MFV r302991: 6950 ARC should cache compressed data

illumos/illumos-gate@dcbf3bd6a1f1360fc1afcee9e22c6dcff7844bf2
https://github.com/illumos/illumos-gate/commit/dcbf3bd6a1f1360fc1afcee9e22c6dcff7844bf2

https://www.illumos.org/issues/6950
  When reading compressed data from disk, the ARC should keep the compressed
  block cached and only decompress it when consumers access the block. The
  uncompressed data should be short-lived allowing the ARC to cache a much larger
  amount of data. The DMU would also maintain a smaller cache of uncompressed
  blocks to minimize the impact of decompressing frequently accessed blocks.

Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Don Brady <don.brady@intel.com>
Reviewed by: Richard Elling <Richard.Elling@RichardElling.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: George Wilson <george.wilson@delphix.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/refcount.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/refcount.c
index ade681c1de8e..8f7914f87eb2 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/refcount.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/refcount.c
@@ -231,4 +231,28 @@ refcount_transfer(refcount_t *dst, refcount_t *src)
 	list_destroy(&removed);
 }
 
+void
+refcount_transfer_ownership(refcount_t *rc, void *current_holder,
+    void *new_holder)
+{
+	reference_t *ref;
+	boolean_t found = B_FALSE;
+
+	mutex_enter(&rc->rc_mtx);
+	if (!rc->rc_tracked) {
+		mutex_exit(&rc->rc_mtx);
+		return;
+	}
+
+	for (ref = list_head(&rc->rc_list); ref;
+	    ref = list_next(&rc->rc_list, ref)) {
+		if (ref->ref_holder == current_holder) {
+			ref->ref_holder = new_holder;
+			found = B_TRUE;
+			break;
+		}
+	}
+	ASSERT(found);
+	mutex_exit(&rc->rc_mtx);
+}
 #endif	/* ZFS_DEBUG */