3740 Poor ZFS send / receive performance due to snapshot hold / release processing
Submitted by: Steven Hartland <steven.hartland@multiplay.co.uk>

*** 4079,4126 ****
  
  static int
  zfs_hold_one(zfs_handle_t *zhp, void *arg)
  {
          struct holdarg *ha = arg;
-         zfs_handle_t *szhp;
          char name[ZFS_MAXNAMELEN];
          int rv = 0;
  
          (void) snprintf(name, sizeof (name),
              "%s@%s", zhp->zfs_name, ha->snapname);
  
!         szhp = make_dataset_handle(zhp->zfs_hdl, name);
!         if (szhp) {
                  fnvlist_add_string(ha->nvl, name, ha->tag);
-                 zfs_close(szhp);
-         }
  
          if (ha->recursive)
                  rv = zfs_iter_filesystems(zhp, zfs_hold_one, ha);
          zfs_close(zhp);
          return (rv);
  }
  
  int
  zfs_hold(zfs_handle_t *zhp, const char *snapname, const char *tag,
!     boolean_t recursive, boolean_t enoent_ok, int cleanup_fd)
  {
          int ret;
          struct holdarg ha;
-         nvlist_t *errors;
-         libzfs_handle_t *hdl = zhp->zfs_hdl;
-         char errbuf[1024];
-         nvpair_t *elem;
  
          ha.nvl = fnvlist_alloc();
          ha.snapname = snapname;
          ha.tag = tag;
          ha.recursive = recursive;
          (void) zfs_hold_one(zfs_handle_dup(zhp), &ha);
!         ret = lzc_hold(ha.nvl, cleanup_fd, &errors);
          fnvlist_free(ha.nvl);
  
          if (ret == 0)
                  return (0);
  
          if (nvlist_next_nvpair(errors, NULL) == NULL) {
                  /* no hold-specific errors */
--- 4079,4132 ----
  
  static int
  zfs_hold_one(zfs_handle_t *zhp, void *arg)
  {
          struct holdarg *ha = arg;
          char name[ZFS_MAXNAMELEN];
          int rv = 0;
  
          (void) snprintf(name, sizeof (name),
              "%s@%s", zhp->zfs_name, ha->snapname);
  
!         if (lzc_exists(name))
                  fnvlist_add_string(ha->nvl, name, ha->tag);
  
          if (ha->recursive)
                  rv = zfs_iter_filesystems(zhp, zfs_hold_one, ha);
          zfs_close(zhp);
          return (rv);
  }
  
  int
  zfs_hold(zfs_handle_t *zhp, const char *snapname, const char *tag,
!     boolean_t recursive, int cleanup_fd)
  {
          int ret;
          struct holdarg ha;
  
          ha.nvl = fnvlist_alloc();
          ha.snapname = snapname;
          ha.tag = tag;
          ha.recursive = recursive;
          (void) zfs_hold_one(zfs_handle_dup(zhp), &ha);
!         ret = zfs_hold_nvl(zhp, cleanup_fd, ha.nvl);
          fnvlist_free(ha.nvl);
  
+         return (ret);
+ }
+ 
+ int
+ zfs_hold_nvl(zfs_handle_t *zhp, int cleanup_fd, nvlist_t *holds)
+ {
+         int ret;
+         nvlist_t *errors;
+         libzfs_handle_t *hdl = zhp->zfs_hdl;
+         char errbuf[1024];
+         nvpair_t *elem;
+  
+         ret = lzc_hold(holds, cleanup_fd, &errors);
+  
          if (ret == 0)
                  return (0);
  
          if (nvlist_next_nvpair(errors, NULL) == NULL) {
                  /* no hold-specific errors */
*** 4160,4207 ****
                          (void) zfs_error(hdl, EZFS_BADTYPE, errbuf);
                          break;
                  case EEXIST:
                          (void) zfs_error(hdl, EZFS_REFTAG_HOLD, errbuf);
                          break;
-                 case ENOENT:
-                         if (enoent_ok)
-                                 return (ENOENT);
-                         /* FALLTHROUGH */
                  default:
                          (void) zfs_standard_error(hdl,
                              fnvpair_value_int32(elem), errbuf);
                  }
          }
  
          fnvlist_free(errors);
          return (ret);
  }
  
- struct releasearg {
-         nvlist_t *nvl;
-         const char *snapname;
-         const char *tag;
-         boolean_t recursive;
- };
- 
  static int
  zfs_release_one(zfs_handle_t *zhp, void *arg)
  {
          struct holdarg *ha = arg;
-         zfs_handle_t *szhp;
          char name[ZFS_MAXNAMELEN];
          int rv = 0;
  
          (void) snprintf(name, sizeof (name),
              "%s@%s", zhp->zfs_name, ha->snapname);
  
!         szhp = make_dataset_handle(zhp->zfs_hdl, name);
!         if (szhp) {
                  nvlist_t *holds = fnvlist_alloc();
                  fnvlist_add_boolean(holds, ha->tag);
                  fnvlist_add_nvlist(ha->nvl, name, holds);
!                 zfs_close(szhp);
          }
  
          if (ha->recursive)
                  rv = zfs_iter_filesystems(zhp, zfs_release_one, ha);
          zfs_close(zhp);
--- 4166,4200 ----
                          (void) zfs_error(hdl, EZFS_BADTYPE, errbuf);
                          break;
                  case EEXIST:
                          (void) zfs_error(hdl, EZFS_REFTAG_HOLD, errbuf);
                          break;
                  default:
                          (void) zfs_standard_error(hdl,
                              fnvpair_value_int32(elem), errbuf);
                  }
          }
  
          fnvlist_free(errors);
          return (ret);
  }
  
  static int
  zfs_release_one(zfs_handle_t *zhp, void *arg)
  {
          struct holdarg *ha = arg;
          char name[ZFS_MAXNAMELEN];
          int rv = 0;
  
          (void) snprintf(name, sizeof (name),
              "%s@%s", zhp->zfs_name, ha->snapname);
  
!         if (lzc_exists(name)) {
                  nvlist_t *holds = fnvlist_alloc();
                  fnvlist_add_boolean(holds, ha->tag);
                  fnvlist_add_nvlist(ha->nvl, name, holds);
!                 fnvlist_free(holds);
          }
  
          if (ha->recursive)
                  rv = zfs_iter_filesystems(zhp, zfs_release_one, ha);
          zfs_close(zhp);