]> git.proxmox.com Git - mirror_zfs.git/blobdiff - module/zfs/dmu_traverse.c
Fix hung z_zvol tasks during 'zfs receive'
[mirror_zfs.git] / module / zfs / dmu_traverse.c
index 51240147077310639c99b3a7072a334713ef04a9..f63903ef649dc82960c263b164484d0b170c9d28 100644 (file)
@@ -19,8 +19,8 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
- * Use is subject to license terms.
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
 #include <sys/dsl_pool.h>
 #include <sys/dnode.h>
 #include <sys/spa.h>
+#include <sys/spa_impl.h>
 #include <sys/zio.h>
 #include <sys/dmu_impl.h>
+#include <sys/sa.h>
+#include <sys/sa_impl.h>
 #include <sys/callb.h>
+#include <sys/zfeature.h>
 
-#define        SET_BOOKMARK(zb, objset, object, level, blkid)  \
-{                                                       \
-       (zb)->zb_objset = objset;                       \
-       (zb)->zb_object = object;                       \
-       (zb)->zb_level = level;                         \
-       (zb)->zb_blkid = blkid;                         \
-}
+int32_t zfs_pd_bytes_max = 50 * 1024 * 1024;   /* 50MB */
+int32_t send_holes_without_birth_time = 1;
 
-struct prefetch_data {
+typedef struct prefetch_data {
        kmutex_t pd_mtx;
        kcondvar_t pd_cv;
-       int pd_blks_max;
-       int pd_blks_fetched;
+       int32_t pd_bytes_fetched;
        int pd_flags;
        boolean_t pd_cancel;
        boolean_t pd_exited;
-};
+       zbookmark_phys_t pd_resume;
+} prefetch_data_t;
 
-struct traverse_data {
+typedef struct traverse_data {
        spa_t *td_spa;
        uint64_t td_objset;
        blkptr_t *td_rootbp;
        uint64_t td_min_txg;
+       zbookmark_phys_t *td_resume;
        int td_flags;
-       struct prefetch_data *td_pfd;
+       prefetch_data_t *td_pfd;
+       boolean_t td_paused;
+       uint64_t td_hole_birth_enabled_txg;
        blkptr_cb_t *td_func;
        void *td_arg;
-};
+       boolean_t td_realloc_possible;
+} traverse_data_t;
 
-/* ARGSUSED */
-static void
+static int traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp,
+    uint64_t objset, uint64_t object);
+static void prefetch_dnode_metadata(traverse_data_t *td, const dnode_phys_t *,
+    uint64_t objset, uint64_t object);
+
+static int
 traverse_zil_block(zilog_t *zilog, blkptr_t *bp, void *arg, uint64_t claim_txg)
 {
-       struct traverse_data *td = arg;
-       zbookmark_t zb;
+       traverse_data_t *td = arg;
+       zbookmark_phys_t zb;
 
-       if (bp->blk_birth == 0)
-               return;
+       if (BP_IS_HOLE(bp))
+               return (0);
 
        if (claim_txg == 0 && bp->blk_birth >= spa_first_txg(td->td_spa))
-               return;
+               return (0);
+
+       SET_BOOKMARK(&zb, td->td_objset, ZB_ZIL_OBJECT, ZB_ZIL_LEVEL,
+           bp->blk_cksum.zc_word[ZIL_ZC_SEQ]);
 
-       zb.zb_objset = td->td_objset;
-       zb.zb_object = 0;
-       zb.zb_level = -1;
-       zb.zb_blkid = bp->blk_cksum.zc_word[ZIL_ZC_SEQ];
-       VERIFY(0 == td->td_func(td->td_spa, bp, &zb, NULL, td->td_arg));
+       (void) td->td_func(td->td_spa, zilog, bp, &zb, NULL, td->td_arg);
+
+       return (0);
 }
 
-/* ARGSUSED */
-static void
+static int
 traverse_zil_record(zilog_t *zilog, lr_t *lrc, void *arg, uint64_t claim_txg)
 {
-       struct traverse_data *td = arg;
+       traverse_data_t *td = arg;
 
        if (lrc->lrc_txtype == TX_WRITE) {
                lr_write_t *lr = (lr_write_t *)lrc;
                blkptr_t *bp = &lr->lr_blkptr;
-               zbookmark_t zb;
+               zbookmark_phys_t zb;
 
-               if (bp->blk_birth == 0)
-                       return;
+               if (BP_IS_HOLE(bp))
+                       return (0);
 
                if (claim_txg == 0 || bp->blk_birth < claim_txg)
-                       return;
+                       return (0);
 
-               zb.zb_objset = td->td_objset;
-               zb.zb_object = lr->lr_foid;
-               zb.zb_level = BP_GET_LEVEL(bp);
-               zb.zb_blkid = lr->lr_offset / BP_GET_LSIZE(bp);
-               VERIFY(0 == td->td_func(td->td_spa, bp, &zb, NULL, td->td_arg));
+               SET_BOOKMARK(&zb, td->td_objset, lr->lr_foid,
+                   ZB_ZIL_LEVEL, lr->lr_offset / BP_GET_LSIZE(bp));
+
+               (void) td->td_func(td->td_spa, zilog, bp, &zb, NULL,
+                   td->td_arg);
        }
+       return (0);
 }
 
 static void
-traverse_zil(struct traverse_data *td, zil_header_t *zh)
+traverse_zil(traverse_data_t *td, zil_header_t *zh)
 {
        uint64_t claim_txg = zh->zh_claim_txg;
        zilog_t *zilog;
 
        /*
         * We only want to visit blocks that have been claimed but not yet
-        * replayed (or, in read-only mode, blocks that *would* be claimed).
+        * replayed; plus, in read-only mode, blocks that are already stable.
         */
-       if (claim_txg == 0 && (spa_mode & FWRITE))
+       if (claim_txg == 0 && spa_writeable(td->td_spa))
                return;
 
        zilog = zil_alloc(spa_get_dsl(td->td_spa)->dp_meta_objset, zh);
@@ -130,152 +138,389 @@ traverse_zil(struct traverse_data *td, zil_header_t *zh)
        zil_free(zilog);
 }
 
+typedef enum resume_skip {
+       RESUME_SKIP_ALL,
+       RESUME_SKIP_NONE,
+       RESUME_SKIP_CHILDREN
+} resume_skip_t;
+
+/*
+ * Returns RESUME_SKIP_ALL if td indicates that we are resuming a traversal and
+ * the block indicated by zb does not need to be visited at all. Returns
+ * RESUME_SKIP_CHILDREN if we are resuming a post traversal and we reach the
+ * resume point. This indicates that this block should be visited but not its
+ * children (since they must have been visited in a previous traversal).
+ * Otherwise returns RESUME_SKIP_NONE.
+ */
+static resume_skip_t
+resume_skip_check(traverse_data_t *td, const dnode_phys_t *dnp,
+    const zbookmark_phys_t *zb)
+{
+       if (td->td_resume != NULL && !ZB_IS_ZERO(td->td_resume)) {
+               /*
+                * If we already visited this bp & everything below,
+                * don't bother doing it again.
+                */
+               if (zbookmark_subtree_completed(dnp, zb, td->td_resume))
+                       return (RESUME_SKIP_ALL);
+
+               /*
+                * If we found the block we're trying to resume from, zero
+                * the bookmark out to indicate that we have resumed.
+                */
+               if (bcmp(zb, td->td_resume, sizeof (*zb)) == 0) {
+                       bzero(td->td_resume, sizeof (*zb));
+                       if (td->td_flags & TRAVERSE_POST)
+                               return (RESUME_SKIP_CHILDREN);
+               }
+       }
+       return (RESUME_SKIP_NONE);
+}
+
+static void
+traverse_prefetch_metadata(traverse_data_t *td,
+    const blkptr_t *bp, const zbookmark_phys_t *zb)
+{
+       arc_flags_t flags = ARC_FLAG_NOWAIT | ARC_FLAG_PREFETCH;
+
+       if (!(td->td_flags & TRAVERSE_PREFETCH_METADATA))
+               return;
+       /*
+        * If we are in the process of resuming, don't prefetch, because
+        * some children will not be needed (and in fact may have already
+        * been freed).
+        */
+       if (td->td_resume != NULL && !ZB_IS_ZERO(td->td_resume))
+               return;
+       if (BP_IS_HOLE(bp) || bp->blk_birth <= td->td_min_txg)
+               return;
+       if (BP_GET_LEVEL(bp) == 0 && BP_GET_TYPE(bp) != DMU_OT_DNODE)
+               return;
+
+       (void) arc_read(NULL, td->td_spa, bp, NULL, NULL,
+           ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
+}
+
+static boolean_t
+prefetch_needed(prefetch_data_t *pfd, const blkptr_t *bp)
+{
+       ASSERT(pfd->pd_flags & TRAVERSE_PREFETCH_DATA);
+       if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp) ||
+           BP_GET_TYPE(bp) == DMU_OT_INTENT_LOG)
+               return (B_FALSE);
+       return (B_TRUE);
+}
+
 static int
-traverse_visitbp(struct traverse_data *td, const dnode_phys_t *dnp,
-    arc_buf_t *pbuf, blkptr_t *bp, const zbookmark_t *zb)
+traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
+    const blkptr_t *bp, const zbookmark_phys_t *zb)
 {
-       zbookmark_t czb;
        int err = 0;
        arc_buf_t *buf = NULL;
-       struct prefetch_data *pd = td->td_pfd;
+       prefetch_data_t *pd = td->td_pfd;
 
-       if (bp->blk_birth == 0) {
-               err = td->td_func(td->td_spa, NULL, zb, dnp, td->td_arg);
-               return (err);
+       switch (resume_skip_check(td, dnp, zb)) {
+       case RESUME_SKIP_ALL:
+               return (0);
+       case RESUME_SKIP_CHILDREN:
+               goto post;
+       case RESUME_SKIP_NONE:
+               break;
+       default:
+               ASSERT(0);
        }
 
-       if (bp->blk_birth <= td->td_min_txg)
+       if (bp->blk_birth == 0) {
+               /*
+                * Since this block has a birth time of 0 it must be one of
+                * two things: a hole created before the
+                * SPA_FEATURE_HOLE_BIRTH feature was enabled, or a hole
+                * which has always been a hole in an object.
+                *
+                * If a file is written sparsely, then the unwritten parts of
+                * the file were "always holes" -- that is, they have been
+                * holes since this object was allocated.  However, we (and
+                * our callers) can not necessarily tell when an object was
+                * allocated.  Therefore, if it's possible that this object
+                * was freed and then its object number reused, we need to
+                * visit all the holes with birth==0.
+                *
+                * If it isn't possible that the object number was reused,
+                * then if SPA_FEATURE_HOLE_BIRTH was enabled before we wrote
+                * all the blocks we will visit as part of this traversal,
+                * then this hole must have always existed, so we can skip
+                * it.  We visit blocks born after (exclusive) td_min_txg.
+                *
+                * Note that the meta-dnode cannot be reallocated.
+                */
+               if (!send_holes_without_birth_time &&
+                   (!td->td_realloc_possible ||
+                   zb->zb_object == DMU_META_DNODE_OBJECT) &&
+                   td->td_hole_birth_enabled_txg <= td->td_min_txg)
+                       return (0);
+       } else if (bp->blk_birth <= td->td_min_txg) {
                return (0);
+       }
 
-       if (pd && !pd->pd_exited &&
-           ((pd->pd_flags & TRAVERSE_PREFETCH_DATA) ||
-           BP_GET_TYPE(bp) == DMU_OT_DNODE || BP_GET_LEVEL(bp) > 0)) {
+       if (pd != NULL && !pd->pd_exited && prefetch_needed(pd, bp)) {
+               uint64_t size = BP_GET_LSIZE(bp);
                mutex_enter(&pd->pd_mtx);
-               ASSERT(pd->pd_blks_fetched >= 0);
-               while (pd->pd_blks_fetched == 0 && !pd->pd_exited)
-                       cv_wait(&pd->pd_cv, &pd->pd_mtx);
-               pd->pd_blks_fetched--;
+               ASSERT(pd->pd_bytes_fetched >= 0);
+               while (pd->pd_bytes_fetched < size && !pd->pd_exited)
+                       cv_wait_sig(&pd->pd_cv, &pd->pd_mtx);
+               pd->pd_bytes_fetched -= size;
                cv_broadcast(&pd->pd_cv);
                mutex_exit(&pd->pd_mtx);
        }
 
+       if (BP_IS_HOLE(bp)) {
+               err = td->td_func(td->td_spa, NULL, bp, zb, dnp, td->td_arg);
+               if (err != 0)
+                       goto post;
+               return (0);
+       }
+
        if (td->td_flags & TRAVERSE_PRE) {
-               err = td->td_func(td->td_spa, bp, zb, dnp, td->td_arg);
-               if (err)
-                       return (err);
+               err = td->td_func(td->td_spa, NULL, bp, zb, dnp,
+                   td->td_arg);
+               if (err == TRAVERSE_VISIT_NO_CHILDREN)
+                       return (0);
+               if (err != 0)
+                       goto post;
        }
 
        if (BP_GET_LEVEL(bp) > 0) {
-               uint32_t flags = ARC_WAIT;
-               int i;
-               blkptr_t *cbp;
-               int epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT;
+               uint32_t flags = ARC_FLAG_WAIT;
+               int32_t i;
+               int32_t epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT;
+               zbookmark_phys_t *czb;
 
-               err = arc_read(NULL, td->td_spa, bp, pbuf,
-                   arc_getbuf_func, &buf,
+               err = arc_read(NULL, td->td_spa, bp, arc_getbuf_func, &buf,
                    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
-               if (err)
-                       return (err);
+               if (err != 0)
+                       goto post;
+
+               czb = kmem_alloc(sizeof (zbookmark_phys_t), KM_SLEEP);
+
+               for (i = 0; i < epb; i++) {
+                       SET_BOOKMARK(czb, zb->zb_objset, zb->zb_object,
+                           zb->zb_level - 1,
+                           zb->zb_blkid * epb + i);
+                       traverse_prefetch_metadata(td,
+                           &((blkptr_t *)buf->b_data)[i], czb);
+               }
 
                /* recursively visitbp() blocks below this */
-               cbp = buf->b_data;
-               for (i = 0; i < epb; i++, cbp++) {
-                       SET_BOOKMARK(&czb, zb->zb_objset, zb->zb_object,
+               for (i = 0; i < epb; i++) {
+                       SET_BOOKMARK(czb, zb->zb_objset, zb->zb_object,
                            zb->zb_level - 1,
                            zb->zb_blkid * epb + i);
-                       err = traverse_visitbp(td, dnp, buf, cbp, &czb);
-                       if (err)
+                       err = traverse_visitbp(td, dnp,
+                           &((blkptr_t *)buf->b_data)[i], czb);
+                       if (err != 0)
                                break;
                }
+
+               kmem_free(czb, sizeof (zbookmark_phys_t));
+
        } else if (BP_GET_TYPE(bp) == DMU_OT_DNODE) {
-               uint32_t flags = ARC_WAIT;
-               int i, j;
-               int epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;
+               uint32_t flags = ARC_FLAG_WAIT;
+               int32_t i;
+               int32_t epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;
+               dnode_phys_t *child_dnp;
 
-               err = arc_read(NULL, td->td_spa, bp, pbuf,
-                   arc_getbuf_func, &buf,
+               err = arc_read(NULL, td->td_spa, bp, arc_getbuf_func, &buf,
                    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
-               if (err)
-                       return (err);
+               if (err != 0)
+                       goto post;
+               child_dnp = buf->b_data;
+
+               for (i = 0; i < epb; i += child_dnp[i].dn_extra_slots + 1) {
+                       prefetch_dnode_metadata(td, &child_dnp[i],
+                           zb->zb_objset, zb->zb_blkid * epb + i);
+               }
 
                /* recursively visitbp() blocks below this */
-               dnp = buf->b_data;
-               for (i = 0; i < epb && err == 0; i++, dnp++) {
-                       for (j = 0; j < dnp->dn_nblkptr; j++) {
-                               SET_BOOKMARK(&czb, zb->zb_objset,
-                                   zb->zb_blkid * epb + i,
-                                   dnp->dn_nlevels - 1, j);
-                               err = traverse_visitbp(td, dnp, buf,
-                                   (blkptr_t *)&dnp->dn_blkptr[j], &czb);
-                               if (err)
-                                       break;
-                       }
+               for (i = 0; i < epb; i += child_dnp[i].dn_extra_slots + 1) {
+                       err = traverse_dnode(td, &child_dnp[i],
+                           zb->zb_objset, zb->zb_blkid * epb + i);
+                       if (err != 0)
+                               break;
                }
        } else if (BP_GET_TYPE(bp) == DMU_OT_OBJSET) {
-               uint32_t flags = ARC_WAIT;
+               arc_flags_t flags = ARC_FLAG_WAIT;
                objset_phys_t *osp;
-               int j;
 
-               err = arc_read_nolock(NULL, td->td_spa, bp,
-                   arc_getbuf_func, &buf,
+               err = arc_read(NULL, td->td_spa, bp, arc_getbuf_func, &buf,
                    ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_CANFAIL, &flags, zb);
-               if (err)
-                       return (err);
+               if (err != 0)
+                       goto post;
 
                osp = buf->b_data;
+               prefetch_dnode_metadata(td, &osp->os_meta_dnode, zb->zb_objset,
+                   DMU_META_DNODE_OBJECT);
                /*
-                * traverse_zil is just here for zdb's leak checking.
-                * For other consumers, there will be no ZIL blocks.
+                * See the block comment above for the goal of this variable.
+                * If the maxblkid of the meta-dnode is 0, then we know that
+                * we've never had more than DNODES_PER_BLOCK objects in the
+                * dataset, which means we can't have reused any object ids.
                 */
-               traverse_zil(td, &osp->os_zil_header);
-
-               for (j = 0; j < osp->os_meta_dnode.dn_nblkptr; j++) {
-                       SET_BOOKMARK(&czb, zb->zb_objset, 0,
-                           osp->os_meta_dnode.dn_nlevels - 1, j);
-                       err = traverse_visitbp(td, &osp->os_meta_dnode, buf,
-                           (blkptr_t *)&osp->os_meta_dnode.dn_blkptr[j],
-                           &czb);
-                       if (err)
-                               break;
+               if (osp->os_meta_dnode.dn_maxblkid == 0)
+                       td->td_realloc_possible = B_FALSE;
+
+               if (arc_buf_size(buf) >= sizeof (objset_phys_t)) {
+                       prefetch_dnode_metadata(td, &osp->os_groupused_dnode,
+                           zb->zb_objset, DMU_GROUPUSED_OBJECT);
+                       prefetch_dnode_metadata(td, &osp->os_userused_dnode,
+                           zb->zb_objset, DMU_USERUSED_OBJECT);
+               }
+
+               err = traverse_dnode(td, &osp->os_meta_dnode, zb->zb_objset,
+                   DMU_META_DNODE_OBJECT);
+               if (err == 0 && arc_buf_size(buf) >= sizeof (objset_phys_t)) {
+                       err = traverse_dnode(td, &osp->os_groupused_dnode,
+                           zb->zb_objset, DMU_GROUPUSED_OBJECT);
+               }
+               if (err == 0 && arc_buf_size(buf) >= sizeof (objset_phys_t)) {
+                       err = traverse_dnode(td, &osp->os_userused_dnode,
+                           zb->zb_objset, DMU_USERUSED_OBJECT);
                }
        }
 
        if (buf)
-               (void) arc_buf_remove_ref(buf, &buf);
+               arc_buf_destroy(buf, &buf);
 
+post:
        if (err == 0 && (td->td_flags & TRAVERSE_POST))
-               err = td->td_func(td->td_spa, bp, zb, dnp, td->td_arg);
+               err = td->td_func(td->td_spa, NULL, bp, zb, dnp, td->td_arg);
 
+       if ((td->td_flags & TRAVERSE_HARD) && (err == EIO || err == ECKSUM)) {
+               /*
+                * Ignore this disk error as requested by the HARD flag,
+                * and continue traversal.
+                */
+               err = 0;
+       }
+
+       /*
+        * If we are stopping here, set td_resume.
+        */
+       if (td->td_resume != NULL && err != 0 && !td->td_paused) {
+               td->td_resume->zb_objset = zb->zb_objset;
+               td->td_resume->zb_object = zb->zb_object;
+               td->td_resume->zb_level = 0;
+               /*
+                * If we have stopped on an indirect block (e.g. due to
+                * i/o error), we have not visited anything below it.
+                * Set the bookmark to the first level-0 block that we need
+                * to visit.  This way, the resuming code does not need to
+                * deal with resuming from indirect blocks.
+                *
+                * Note, if zb_level <= 0, dnp may be NULL, so we don't want
+                * to dereference it.
+                */
+               td->td_resume->zb_blkid = zb->zb_blkid;
+               if (zb->zb_level > 0) {
+                       td->td_resume->zb_blkid <<= zb->zb_level *
+                           (dnp->dn_indblkshift - SPA_BLKPTRSHIFT);
+               }
+               td->td_paused = B_TRUE;
+       }
+
+       return (err);
+}
+
+static void
+prefetch_dnode_metadata(traverse_data_t *td, const dnode_phys_t *dnp,
+    uint64_t objset, uint64_t object)
+{
+       int j;
+       zbookmark_phys_t czb;
+
+       for (j = 0; j < dnp->dn_nblkptr; j++) {
+               SET_BOOKMARK(&czb, objset, object, dnp->dn_nlevels - 1, j);
+               traverse_prefetch_metadata(td, &dnp->dn_blkptr[j], &czb);
+       }
+
+       if (dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR) {
+               SET_BOOKMARK(&czb, objset, object, 0, DMU_SPILL_BLKID);
+               traverse_prefetch_metadata(td, DN_SPILL_BLKPTR(dnp), &czb);
+       }
+}
+
+static int
+traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp,
+    uint64_t objset, uint64_t object)
+{
+       int j, err = 0;
+       zbookmark_phys_t czb;
+
+       if (object != DMU_META_DNODE_OBJECT && td->td_resume != NULL &&
+           object < td->td_resume->zb_object)
+               return (0);
+
+       if (td->td_flags & TRAVERSE_PRE) {
+               SET_BOOKMARK(&czb, objset, object, ZB_DNODE_LEVEL,
+                   ZB_DNODE_BLKID);
+               err = td->td_func(td->td_spa, NULL, NULL, &czb, dnp,
+                   td->td_arg);
+               if (err == TRAVERSE_VISIT_NO_CHILDREN)
+                       return (0);
+               if (err != 0)
+                       return (err);
+       }
+
+       for (j = 0; j < dnp->dn_nblkptr; j++) {
+               SET_BOOKMARK(&czb, objset, object, dnp->dn_nlevels - 1, j);
+               err = traverse_visitbp(td, dnp, &dnp->dn_blkptr[j], &czb);
+               if (err != 0)
+                       break;
+       }
+
+       if (err == 0 && (dnp->dn_flags & DNODE_FLAG_SPILL_BLKPTR)) {
+               SET_BOOKMARK(&czb, objset, object, 0, DMU_SPILL_BLKID);
+               err = traverse_visitbp(td, dnp, DN_SPILL_BLKPTR(dnp), &czb);
+       }
+
+       if (err == 0 && (td->td_flags & TRAVERSE_POST)) {
+               SET_BOOKMARK(&czb, objset, object, ZB_DNODE_LEVEL,
+                   ZB_DNODE_BLKID);
+               err = td->td_func(td->td_spa, NULL, NULL, &czb, dnp,
+                   td->td_arg);
+               if (err == TRAVERSE_VISIT_NO_CHILDREN)
+                       return (0);
+               if (err != 0)
+                       return (err);
+       }
        return (err);
 }
 
 /* ARGSUSED */
 static int
-traverse_prefetcher(spa_t *spa, blkptr_t *bp, const zbookmark_t *zb,
-    const dnode_phys_t *dnp, void *arg)
+traverse_prefetcher(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
+    const zbookmark_phys_t *zb, const dnode_phys_t *dnp, void *arg)
 {
-       struct prefetch_data *pfd = arg;
-       uint32_t aflags = ARC_NOWAIT | ARC_PREFETCH;
+       prefetch_data_t *pfd = arg;
+       arc_flags_t aflags = ARC_FLAG_NOWAIT | ARC_FLAG_PREFETCH;
 
-       ASSERT(pfd->pd_blks_fetched >= 0);
+       ASSERT(pfd->pd_bytes_fetched >= 0);
+       if (bp == NULL)
+               return (0);
        if (pfd->pd_cancel)
-               return (EINTR);
+               return (SET_ERROR(EINTR));
 
-       if (bp == NULL || !((pfd->pd_flags & TRAVERSE_PREFETCH_DATA) ||
-           BP_GET_TYPE(bp) == DMU_OT_DNODE || BP_GET_LEVEL(bp) > 0))
+       if (!prefetch_needed(pfd, bp))
                return (0);
 
        mutex_enter(&pfd->pd_mtx);
-       while (!pfd->pd_cancel && pfd->pd_blks_fetched >= pfd->pd_blks_max)
-               cv_wait(&pfd->pd_cv, &pfd->pd_mtx);
-       pfd->pd_blks_fetched++;
+       while (!pfd->pd_cancel && pfd->pd_bytes_fetched >= zfs_pd_bytes_max)
+               cv_wait_sig(&pfd->pd_cv, &pfd->pd_mtx);
+       pfd->pd_bytes_fetched += BP_GET_LSIZE(bp);
        cv_broadcast(&pfd->pd_cv);
        mutex_exit(&pfd->pd_mtx);
 
-       (void) arc_read_nolock(NULL, spa, bp, NULL, NULL,
-           ZIO_PRIORITY_ASYNC_READ,
-           ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE,
-           &aflags, zb);
+       (void) arc_read(NULL, spa, bp, NULL, NULL, ZIO_PRIORITY_ASYNC_READ,
+           ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE, &aflags, zb);
 
        return (0);
 }
@@ -283,21 +528,25 @@ traverse_prefetcher(spa_t *spa, blkptr_t *bp, const zbookmark_t *zb,
 static void
 traverse_prefetch_thread(void *arg)
 {
-       struct traverse_data *td_main = arg;
-       struct traverse_data td = *td_main;
-       zbookmark_t czb;
+       traverse_data_t *td_main = arg;
+       traverse_data_t td = *td_main;
+       zbookmark_phys_t czb;
+       fstrans_cookie_t cookie = spl_fstrans_mark();
 
        td.td_func = traverse_prefetcher;
        td.td_arg = td_main->td_pfd;
        td.td_pfd = NULL;
+       td.td_resume = &td_main->td_pfd->pd_resume;
 
-       SET_BOOKMARK(&czb, td.td_objset, 0, -1, 0);
-       (void) traverse_visitbp(&td, NULL, NULL, td.td_rootbp, &czb);
+       SET_BOOKMARK(&czb, td.td_objset,
+           ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
+       (void) traverse_visitbp(&td, NULL, td.td_rootbp, &czb);
 
        mutex_enter(&td_main->td_pfd->pd_mtx);
        td_main->td_pfd->pd_exited = B_TRUE;
        cv_broadcast(&td_main->td_pfd->pd_cv);
        mutex_exit(&td_main->td_pfd->pd_mtx);
+       spl_fstrans_unmark(cookie);
 }
 
 /*
@@ -305,45 +554,95 @@ traverse_prefetch_thread(void *arg)
  * in syncing context).
  */
 static int
-traverse_impl(spa_t *spa, uint64_t objset, blkptr_t *rootbp,
-    uint64_t txg_start, int flags, blkptr_cb_t func, void *arg)
+traverse_impl(spa_t *spa, dsl_dataset_t *ds, uint64_t objset, blkptr_t *rootbp,
+    uint64_t txg_start, zbookmark_phys_t *resume, int flags,
+    blkptr_cb_t func, void *arg)
 {
-       struct traverse_data td;
-       struct prefetch_data pd = { 0 };
-       zbookmark_czb;
+       traverse_data_t *td;
+       prefetch_data_t *pd;
+       zbookmark_phys_t *czb;
        int err;
 
-       td.td_spa = spa;
-       td.td_objset = objset;
-       td.td_rootbp = rootbp;
-       td.td_min_txg = txg_start;
-       td.td_func = func;
-       td.td_arg = arg;
-       td.td_pfd = &pd;
-       td.td_flags = flags;
-
-       pd.pd_blks_max = 100;
-       pd.pd_flags = flags;
-       mutex_init(&pd.pd_mtx, NULL, MUTEX_DEFAULT, NULL);
-       cv_init(&pd.pd_cv, NULL, CV_DEFAULT, NULL);
-
-       if (!(flags & TRAVERSE_PREFETCH) ||
-           0 == taskq_dispatch(system_taskq, traverse_prefetch_thread,
-           &td, TQ_NOQUEUE))
-               pd.pd_exited = B_TRUE;
-
-       SET_BOOKMARK(&czb, objset, 0, -1, 0);
-       err = traverse_visitbp(&td, NULL, NULL, rootbp, &czb);
-
-       mutex_enter(&pd.pd_mtx);
-       pd.pd_cancel = B_TRUE;
-       cv_broadcast(&pd.pd_cv);
-       while (!pd.pd_exited)
-               cv_wait(&pd.pd_cv, &pd.pd_mtx);
-       mutex_exit(&pd.pd_mtx);
-
-       mutex_destroy(&pd.pd_mtx);
-       cv_destroy(&pd.pd_cv);
+       ASSERT(ds == NULL || objset == ds->ds_object);
+       ASSERT(!(flags & TRAVERSE_PRE) || !(flags & TRAVERSE_POST));
+
+       td = kmem_alloc(sizeof (traverse_data_t), KM_SLEEP);
+       pd = kmem_zalloc(sizeof (prefetch_data_t), KM_SLEEP);
+       czb = kmem_alloc(sizeof (zbookmark_phys_t), KM_SLEEP);
+
+       td->td_spa = spa;
+       td->td_objset = objset;
+       td->td_rootbp = rootbp;
+       td->td_min_txg = txg_start;
+       td->td_resume = resume;
+       td->td_func = func;
+       td->td_arg = arg;
+       td->td_pfd = pd;
+       td->td_flags = flags;
+       td->td_paused = B_FALSE;
+       td->td_realloc_possible = (txg_start == 0 ? B_FALSE : B_TRUE);
+
+       if (spa_feature_is_active(spa, SPA_FEATURE_HOLE_BIRTH)) {
+               VERIFY(spa_feature_enabled_txg(spa,
+                   SPA_FEATURE_HOLE_BIRTH, &td->td_hole_birth_enabled_txg));
+       } else {
+               td->td_hole_birth_enabled_txg = UINT64_MAX;
+       }
+
+       pd->pd_flags = flags;
+       if (resume != NULL)
+               pd->pd_resume = *resume;
+       mutex_init(&pd->pd_mtx, NULL, MUTEX_DEFAULT, NULL);
+       cv_init(&pd->pd_cv, NULL, CV_DEFAULT, NULL);
+
+       SET_BOOKMARK(czb, td->td_objset,
+           ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
+
+       /* See comment on ZIL traversal in dsl_scan_visitds. */
+       if (ds != NULL && !ds->ds_is_snapshot && !BP_IS_HOLE(rootbp)) {
+               enum zio_flag zio_flags = ZIO_FLAG_CANFAIL;
+               uint32_t flags = ARC_FLAG_WAIT;
+               objset_phys_t *osp;
+               arc_buf_t *buf;
+
+               err = arc_read(NULL, td->td_spa, rootbp, arc_getbuf_func,
+                   &buf, ZIO_PRIORITY_ASYNC_READ, zio_flags, &flags, czb);
+               if (err != 0) {
+                       /*
+                        * If both TRAVERSE_HARD and TRAVERSE_PRE are set,
+                        * continue to visitbp so that td_func can be called
+                        * in pre stage, and err will reset to zero.
+                        */
+                       if (!(td->td_flags & TRAVERSE_HARD) ||
+                           !(td->td_flags & TRAVERSE_PRE))
+                               return (err);
+               } else {
+                       osp = buf->b_data;
+                       traverse_zil(td, &osp->os_zil_header);
+                       arc_buf_destroy(buf, &buf);
+               }
+       }
+
+       if (!(flags & TRAVERSE_PREFETCH_DATA) ||
+           taskq_dispatch(spa->spa_prefetch_taskq, traverse_prefetch_thread,
+           td, TQ_NOQUEUE) == TASKQID_INVALID)
+               pd->pd_exited = B_TRUE;
+
+       err = traverse_visitbp(td, NULL, rootbp, czb);
+
+       mutex_enter(&pd->pd_mtx);
+       pd->pd_cancel = B_TRUE;
+       cv_broadcast(&pd->pd_cv);
+       while (!pd->pd_exited)
+               cv_wait_sig(&pd->pd_cv, &pd->pd_mtx);
+       mutex_exit(&pd->pd_mtx);
+
+       mutex_destroy(&pd->pd_mtx);
+       cv_destroy(&pd->pd_cv);
+
+       kmem_free(czb, sizeof (zbookmark_phys_t));
+       kmem_free(pd, sizeof (struct prefetch_data));
+       kmem_free(td, sizeof (struct traverse_data));
 
        return (err);
 }
@@ -353,54 +652,98 @@ traverse_impl(spa_t *spa, uint64_t objset, blkptr_t *rootbp,
  * in syncing context).
  */
 int
-traverse_dataset(dsl_dataset_t *ds, uint64_t txg_start, int flags,
+traverse_dataset_resume(dsl_dataset_t *ds, uint64_t txg_start,
+    zbookmark_phys_t *resume,
+    int flags, blkptr_cb_t func, void *arg)
+{
+       return (traverse_impl(ds->ds_dir->dd_pool->dp_spa, ds, ds->ds_object,
+           &dsl_dataset_phys(ds)->ds_bp, txg_start, resume, flags, func, arg));
+}
+
+int
+traverse_dataset(dsl_dataset_t *ds, uint64_t txg_start,
+    int flags, blkptr_cb_t func, void *arg)
+{
+       return (traverse_dataset_resume(ds, txg_start, NULL, flags, func, arg));
+}
+
+int
+traverse_dataset_destroyed(spa_t *spa, blkptr_t *blkptr,
+    uint64_t txg_start, zbookmark_phys_t *resume, int flags,
     blkptr_cb_t func, void *arg)
 {
-       return (traverse_impl(ds->ds_dir->dd_pool->dp_spa, ds->ds_object,
-           &ds->ds_phys->ds_bp, txg_start, flags, func, arg));
+       return (traverse_impl(spa, NULL, ZB_DESTROYED_OBJSET,
+           blkptr, txg_start, resume, flags, func, arg));
 }
 
 /*
  * NB: pool must not be changing on-disk (eg, from zdb or sync context).
  */
 int
-traverse_pool(spa_t *spa, blkptr_cb_t func, void *arg)
+traverse_pool(spa_t *spa, uint64_t txg_start, int flags,
+    blkptr_cb_t func, void *arg)
 {
        int err;
        uint64_t obj;
        dsl_pool_t *dp = spa_get_dsl(spa);
        objset_t *mos = dp->dp_meta_objset;
+       boolean_t hard = (flags & TRAVERSE_HARD);
 
        /* visit the MOS */
-       err = traverse_impl(spa, 0, spa_get_rootblkptr(spa),
-           0, TRAVERSE_PRE, func, arg);
-       if (err)
+       err = traverse_impl(spa, NULL, 0, spa_get_rootblkptr(spa),
+           txg_start, NULL, flags, func, arg);
+       if (err != 0)
                return (err);
 
        /* visit each dataset */
-       for (obj = 1; err == 0; err = dmu_object_next(mos, &obj, FALSE, 0)) {
+       for (obj = 1; err == 0;
+           err = dmu_object_next(mos, &obj, B_FALSE, txg_start)) {
                dmu_object_info_t doi;
 
                err = dmu_object_info(mos, obj, &doi);
-               if (err)
-                       return (err);
+               if (err != 0) {
+                       if (hard)
+                               continue;
+                       break;
+               }
 
-               if (doi.doi_type == DMU_OT_DSL_DATASET) {
+               if (doi.doi_bonus_type == DMU_OT_DSL_DATASET) {
                        dsl_dataset_t *ds;
-                       rw_enter(&dp->dp_config_rwlock, RW_READER);
+                       uint64_t txg = txg_start;
+
+                       dsl_pool_config_enter(dp, FTAG);
                        err = dsl_dataset_hold_obj(dp, obj, FTAG, &ds);
-                       rw_exit(&dp->dp_config_rwlock);
-                       if (err)
-                               return (err);
-                       err = traverse_dataset(ds,
-                           ds->ds_phys->ds_prev_snap_txg, TRAVERSE_PRE,
-                           func, arg);
+                       dsl_pool_config_exit(dp, FTAG);
+                       if (err != 0) {
+                               if (hard)
+                                       continue;
+                               break;
+                       }
+                       if (dsl_dataset_phys(ds)->ds_prev_snap_txg > txg)
+                               txg = dsl_dataset_phys(ds)->ds_prev_snap_txg;
+                       err = traverse_dataset(ds, txg, flags, func, arg);
                        dsl_dataset_rele(ds, FTAG);
-                       if (err)
-                               return (err);
+                       if (err != 0)
+                               break;
                }
        }
        if (err == ESRCH)
                err = 0;
        return (err);
 }
+
+#if defined(_KERNEL) && defined(HAVE_SPL)
+EXPORT_SYMBOL(traverse_dataset);
+EXPORT_SYMBOL(traverse_pool);
+
+module_param(zfs_pd_bytes_max, int, 0644);
+MODULE_PARM_DESC(zfs_pd_bytes_max, "Max number of bytes to prefetch");
+
+module_param_named(ignore_hole_birth, send_holes_without_birth_time, int, 0644);
+MODULE_PARM_DESC(ignore_hole_birth, "Alias for send_holes_without_birth_time");
+
+module_param_named(send_holes_without_birth_time,
+       send_holes_without_birth_time, int, 0644);
+MODULE_PARM_DESC(send_holes_without_birth_time,
+       "Ignore hole_birth txg for zfs send");
+#endif