block: add sysfs knob for turning off disk entropy contributions

[linux-block.git] / block / blk-sysfs.c

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 306759bbdf1be719ef1f8e0a1f1912475c521a09..58b53c354c2c04251dff85c57f9044eb81c17299 100644 (file)
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -250,6 +250,27 @@ queue_rq_affinity_store(struct request_queue *q, const char *page, size_t count)
        return ret;
 }
 
+static ssize_t queue_random_show(struct request_queue *q, char *page)
+{
+       return queue_var_show(blk_queue_add_random(q), page);
+}
+
+static ssize_t queue_random_store(struct request_queue *q, const char *page,
+                                 size_t count)
+{
+       unsigned long val;
+       ssize_t ret = queue_var_store(&val, page, count);
+
+       spin_lock_irq(q->queue_lock);
+       if (val)
+               queue_flag_set(QUEUE_FLAG_ADD_RANDOM, q);
+       else
+               queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, q);
+       spin_unlock_irq(q->queue_lock);
+
+       return ret;
+}
+
 static ssize_t queue_iostats_show(struct request_queue *q, char *page)
 {
        return queue_var_show(blk_queue_io_stat(q), page);
@@ -374,6 +395,12 @@ static struct queue_sysfs_entry queue_iostats_entry = {
        .store = queue_iostats_store,
 };
 
+static struct queue_sysfs_entry queue_random_entry = {
+       .attr = {.name = "add_random", .mode = S_IRUGO | S_IWUSR },
+       .show = queue_random_show,
+       .store = queue_random_store,
+};
+
 static struct attribute *default_attrs[] = {
        &queue_requests_entry.attr,
        &queue_ra_entry.attr,
@@ -394,6 +421,7 @@ static struct attribute *default_attrs[] = {
        &queue_nomerges_entry.attr,
        &queue_rq_affinity_entry.attr,
        &queue_iostats_entry.attr,
+       &queue_random_entry.attr,
        NULL,
 };