From: Morgan Jones <mjones@rice.edu>
Date: Mon, 19 Jun 2017 16:43:16 +0000 (+0000)
Subject: Add kpreempt_disable/enable around CPU_SEQID uses
X-Git-Tag: zfs-0.7.0-rc5~45
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d9ad3fea3bd0368b6af0b08ccc4de1b080e2bcb7;p=zfs

Add kpreempt_disable/enable around CPU_SEQID uses

In zfs/dmu_object and icp/core/kcf_sched, the CPU_SEQID macro
should be surrounded by `kpreempt_disable` and `kpreempt_enable`
calls to avoid a Linux kernel BUG warning.  These code paths use
the cpuid to minimize lock contention and is is safe to reschedule
the process to a different processor at any time.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Morgan Jones <me@numin.it>
Closes #6239
---

diff --git a/module/icp/core/kcf_sched.c b/module/icp/core/kcf_sched.c
index f9bcfe094..da2346f7e 100644
--- a/module/icp/core/kcf_sched.c
+++ b/module/icp/core/kcf_sched.c
@@ -1306,8 +1306,11 @@ kcf_reqid_insert(kcf_areq_node_t *areq)
 	int indx;
 	crypto_req_id_t id;
 	kcf_areq_node_t *headp;
-	kcf_reqid_table_t *rt =
-	    kcf_reqid_table[CPU_SEQID & REQID_TABLE_MASK];
+	kcf_reqid_table_t *rt;
+
+	kpreempt_disable();
+	rt = kcf_reqid_table[CPU_SEQID & REQID_TABLE_MASK];
+	kpreempt_enable();
 
 	mutex_enter(&rt->rt_lock);
 
diff --git a/module/zfs/dmu_object.c b/module/zfs/dmu_object.c
index cb861a196..1c7b26d4b 100644
--- a/module/zfs/dmu_object.c
+++ b/module/zfs/dmu_object.c
@@ -59,10 +59,14 @@ dmu_object_alloc_dnsize(objset_t *os, dmu_object_type_t ot, int blocksize,
 	dnode_t *dn = NULL;
 	int dn_slots = dnodesize >> DNODE_SHIFT;
 	boolean_t restarted = B_FALSE;
-	uint64_t *cpuobj = &os->os_obj_next_percpu[CPU_SEQID %
-	    os->os_obj_next_percpu_len];
+	uint64_t *cpuobj = NULL;
 	int dnodes_per_chunk = 1 << dmu_object_alloc_chunk_shift;
 
+	kpreempt_disable();
+	cpuobj = &os->os_obj_next_percpu[CPU_SEQID %
+	    os->os_obj_next_percpu_len];
+	kpreempt_enable();
+
 	if (dn_slots == 0) {
 		dn_slots = DNODE_MIN_SLOTS;
 	} else {