linux-kernel - Re: [PATCH] mmc: add ifdef around fault_create_debugfs

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Message-ID: <20151110160420.2ec59606.adrien+dev@schischi.me>
Date:	Tue, 10 Nov 2015 16:04:20 +0100
From:	Adrien Schildknecht <adrien+dev@...ischi.me>
To:	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	Shawn Lin <shawn.lin@...k-chips.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: add ifdef around fault_create_debugfs_attr()

On Mon, 9 Nov 2015 14:33:11 +0100
Ulf Hansson <ulf.hansson@...aro.org> wrote:
> On 6 November 2015 at 13:15, Adrien Schildknecht
> <adrien+dev@...ischi.me> wrote:  
> > FAIL_MMC_REQUEST can be used without FAULT_INJECTION_DEBUG_FS.
> > In this case fault_create_debugfs_attr() will always return an
> > error and lead to the deletion of the whole debugfs directory.
> >
> > This patch makes sure that FAULT_INJECTION_DEBUG_FS is enabled
> > before attempting to create the debugfs atttribute.
> >
> > Signed-off-by: Adrien Schildknecht <adrien+dev@...ischi.me>
> > ---
> >  drivers/mmc/core/debugfs.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
> > index 154aced..13e842c 100644
> > --- a/drivers/mmc/core/debugfs.c
> > +++ b/drivers/mmc/core/debugfs.c
> > @@ -259,11 +259,13 @@ void mmc_add_host_debugfs(struct mmc_host
> > *host) if (fail_request)
> >                 setup_fault_attr(&fail_default_attr, fail_request);
> >         host->fail_mmc_request = fail_default_attr;
> > +#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
> >         if (IS_ERR(fault_create_debugfs_attr("fail_mmc_request",
> >                                              root,
> >                                              &host->fail_mmc_request)))
> >                 goto err_node;
> >  #endif
> > +#endif
> >         return;
> >
> >  err_node:
> > --
> > 2.6.2
> >    
> 
> I think you are solving this in the wrong way. Will it really makes
> sense to use FAIL_MMC_REQUEST unless FAULT_INJECTION_DEBUG_FS is set,
> I don't think so.  
The fault attribute can be configured using either the debugfs or the
module parameter "fail_request". It is thus possible to use
FAIL_MMC_REQUEST without FAULT_INJECTION_DEBUG_FS (even if it is less
convenient).

> I suggest you to change FAIL_MMC_REQUEST from depending on
> FAULT_INJECTION to FAULT_INJECTION_DEBUG_FS in /lib/Kconfig.debug.  
The other systems that use the fault injection infrastructure (futex,
alloc_pages, slab...) can be used without the dependency on
FAULT_INJECTION_DEBUG_FS. They also use nested #ifdef to handle this
configuration. I chose the #ifdef approach for the sake of coherence.

-- 
Adrien Schildknecht
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