Illumos 6267 - dn_bonus evicted too early

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>

References:
  https://www.illumos.org/issues/6267
  https://github.com/illumos/illumos-gate/commit/d205810

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Ported-by: Ned Bass bass6@llnl.gov
Issue #3865
Issue #3443

include/sys/dbuf.h

@@ -230,9 +230,25 @@ typedef struct dmu_buf_impl {
 	/* User callback information. */
 	dmu_buf_user_t *db_user;
 
-	uint8_t db_immediate_evict;
+	/*
+	 * 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;
 

include/sys/dmu_objset.h

@@ -93,7 +93,6 @@ struct objset {
 	uint8_t os_copies;
 	enum zio_checksum os_dedup_checksum;
 	boolean_t os_dedup_verify;
-	boolean_t os_evicting;
 	zfs_logbias_op_t os_logbias;
 	zfs_cache_type_t os_primary_cache;
 	zfs_cache_type_t os_secondary_cache;