[PATCH v8 11/12] mmc: core: add random fault injection

Per Forlin
2011-06-28T08:11:56Z

This simple fault injection proved to be very useful to
test the error handling in the block.c rw_rq(). It may
still be useful to test if the host driver handle
pre_req() and post_req() correctly in case of errors.

Signed-off-by: Per Forlin <per.forlin-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
drivers/mmc/core/core.c | 54 ++++++++++++++++++++++++++++++++++++++++++++
drivers/mmc/core/debugfs.c | 5 ++++
include/linux/mmc/host.h | 3 ++
lib/Kconfig.debug | 11 +++++++++
4 files changed, 73 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index d2d7239..62a8cc7 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -23,6 +23,8 @@
#include <linux/log2.h>
#include <linux/regulator/consumer.h>
#include <linux/pm_runtime.h>
+#include <linux/fault-inject.h>
+#include <linux/random.h>

#include <linux/mmc/card.h>
#include <linux/mmc/host.h>
@@ -82,6 +84,56 @@ static void mmc_flush_scheduled_work(void)
flush_workqueue(workqueue);
}

+#ifdef CONFIG_FAIL_MMC_REQUEST
+
+static DECLARE_FAULT_ATTR(fail_mmc_request);
+
+static int __init setup_fail_mmc_request(char *str)
+{
+ return setup_fault_attr(&fail_mmc_request, str);
+}
+__setup("fail_mmc_request=", setup_fail_mmc_request);
+
+static void mmc_should_fail_request(struct mmc_host *host,
+ struct mmc_request *mrq)
+{
+ struct mmc_command *cmd = mrq->cmd;
+ struct mmc_data *data = mrq->data;
+ static const int data_errors[] = {
+ -ETIMEDOUT,
+ -EILSEQ,
+ -EIO,
+ };
+
+ if (!data)
+ return;
+
+ if (cmd->error || data->error || !host->make_it_fail ||
+ !should_fail(&fail_mmc_request, data->blksz * data->blocks))
+ return;
+
+ data->error = data_errors[random32() % ARRAY_SIZE(data_errors)];
+ data->bytes_xfered = (random32() % (data->bytes_xfered >> 9)) << 9;
+}
+
+static int __init fail_mmc_request_debugfs(void)
+{
+ return init_fault_attr_dentries(&fail_mmc_request,
+ "fail_mmc_request");
+}
+
+late_initcall(fail_mmc_request_debugfs);
+
+#else /* CONFIG_FAIL_MMC_REQUEST */
+
+static void mmc_should_fail_request(struct mmc_host *host,
+ struct mmc_request *mrq)
+{
+}
+
+#endif /* CONFIG_FAIL_MMC_REQUEST */
+
+
/**
* mmc_request_done - finish processing an MMC request
* @host: MMC host which completed request
@@ -108,6 +160,8 @@ void mmc_request_done(struct mmc_host *host, struct mmc_request *mrq)
cmd->error = 0;
host->ops->request(host, mrq);
} else {
+ mmc_should_fail_request(host, mrq);
+
led_trigger_event(host->led, LED_OFF);

pr_debug("%s: req done (CMD%u): %d: %08x %08x %08x %08x\n",
diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
index 998797e..588e76f 100644
--- a/drivers/mmc/core/debugfs.c
+++ b/drivers/mmc/core/debugfs.c
@@ -188,6 +188,11 @@ void mmc_add_host_debugfs(struct mmc_host *host)
root, &host->clk_delay))
goto err_node;
#endif
+#ifdef CONFIG_FAIL_MMC_REQUEST
+ if (!debugfs_create_u8("make-it-fail", S_IRUSR | S_IWUSR,
+ root, &host->make_it_fail))
+ goto err_node;
+#endif
return;

err_node:
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 59db6f2..0d0a48f 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -301,6 +301,9 @@ struct mmc_host {

struct mmc_async_req *areq; /* active async req */

+#ifdef CONFIG_FAIL_MMC_REQUEST
+ u8 make_it_fail;
+#endif
unsigned long private[0] ____cacheline_aligned;
};

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c768bcd..330fc70 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1057,6 +1057,17 @@ config FAIL_IO_TIMEOUT
Only works with drivers that use the generic timeout handling,
for others it wont do anything.

+config FAIL_MMC_REQUEST
+ bool "Fault-injection capability for MMC IO"
+ select DEBUG_FS
+ depends on FAULT_INJECTION
+ help
+ Provide fault-injection capability for MMC IO.
+ This will make the mmc core return data errors. This is
+ useful for testing the error handling in the mmc block device
+ and how the mmc host driver handle retries from
+ the block device.
+
config FAULT_INJECTION_DEBUG_FS
bool "Debugfs entries for fault-injection capabilities"
depends on FAULT_INJECTION && SYSFS && DEBUG_FS
--
1.7.4.1