[PATCH v9 11/12] mmc: core: add random fault injection

[Per Forlin]

This patch prevents mmc core to be built as a module if mmc fault
injection is selected.

Changes needed to resolve this:
 * remove fault inject module from core.c
 * export should_fail() and init_fault_attr_dentries() in fault-injection.c
 * update documentation fault-injection.txt

On 1 July 2011 18:55, Per Forlin <per.forlin at linaro.org> wrote:
> 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 at linaro.org>
> Acked-by: Kyungmin Park <kyungmin.park at samsung.com>
> Acked-by: Arnd Bergmann <arnd at arndb.de>
> Reviewed-by: Venkatraman S <svenkatr at ti.com>
> Tested-by: Sourav Poddar<sourav.poddar at ti.com>
> Tested-by: Linus Walleij <linus.walleij at linaro.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);
This line prevents mmc core to be built as a module, since there will
be two init_module (the mmc core one and this one) for the same
module.

> +
> +#else /* CONFIG_FAIL_MMC_REQUEST */
> +
> +static void mmc_should_fail_request(struct mmc_host *host,
> +                                   struct mmc_request *mrq)
> +{
> +}
> +
+static int __init fail_mmc_request_debugfs(void)
+{
+}
Add fail_mmc_request_debugfs here and call it from mmc_init()

> +#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
depends on FAULT_INJECTION && MMC

> +       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.
and test how the mmc host driver handle retries from