5056 ZFS deadlock on db_mtx and dn_holds
Reviewed by: Will Andrews <willa@spectralogic.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

*** 21,30 ****
--- 21,31 ----
  
  /*
   * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
   * Portions Copyright 2011 iXsystems, Inc
   * Copyright (c) 2013 by Delphix. All rights reserved.
+  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
   */
  
  #include <sys/zfs_context.h>
  #include <sys/types.h>
  #include <sys/param.h>
*** 208,217 ****
--- 209,219 ----
  static int
  sa_cache_constructor(void *buf, void *unused, int kmflag)
  {
          sa_handle_t *hdl = buf;
  
+         hdl->sa_dbu.dbu_evict_func = NULL;
          hdl->sa_bonus_tab = NULL;
          hdl->sa_spill_tab = NULL;
          hdl->sa_os = NULL;
          hdl->sa_userp = NULL;
          hdl->sa_bonus = NULL;
*** 223,232 ****
--- 225,235 ----
  /*ARGSUSED*/
  static void
  sa_cache_destructor(void *buf, void *unused)
  {
          sa_handle_t *hdl = buf;
+         hdl->sa_dbu.dbu_evict_func = NULL;
          mutex_destroy(&hdl->sa_lock);
  }
  
  void
  sa_cache_init(void)
*** 1299,1312 ****
          mutex_exit(&sa->sa_lock);
          return (0);
  }
  
  /*ARGSUSED*/
! void
! sa_evict(dmu_buf_t *db, void *sap)
  {
!         panic("evicting sa dbuf %p\n", (void *)db);
  }
  
  static void
  sa_idx_tab_rele(objset_t *os, void *arg)
  {
--- 1302,1315 ----
          mutex_exit(&sa->sa_lock);
          return (0);
  }
  
  /*ARGSUSED*/
! static void
! sa_evict(void *dbu)
  {
!         panic("evicting sa dbuf\n");
  }
  
  static void
  sa_idx_tab_rele(objset_t *os, void *arg)
  {
*** 1341,1353 ****
  }
  
  void
  sa_handle_destroy(sa_handle_t *hdl)
  {
          mutex_enter(&hdl->sa_lock);
!         (void) dmu_buf_update_user((dmu_buf_t *)hdl->sa_bonus, hdl,
!             NULL, NULL);
  
          if (hdl->sa_bonus_tab) {
                  sa_idx_tab_rele(hdl->sa_os, hdl->sa_bonus_tab);
                  hdl->sa_bonus_tab = NULL;
          }
--- 1344,1357 ----
  }
  
  void
  sa_handle_destroy(sa_handle_t *hdl)
  {
+         dmu_buf_t *db = hdl->sa_bonus;
+ 
          mutex_enter(&hdl->sa_lock);
!         (void) dmu_buf_remove_user(db, &hdl->sa_dbu);
  
          if (hdl->sa_bonus_tab) {
                  sa_idx_tab_rele(hdl->sa_os, hdl->sa_bonus_tab);
                  hdl->sa_bonus_tab = NULL;
          }
*** 1369,1404 ****
  sa_handle_get_from_db(objset_t *os, dmu_buf_t *db, void *userp,
      sa_handle_type_t hdl_type, sa_handle_t **handlepp)
  {
          int error = 0;
          dmu_object_info_t doi;
!         sa_handle_t *handle;
  
  #ifdef ZFS_DEBUG
          dmu_object_info_from_db(db, &doi);
          ASSERT(doi.doi_bonus_type == DMU_OT_SA ||
              doi.doi_bonus_type == DMU_OT_ZNODE);
  #endif
          /* find handle, if it exists */
          /* if one doesn't exist then create a new one, and initialize it */
  
!         handle = (hdl_type == SA_HDL_SHARED) ? dmu_buf_get_user(db) : NULL;
          if (handle == NULL) {
!                 sa_handle_t *newhandle;
                  handle = kmem_cache_alloc(sa_cache, KM_SLEEP);
                  handle->sa_userp = userp;
                  handle->sa_bonus = db;
                  handle->sa_os = os;
                  handle->sa_spill = NULL;
  
                  error = sa_build_index(handle, SA_BONUS);
-                 newhandle = (hdl_type == SA_HDL_SHARED) ?
-                     dmu_buf_set_user_ie(db, handle, sa_evict) : NULL;
  
!                 if (newhandle != NULL) {
                          kmem_cache_free(sa_cache, handle);
!                         handle = newhandle;
                  }
          }
          *handlepp = handle;
  
          return (error);
--- 1373,1414 ----
  sa_handle_get_from_db(objset_t *os, dmu_buf_t *db, void *userp,
      sa_handle_type_t hdl_type, sa_handle_t **handlepp)
  {
          int error = 0;
          dmu_object_info_t doi;
!         sa_handle_t *handle = NULL;
  
  #ifdef ZFS_DEBUG
          dmu_object_info_from_db(db, &doi);
          ASSERT(doi.doi_bonus_type == DMU_OT_SA ||
              doi.doi_bonus_type == DMU_OT_ZNODE);
  #endif
          /* find handle, if it exists */
          /* if one doesn't exist then create a new one, and initialize it */
  
!         if (hdl_type == SA_HDL_SHARED)
!                 handle = dmu_buf_get_user(db);
! 
          if (handle == NULL) {
!                 sa_handle_t *winner = NULL;
! 
                  handle = kmem_cache_alloc(sa_cache, KM_SLEEP);
                  handle->sa_userp = userp;
                  handle->sa_bonus = db;
                  handle->sa_os = os;
                  handle->sa_spill = NULL;
  
                  error = sa_build_index(handle, SA_BONUS);
  
!                 if (hdl_type == SA_HDL_SHARED) {
!                         dmu_buf_init_user(&handle->sa_dbu, sa_evict, NULL);
!                         winner = dmu_buf_set_user_ie(db, &handle->sa_dbu);
!                 }
! 
!                 if (winner != NULL) {
                          kmem_cache_free(sa_cache, handle);
!                         handle = winner;
                  }
          }
          *handlepp = handle;
  
          return (error);
*** 1904,1921 ****
  {
          dmu_object_size_from_db((dmu_buf_t *)hdl->sa_bonus,
              blksize, nblocks);
  }
  
- void
- sa_update_user(sa_handle_t *newhdl, sa_handle_t *oldhdl)
- {
-         (void) dmu_buf_update_user((dmu_buf_t *)newhdl->sa_bonus,
-             oldhdl, newhdl, sa_evict);
-         oldhdl->sa_bonus = NULL;
- }
- 
  void
  sa_set_userp(sa_handle_t *hdl, void *ptr)
  {
          hdl->sa_userp = ptr;
  }
--- 1914,1923 ----