Illumos 5056 - ZFS deadlock on db_mtx and dn_holds

5056 ZFS deadlock on db_mtx and dn_holds
Author: Justin Gibbs <[email protected]>
Reviewed by: Will Andrews <[email protected]>
Reviewed by: Matt Ahrens <[email protected]>
Reviewed by: George Wilson <[email protected]>
Approved by: Dan McDonald <[email protected]>

References:
  https://www.illumos.org/issues/5056
  https://github.com/illumos/illumos-gate/commit/bc9014e

Porting Notes:

sa_handle_get_from_db():
  - the original patch includes an otherwise unmentioned fix for a
    possible usage of an uninitialised variable

dmu_objset_open_impl():
  - Under Illumos list_link_init() is the same as filling a list_node_t
    with NULLs, so they don't notice if they miss doing list_link_init()
    on a zero'd containing structure (e.g. allocated with kmem_zalloc as
    here). Under Linux, not so much: an uninitialised list_node_t goes
    "Boom!" some time later when it's used or destroyed.

dmu_objset_evict_dbufs():
  - reduce stack usage using kmem_alloc()

Ported-by: Chris Dunlop <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>

1 files changed, 6 insertions, 8 deletions

diff --git a/module/zfs/dsl_prop.c b/module/zfs/dsl_prop.c
index 95e0fa6e3..4c0e57990 100644
--- a/module/zfs/dsl_prop.c
+++ b/module/zfs/dsl_prop.c
@@ -163,19 +163,17 @@ dsl_prop_get_ds(dsl_dataset_t *ds, const char *propname,
 {
 	zfs_prop_t prop = zfs_name_to_prop(propname);
 	boolean_t inheritable;
-	boolean_t snapshot;
 	uint64_t zapobj;
 
 	ASSERT(dsl_pool_config_held(ds->ds_dir->dd_pool));
 	inheritable = (prop == ZPROP_INVAL || zfs_prop_inheritable(prop));
-	snapshot = dsl_dataset_is_snapshot(ds);
 	zapobj = dsl_dataset_phys(ds)->ds_props_obj;
 
 	if (zapobj != 0) {
 		objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
 		int err;
 
-		ASSERT(snapshot);
+		ASSERT(ds->ds_is_snapshot);
 
 		/* Check for a local value. */
 		err = zap_lookup(mos, zapobj, propname, intsz, numints, buf);
@@ -215,7 +213,7 @@ dsl_prop_get_ds(dsl_dataset_t *ds, const char *propname,
 	}
 
 	return (dsl_prop_get_dd(ds->ds_dir, propname,
-	    intsz, numints, buf, setpoint, snapshot));
+	    intsz, numints, buf, setpoint, ds->ds_is_snapshot));
 }
 
 /*
@@ -545,7 +543,7 @@ dsl_prop_set_sync_impl(dsl_dataset_t *ds, const char *propname,
 
 	isint = (dodefault(propname, 8, 1, &intval) == 0);
 
-	if (dsl_dataset_is_snapshot(ds)) {
+	if (ds->ds_is_snapshot) {
 		ASSERT(version >= SPA_VERSION_SNAP_PROPS);
 		if (dsl_dataset_phys(ds)->ds_props_obj == 0) {
 			dmu_buf_will_dirty(ds->ds_dbuf, tx);
@@ -642,7 +640,7 @@ dsl_prop_set_sync_impl(dsl_dataset_t *ds, const char *propname,
 	if (isint) {
 		VERIFY0(dsl_prop_get_int_ds(ds, propname, &intval));
 
-		if (dsl_dataset_is_snapshot(ds)) {
+		if (ds->ds_is_snapshot) {
 			dsl_prop_cb_record_t *cbr;
 			/*
 			 * It's a snapshot; nothing can inherit this
@@ -760,7 +758,7 @@ dsl_props_set_check(void *arg, dmu_tx_t *tx)
 		}
 	}
 
-	if (dsl_dataset_is_snapshot(ds) && version < SPA_VERSION_SNAP_PROPS) {
+	if (ds->ds_is_snapshot && version < SPA_VERSION_SNAP_PROPS) {
 		dsl_dataset_rele(ds, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
@@ -983,7 +981,7 @@ dsl_prop_get_all_ds(dsl_dataset_t *ds, nvlist_t **nvp,
 
 	VERIFY(nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_SLEEP) == 0);
 
-	if (dsl_dataset_is_snapshot(ds))
+	if (ds->ds_is_snapshot)
 		flags |= DSL_PROP_GET_SNAPSHOT;
 
 	ASSERT(dsl_pool_config_held(dp));