null_blk: add option for managing IO timeouts

Use the fault injection framework to provide a way for null_blk
to configure timeouts. This only works for queue_mode 1 and 2,
since the bio mode doesn't have code for tracking timeouts.

Let's say you want to have a 10% chance of timing out every
100,000 requests, and for 5 total timeouts, you could do:

modprobe null_blk timeout="100000,10,0,5"

This is useful for adding blktests to test that IO timeouts
are handled appropriately.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 40579d0cb3d114ba2fb635857e8ea9881bec7d74..622d9a2c8daeb199315fc2ea6dbd42f84cff137f 100644 (file)
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -19,6 +19,7 @@ if BLK_DEV
 config BLK_DEV_NULL_BLK
        tristate "Null test block driver"
        select CONFIGFS_FS
+       select FAULT_INJECTION
 
 config BLK_DEV_FD
        tristate "Normal floppy disk support"

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 78267e3e4fa528737df00fdcd2f2367ad68f4c2f..30ec0ac11a47ddb075d5b46614abd8e7fbd171d1 100644 (file)
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -14,6 +14,7 @@
 #include <linux/hrtimer.h>
 #include <linux/configfs.h>
 #include <linux/badblocks.h>
+#include <linux/fault-inject.h>
 
 #define SECTOR_SHIFT           9
 #define PAGE_SECTORS_SHIFT     (PAGE_SHIFT - SECTOR_SHIFT)
@@ -26,6 +27,8 @@
 #define TICKS_PER_SEC          50ULL
 #define TIMER_INTERVAL         (NSEC_PER_SEC / TICKS_PER_SEC)
 
+static DECLARE_FAULT_ATTR(null_timeout_attr);
+
 static inline u64 mb_per_tick(int mbps)
 {
        return (1 << 20) / TICKS_PER_SEC * ((u64) mbps);
@@ -162,6 +165,9 @@ static int g_home_node = NUMA_NO_NODE;
 module_param_named(home_node, g_home_node, int, S_IRUGO);
 MODULE_PARM_DESC(home_node, "Home node for the device");
 
+static char g_timeout_str[80];
+module_param_string(timeout, g_timeout_str, sizeof(g_timeout_str), S_IRUGO);
+
 static int g_queue_mode = NULL_Q_MQ;
 
 static int null_param_store_val(const char *str, int *val, int min, int max)
@@ -1364,6 +1370,14 @@ static int null_rq_prep_fn(struct request_queue *q, struct request *req)
        return BLKPREP_DEFER;
 }
 
+static bool should_timeout_request(struct request *rq)
+{
+       if (g_timeout_str[0])
+               return should_fail(&null_timeout_attr, 1);
+
+       return false;
+}
+
 static void null_request_fn(struct request_queue *q)
 {
        struct request *rq;
@@ -1371,9 +1385,11 @@ static void null_request_fn(struct request_queue *q)
        while ((rq = blk_fetch_request(q)) != NULL) {
                struct nullb_cmd *cmd = rq->special;
 
-               spin_unlock_irq(q->queue_lock);
-               null_handle_cmd(cmd);
-               spin_lock_irq(q->queue_lock);
+               if (!should_timeout_request(rq)) {
+                       spin_unlock_irq(q->queue_lock);
+                       null_handle_cmd(cmd);
+                       spin_lock_irq(q->queue_lock);
+               }
        }
 }
 
@@ -1400,7 +1416,10 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
 
        blk_mq_start_request(bd->rq);
 
-       return null_handle_cmd(cmd);
+       if (!should_timeout_request(bd->rq))
+               return null_handle_cmd(cmd);
+
+       return BLK_STS_OK;
 }
 
 static const struct blk_mq_ops null_mq_ops = {
@@ -1634,6 +1653,18 @@ static void null_validate_conf(struct nullb_device *dev)
                dev->mbps = 0;
 }
 
+static bool null_setup_fault(void)
+{
+       if (!g_timeout_str[0])
+               return true;
+
+       if (!setup_fault_attr(&null_timeout_attr, g_timeout_str))
+               return false;
+
+       null_timeout_attr.verbose = 0;
+       return true;
+}
+
 static int null_add_dev(struct nullb_device *dev)
 {
        struct nullb *nullb;
@@ -1667,6 +1698,9 @@ static int null_add_dev(struct nullb_device *dev)
                if (rv)
                        goto out_cleanup_queues;
 
+               if (!null_setup_fault())
+                       goto out_cleanup_queues;
+
                nullb->tag_set->timeout = 5 * HZ;
                nullb->q = blk_mq_init_queue(nullb->tag_set);
                if (IS_ERR(nullb->q)) {
@@ -1691,6 +1725,10 @@ static int null_add_dev(struct nullb_device *dev)
                        rv = -ENOMEM;
                        goto out_cleanup_queues;
                }
+
+               if (!null_setup_fault())
+                       goto out_cleanup_blk_queue;
+
                blk_queue_prep_rq(nullb->q, null_rq_prep_fn);
                blk_queue_softirq_done(nullb->q, null_softirq_done_fn);
                blk_queue_rq_timed_out(nullb->q, null_rq_timed_out_fn);