6267 dn_bonus evicted too early
Reviewed by: Richard Yao <ryao@gentoo.org>
Reviewed by: Xin LI <delphij@freebsd.org>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>

*** 231,243 ****
          /* Data which is unique to data (leaf) blocks: */
  
          /* User callback information. */
          dmu_buf_user_t *db_user;
  
!         uint8_t db_immediate_evict;
          uint8_t db_freed_in_flight;
  
          uint8_t db_dirtycnt;
  } dmu_buf_impl_t;
  
  /* Note: the dbuf hash table is exposed only for the mdb module */
  #define DBUF_MUTEXES 256
--- 231,259 ----
          /* Data which is unique to data (leaf) blocks: */
  
          /* User callback information. */
          dmu_buf_user_t *db_user;
  
!         /*
!          * Evict user data as soon as the dirty and reference
!          * counts are equal.
!          */
!         uint8_t db_user_immediate_evict;
! 
!         /*
!          * This block was freed while a read or write was
!          * active.
!          */
          uint8_t db_freed_in_flight;
  
+         /*
+          * dnode_evict_dbufs() or dnode_evict_bonus() tried to
+          * evict this dbuf, but couldn't due to outstanding
+          * references.  Evict once the refcount drops to 0.
+          */
+         uint8_t db_pending_evict;
+ 
          uint8_t db_dirtycnt;
  } dmu_buf_impl_t;
  
  /* Note: the dbuf hash table is exposed only for the mdb module */
  #define DBUF_MUTEXES 256