MFC r286575: 5056 ZFS deadlock on db_mtx and dn_holds

Reviewed by: Will Andrews <willa@spectralogic.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Justin Gibbs <justing@spectralogic.com>

illumos/illumos-gate@bc9014e6a81272073b9854d9f65dd59e18d18c35

1 files changed, 21 insertions, 20 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sa.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sa.c
index 0302647..dfdb38c 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sa.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sa.c
@@ -23,6 +23,7 @@
  * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
  * Portions Copyright 2011 iXsystems, Inc
  * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -219,6 +220,7 @@ static void
 sa_cache_destructor(void *buf, void *unused)
 {
 	sa_handle_t *hdl = buf;
+	hdl->sa_dbu.dbu_evict_func = NULL;
 	mutex_destroy(&hdl->sa_lock);
 }
 
@@ -1298,10 +1300,10 @@ sa_build_index(sa_handle_t *hdl, sa_buf_type_t buftype)
 }
 
 /*ARGSUSED*/
-void
-sa_evict(dmu_buf_t *db, void *sap)
+static void
+sa_evict(void *dbu)
 {
-	panic("evicting sa dbuf %p\n", (void *)db);
+	panic("evicting sa dbuf\n");
 }
 
 static void
@@ -1340,9 +1342,10 @@ sa_idx_tab_hold(objset_t *os, sa_idx_tab_t *idx_tab)
 void
 sa_handle_destroy(sa_handle_t *hdl)
 {
+	dmu_buf_t *db = hdl->sa_bonus;
+
 	mutex_enter(&hdl->sa_lock);
-	(void) dmu_buf_update_user((dmu_buf_t *)hdl->sa_bonus, hdl,
-	    NULL, NULL);
+	(void) dmu_buf_remove_user(db, &hdl->sa_dbu);
 
 	if (hdl->sa_bonus_tab)
 		sa_idx_tab_rele(hdl->sa_os, hdl->sa_bonus_tab);
@@ -1365,7 +1368,7 @@ sa_handle_get_from_db(objset_t *os, dmu_buf_t *db, void *userp,
 {
 	int error = 0;
 	dmu_object_info_t doi;
-	sa_handle_t *handle;
+	sa_handle_t *handle = NULL;
 
 #ifdef ZFS_DEBUG
 	dmu_object_info_from_db(db, &doi);
@@ -1375,9 +1378,12 @@ sa_handle_get_from_db(objset_t *os, dmu_buf_t *db, void *userp,
 	/* find handle, if it exists */
 	/* if one doesn't exist then create a new one, and initialize it */
 
-	handle = (hdl_type == SA_HDL_SHARED) ? dmu_buf_get_user(db) : NULL;
+	if (hdl_type == SA_HDL_SHARED)
+		handle = dmu_buf_get_user(db);
+
 	if (handle == NULL) {
-		sa_handle_t *newhandle;
+		sa_handle_t *winner = NULL;
+
 		handle = kmem_cache_alloc(sa_cache, KM_SLEEP);
 		handle->sa_userp = userp;
 		handle->sa_bonus = db;
@@ -1387,12 +1393,15 @@ sa_handle_get_from_db(objset_t *os, dmu_buf_t *db, void *userp,
 		handle->sa_spill_tab = NULL;
 
 		error = sa_build_index(handle, SA_BONUS);
-		newhandle = (hdl_type == SA_HDL_SHARED) ?
-		    dmu_buf_set_user_ie(db, handle, sa_evict) : NULL;
 
-		if (newhandle != NULL) {
+		if (hdl_type == SA_HDL_SHARED) {
+			dmu_buf_init_user(&handle->sa_dbu, sa_evict, NULL);
+			winner = dmu_buf_set_user_ie(db, &handle->sa_dbu);
+		}
+
+		if (winner != NULL) {
 			kmem_cache_free(sa_cache, handle);
-			handle = newhandle;
+			handle = winner;
 		}
 	}
 	*handlepp = handle;
@@ -1910,14 +1919,6 @@ sa_object_size(sa_handle_t *hdl, uint32_t *blksize, u_longlong_t *nblocks)
 }
 
 void
-sa_update_user(sa_handle_t *newhdl, sa_handle_t *oldhdl)
-{
-	(void) dmu_buf_update_user((dmu_buf_t *)newhdl->sa_bonus,
-	    oldhdl, newhdl, sa_evict);
-	oldhdl->sa_bonus = NULL;
-}
-
-void
 sa_set_userp(sa_handle_t *hdl, void *ptr)
 {
 	hdl->sa_userp = ptr;