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Message-ID: <CAJ0pr18MbMj=Np+_0e_F1RmBvRVUhOF5=0ZUUtU4yc_3kKE+cw@mail.gmail.com>
Date: Fri, 19 Aug 2011 14:13:07 +0200
From: Per Forlin <per.forlin@...aro.org>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Akinobu Mita <akinobu.mita@...il.com>, akpm@...ux-foundation.org,
Linus Walleij <linus.ml.walleij@...il.com>,
linux-kernel@...r.kernel.org, Randy Dunlap <rdunlap@...otime.net>,
Chris Ball <cjb@...top.org>, linux-doc@...r.kernel.org,
linux-mmc@...r.kernel.org, linaro-dev@...ts.linaro.org,
linux-mm@...ck.org, J Freyensee <james_p_freyensee@...ux.intel.com>
Subject: Re: [PATCH --mmotm v8 2/3] mmc: core: add random fault injection
On 19 August 2011 13:40, Linus Walleij <linus.walleij@...aro.org> wrote:
> On Tue, Aug 9, 2011 at 2:07 PM, Per Forlin <per.forlin@...aro.org> wrote:
>
>> This adds support to inject data errors after a completed host transfer.
>> The mmc core will return error even though the host transfer is successful.
>> This simple fault injection proved to be very useful to test the
>> non-blocking error handling in the mmc_blk_issue_rw_rq().
>> Random faults can also test how the host driver handles pre_req()
>> and post_req() in case of errors.
>
> Good idea!
>
Thanks.
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index 89bdeae..a4996b0 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -25,6 +25,11 @@
>> #include <linux/pm_runtime.h>
>> #include <linux/suspend.h>
>>
>> +#ifdef CONFIG_FAIL_MMC_REQUEST
>> +#include <linux/fault-inject.h>
>> +#include <linux/random.h>
>> +#endif
>
> You don't need to #ifdef around the #include <> stuff, and if you
> do, something is wrong with those headers. It's just a bunch of defines
> that aren't used in some circumstances. Stack them with the others,
> simply, just #ifdef the code below.
>
I added them after suggestion from J Freyensee. I am also in favor of
no ifdefs here. I'll remove them in the next patchset unless James has
any strong objections.
>> @@ -83,6 +88,43 @@ static void mmc_flush_scheduled_work(void)
>> flush_workqueue(workqueue);
>> }
>>
>> +#ifdef CONFIG_FAIL_MMC_REQUEST
>> +
>> +/*
>> + * Internal function. Inject random data errors.
>> + * If mmc_data is NULL no errors are injected.
>> + */
>> +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 ||
>> + !should_fail(&host->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;
>> +}
>> +
>> +#else /* CONFIG_FAIL_MMC_REQUEST */
>> +
>> +static void mmc_should_fail_request(struct mmc_host *host,
>> + struct mmc_request *mrq)
>
> Should be "static inline" so we know it will be folded in and nullified
> by the compiler, lots of kernel code use that pattern.
>
I'll fix.
>> diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
>> index f573753..189581d 100644
>> --- a/drivers/mmc/core/debugfs.c
>> +++ b/drivers/mmc/core/debugfs.c
>> @@ -13,6 +13,9 @@
>> #include <linux/seq_file.h>
>> #include <linux/slab.h>
>> #include <linux/stat.h>
>> +#ifdef CONFIG_FAIL_MMC_REQUEST
>> +#include <linux/fault-inject.h>
>> +#endif
>
> No #ifdef:ing...
>
I'll remove it.
>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
>> index 0f83858..ee472fe 100644
>> --- a/include/linux/mmc/host.h
>> +++ b/include/linux/mmc/host.h
>> @@ -12,6 +12,9 @@
>>
>> #include <linux/leds.h>
>> #include <linux/sched.h>
>> +#ifdef CONFIG_FAIL_MMC_REQUEST
>> +#include <linux/fault-inject.h>
>> +#endif
>
> Neither here...
>
dito
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index 47879c7..ebff0c9 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>
> I'm contemplating if we should create drivers/mmc/Kconfig.debug
> and stash this in there instead, i.e. also move out MMC_DEBUG
> from drivers/mmc/Kconfig and add to that?
>
> It seems more apropriate to select this from the MMC subsystem.
> However the core of fault injection is in lib/
>
> So maybe a simple:
>
> config FAIL_MMC_REQUEST
> bool
> select FAULT_INJECTION
>
> That can then be selected by a debug option in the MMC subsystem?
> I fear it may be hard to find this otherwise...
>
> (NB: I have very little clue how the Kconfig.debug files get sourced
> into the Kbuild so I might be misguided...)
>
The FAIL_MMC_REQUEST sits right next to the rest of the fail injection
functions.
config FAILSLAB
depends on FAULT_INJECTION
depends on SLAB || SLUB
config FAIL_PAGE_ALLOC
depends on FAULT_INJECTION
config FAIL_MAKE_REQUEST
depends on FAULT_INJECTION && BLOCK
config FAIL_IO_TIMEOUT
depends on FAULT_INJECTION && BLOCK
config FAIL_MMC_REQUEST
select DEBUG_FS
depends on FAULT_INJECTION && MMC
I think the proper place is to have it here together with the rest.
>> @@ -1090,6 +1090,17 @@ 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 && MMC
>
> Isn't:
>
> depends on MMC
> select FAULT_INJECTION
>
> Simpler to use? Now you have to select fault injection first
> to even see this option right?
>
In menuconfig you have to select FAULT_INJECTION first, then you can
choose from a list of available fault injection options. I don't see
any real reason for treating FAIL_MMC_REQUEST different from the rest.
Thanks for your comments.
/Per
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