Add sa_spill_rele() interface

Add a SA interface which allows us to release the spill block
from a SA handle without destroying the handle.  This is useful
because we can then ensure that a copy of the dirty spill block
is not made at sync time due to the extra hold.  Susequent calls
to sa_update() or sa_lookup() with transparently refetch the
spill block dbuf from the ARC hash.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

diff --git a/include/sys/sa.h b/include/sys/sa.h
index 718cbfbd5fc318cf562e4900324082e157c885cf..b8db0c1305cb5ec92ef1366b353f021a97a684fc 100644 (file)
--- a/include/sys/sa.h
+++ b/include/sys/sa.h
@@ -139,6 +139,7 @@ void sa_set_userp(sa_handle_t *, void *);
 dmu_buf_t *sa_get_db(sa_handle_t *);
 uint64_t sa_handle_object(sa_handle_t *);
 boolean_t sa_attr_would_spill(sa_handle_t *, sa_attr_type_t, int size);
+void sa_spill_rele(sa_handle_t *);
 void sa_register_update_callback(objset_t *, sa_update_cb_t *);
 int sa_setup(objset_t *, uint64_t, sa_attr_reg_t *, int, sa_attr_type_t **);
 void sa_tear_down(objset_t *);

diff --git a/module/zfs/sa.c b/module/zfs/sa.c
index bcef7d1fb93d78c74bff71951613b0fd084fccb0..32b4c5b084e1d8f1565251d927f8c45caa6fe5d6 100644 (file)
--- a/module/zfs/sa.c
+++ b/module/zfs/sa.c
@@ -1333,6 +1333,19 @@ sa_idx_tab_hold(objset_t *os, sa_idx_tab_t *idx_tab)
        (void) refcount_add(&idx_tab->sa_refcount, NULL);
 }
 
+void
+sa_spill_rele(sa_handle_t *hdl)
+{
+       mutex_enter(&hdl->sa_lock);
+       if (hdl->sa_spill) {
+               sa_idx_tab_rele(hdl->sa_os, hdl->sa_spill_tab);
+               dmu_buf_rele(hdl->sa_spill, NULL);
+               hdl->sa_spill = NULL;
+               hdl->sa_spill_tab = NULL;
+       }
+       mutex_exit(&hdl->sa_lock);
+}
+
 void
 sa_handle_destroy(sa_handle_t *hdl)
 {
@@ -1994,6 +2007,7 @@ EXPORT_SYMBOL(sa_handle_get_from_db);
 EXPORT_SYMBOL(sa_handle_destroy);
 EXPORT_SYMBOL(sa_buf_hold);
 EXPORT_SYMBOL(sa_buf_rele);
+EXPORT_SYMBOL(sa_spill_rele);
 EXPORT_SYMBOL(sa_lookup);
 EXPORT_SYMBOL(sa_update);
 EXPORT_SYMBOL(sa_remove);