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, 3 insertions, 3 deletions

diff --git a/module/zfs/dmu_send.c b/module/zfs/dmu_send.c
index 36d811138..108fa098b 100644
--- a/module/zfs/dmu_send.c
+++ b/module/zfs/dmu_send.c
@@ -615,7 +615,7 @@ dmu_send_impl(void *tag, dsl_pool_t *dp, dsl_dataset_t *ds,
 		fromtxg = fromzb->zbm_creation_txg;
 	}
 	dsl_dataset_name(ds, drr->drr_u.drr_begin.drr_toname);
-	if (!dsl_dataset_is_snapshot(ds)) {
+	if (!ds->ds_is_snapshot) {
 		(void) strlcat(drr->drr_u.drr_begin.drr_toname, "@--head--",
 		    sizeof (drr->drr_u.drr_begin.drr_toname));
 	}
@@ -820,7 +820,7 @@ dmu_send_estimate(dsl_dataset_t *ds, dsl_dataset_t *fromds, uint64_t *sizep)
 	ASSERT(dsl_pool_config_held(dp));
 
 	/* tosnap must be a snapshot */
-	if (!dsl_dataset_is_snapshot(ds))
+	if (!ds->ds_is_snapshot)
 		return (SET_ERROR(EINVAL));
 
 	/*
@@ -1057,7 +1057,7 @@ dmu_recv_begin_check(void *arg, dmu_tx_t *tx)
 				dsl_dataset_rele(ds, FTAG);
 				return (error);
 			}
-			if (!dsl_dataset_is_snapshot(origin)) {
+			if (!origin->ds_is_snapshot) {
 				dsl_dataset_rele(origin, FTAG);
 				dsl_dataset_rele(ds, FTAG);
 				return (SET_ERROR(EINVAL));