Fix CPU_SEQID use in preemptible context

Commit e022864 introduced a regression for kernels which are built with CONFIG_DEBUG_PREEMPT. The use of CPU_SEQID in a preemptible context causes zio_nowait() to trigger the BUG. Since CPU_SEQID is simply being used as a random index the usage here is safe. To resolve the issue preempt is disable while calling CPU_SEQID. Signed-off-by: Brian Behlendorf <[email protected]> Signed-off-by: Ned Bass <[email protected]> Closes openzfs#2769
ryao · Oct 7, 2014 · 8878261 · 8878261
1 parent a215ee1
commit 8878261
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/module/zfs/zio.c b/module/zfs/zio.c
@@ -1467,14 +1467,19 @@ zio_nowait(zio_t *zio)
 
 	if (zio->io_child_type == ZIO_CHILD_LOGICAL &&
 	    zio_unique_parent(zio) == NULL) {
+		zio_t *pio;
+
 		/*
 		 * This is a logical async I/O with no parent to wait for it.
 		 * We add it to the spa_async_root_zio "Godfather" I/O which
 		 * will ensure they complete prior to unloading the pool.
 		 */
 		spa_t *spa = zio->io_spa;
+		kpreempt_disable();
+		pio = spa->spa_async_zio_root[CPU_SEQID];
+		kpreempt_enable();
 
-		zio_add_child(spa->spa_async_zio_root[CPU_SEQID], zio);
+		zio_add_child(pio, zio);
 	}
 
 	__zio_execute(zio);