patch first-pass

*** 531,541 ****
          /*
           * Asynchronous user eviction callback state.
           */
          taskq_ent_t     dbu_tqent;
  
!         /* This instance's eviction function pointer. */
          dmu_buf_evict_func_t *dbu_evict_func;
  #ifdef ZFS_DEBUG
          /*
           * Pointer to user's dbuf pointer.  NULL for clients that do
           * not associate a dbuf with their user data.
--- 531,547 ----
          /*
           * Asynchronous user eviction callback state.
           */
          taskq_ent_t     dbu_tqent;
  
!         /*
!          * This instance's eviction function pointers.
!          *
!          * dbu_evict_func_prep is called synchronously while dbu_evict_func
!          * is executed asynchronously on a taskq.
!          */
!         dmu_buf_evict_func_t *dbu_evict_func_prep;
          dmu_buf_evict_func_t *dbu_evict_func;
  #ifdef ZFS_DEBUG
          /*
           * Pointer to user's dbuf pointer.  NULL for clients that do
           * not associate a dbuf with their user data.
*** 555,573 ****
   *       To allow enforcement of this, dbu must already be zeroed on entry.
   */
  #ifdef __lint
  /* Very ugly, but it beats issuing suppression directives in many Makefiles. */
  extern void
! dmu_buf_init_user(dmu_buf_user_t *dbu, dmu_buf_evict_func_t *evict_func,
!     dmu_buf_t **clear_on_evict_dbufp);
  #else /* __lint */
  inline void
! dmu_buf_init_user(dmu_buf_user_t *dbu, dmu_buf_evict_func_t *evict_func,
!     dmu_buf_t **clear_on_evict_dbufp)
  {
          ASSERT(dbu->dbu_evict_func == NULL);
          ASSERT(evict_func != NULL);
          dbu->dbu_evict_func = evict_func;
  #ifdef ZFS_DEBUG
          dbu->dbu_clear_on_evict_dbufp = clear_on_evict_dbufp;
  #endif
  }
--- 561,581 ----
   *       To allow enforcement of this, dbu must already be zeroed on entry.
   */
  #ifdef __lint
  /* Very ugly, but it beats issuing suppression directives in many Makefiles. */
  extern void
! dmu_buf_init_user(dmu_buf_user_t *dbu, dmu_buf_evict_func_t *evict_func_prep,
!     dmu_buf_evict_func_t *evict_func, dmu_buf_t **clear_on_evict_dbufp);
  #else /* __lint */
  inline void
! dmu_buf_init_user(dmu_buf_user_t *dbu, dmu_buf_evict_func_t *evict_func_prep,
!     dmu_buf_evict_func_t *evict_func, dmu_buf_t **clear_on_evict_dbufp)
  {
+         ASSERT(dbu->dbu_evict_func_prep == NULL);
          ASSERT(dbu->dbu_evict_func == NULL);
          ASSERT(evict_func != NULL);
+         dbu->dbu_evict_func_prep = evict_func_prep;
          dbu->dbu_evict_func = evict_func;
  #ifdef ZFS_DEBUG
          dbu->dbu_clear_on_evict_dbufp = clear_on_evict_dbufp;
  #endif
  }