reserved.
  */
 
@@ -737,9 +737,10 @@ zio_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
 zio_t *
 zio_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp,
     void *data, uint64_t size, const zio_prop_t *zp,
-    zio_done_func_t *ready, zio_done_func_t *physdone, zio_done_func_t *done,
-    void *private,
-    zio_priority_t priority, enum zio_flag flags, const zbookmark_phys_t *zb)
+    zio_done_func_t *ready, zio_done_func_t *children_ready,
+    zio_done_func_t *physdone, zio_done_func_t *done,
+    void *private, zio_priority_t priority, enum zio_flag flags,
+    const zbookmark_phys_t *zb)
 {
        zio_t *zio;
 
@@ -758,6 +759,7 @@ zio_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp,
            ZIO_DDT_CHILD_WRITE_PIPELINE : ZIO_WRITE_PIPELINE);
 
        zio->io_ready = ready;
+       zio->io_children_ready = children_ready;
        zio->io_physdone = physdone;
        zio->io_prop = *zp;
 
@@ -1132,6 +1134,16 @@ zio_write_bp_init(zio_t *zio)
        if (!IO_IS_ALLOCATING(zio))
                return (ZIO_PIPELINE_CONTINUE);
 
+       if (zio->io_children_ready != NULL) {
+               /*
+                * Now that all our children are ready, run the callback
+                * associated with this zio in case it wants to modify the
+                * data to be written.
+                */
+               ASSERT3U(zp->zp_level, >, 0);
+               zio->io_children_ready(zio);
+       }
+
        ASSERT(zio->io_child_type != ZIO_CHILD_DDT);
 
        if (zio->io_bp_override) {
@@ -2143,9 +2155,9 @@ zio_write_gang_block(zio_t *pio)
 
                zio_nowait(zio_write(zio, spa, txg, &gbh->zg_blkptr[g],
                    (char *)pio->io_data + (pio->io_size - resid), lsize, &zp,
-                   zio_write_gang_member_ready, NULL, NULL, &gn->gn_child[g],
-                   pio->io_priority, ZIO_GANG_CHILD_FLAGS(pio),
-                   &pio->io_bookmark));
+                   zio_write_gang_member_ready, NULL, NULL, NULL,
+                   &gn->gn_child[g], pio->io_priority,
+                   ZIO_GANG_CHILD_FLAGS(pio), &pio->io_bookmark));
        }
 
        /*
@@ -2528,7 +2540,7 @@ zio_ddt_write(zio_t *zio)
 
                dio = zio_write(zio, spa, txg, bp, zio->io_orig_data,
                    zio->io_orig_size, &czp, NULL, NULL,
-                   zio_ddt_ditto_write_done, dde, zio->io_priority,
+                   NULL, zio_ddt_ditto_write_done, dde, zio->io_priority,
                    ZIO_DDT_CHILD_FLAGS(zio), &zio->io_bookmark);
 
                zio_push_transform(dio, zio->io_data, zio->io_size, 0, NULL);
@@ -2549,7 +2561,8 @@ zio_ddt_write(zio_t *zio)
                ddt_phys_addref(ddp);
        } else {
                cio = zio_write(zio, spa, txg, bp, zio->io_orig_data,
-                   zio->io_orig_size, zp, zio_ddt_child_write_ready, NULL,
+                   zio->io_orig_size, zp,
+                   zio_ddt_child_write_ready, NULL, NULL,
                    zio_ddt_child_write_done, dde, zio->io_priority,
                    ZIO_DDT_CHILD_FLAGS(zio), &zio->io_bookmark);