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Michal Hocko

2018-Apr-24 17:38 UTC

[PATCH v3] kvmalloc: always use vmalloc if CONFIG_DEBUG_SG

On Tue 24-04-18 13:28:49, Mikulas Patocka wrote:> 
> 
> On Tue, 24 Apr 2018, Michal Hocko wrote:
> 
> > On Tue 24-04-18 13:00:11, Mikulas Patocka wrote:
> > > 
> > > 
> > > On Tue, 24 Apr 2018, Michal Hocko wrote:
> > > 
> > > > On Tue 24-04-18 11:50:30, Mikulas Patocka wrote:
> > > > > 
> > > > > 
> > > > > On Tue, 24 Apr 2018, Michal Hocko wrote:
> > > > > 
> > > > > > On Mon 23-04-18 20:06:16, Mikulas Patocka wrote:
> > > > > > [...]
> > > > > > > @@ -404,6 +405,12 @@ void
*kvmalloc_node(size_t size, gfp_t f
> > > > > > >  	 */
> > > > > > >  	WARN_ON_ONCE((flags & GFP_KERNEL) !=
GFP_KERNEL);
> > > > > > >  
> > > > > > > +#ifdef CONFIG_DEBUG_SG
> > > > > > > +	/* Catch bugs when the caller uses DMA API
on the result of kvmalloc. */
> > > > > > > +	if (!(prandom_u32_max(2) & 1))
> > > > > > > +		goto do_vmalloc;
> > > > > > > +#endif
> > > > > > 
> > > > > > I really do not think there is anything DEBUG_SG
specific here. Why you
> > > > > > simply do not follow should_failslab path or even
reuse the function?
> > > > > 
> > > > > CONFIG_DEBUG_SG is enabled by default in RHEL and
Fedora debug kernel (if
> > > > > you don't like CONFIG_DEBUG_SG, pick any other
option that is enabled
> > > > > there).
> > > > 
> > > > Are you telling me that you are shaping a debugging
functionality basing
> > > > on what RHEL has enabled? And you call me evil. This is just
rediculous.
> > > > 
> > > > > Fail-injection framework is if off by default and it
must be explicitly
> > > > > enabled and configured by the user - and most users
won't enable it.
> > > > 
> > > > It can be enabled easily. And if you care enough for your
debugging
> > > > kernel then just make it enabled unconditionally.
> > > 
> > > So, should we add a new option CONFIG_KVMALLOC_FALLBACK_DEFAULT?
I'm not
> > > quite sure if 3 lines of debugging code need an extra option, but
if you
> > > don't want to reuse any existing debug option, it may be
possible. Adding
> > > it to the RHEL debug kernel would be trivial.
> > 
> > Wouldn't it be equally trivial to simply enable the fault
injection? You
> > would get additional failure paths testing as a bonus.
> 
> The RHEL and Fedora debugging kernels are compiled with fault injection. 
> But the fault-injection framework will do nothing unless it is enabled by 
> a kernel parameter or debugfs write.
> 
> Most users don't know about the fault injection kernel parameters or 
> debugfs files and won't enabled it. We need a CONFIG_ option to enable
it
> by default in the debugging kernels (and we could add a kernel parameter 
> to override the default, fine-tune the fallback probability etc.)
If it is a real issue to install the debugging kernel with the required
kernel parameter then I a config option for the default on makes sense
to me.
-- 
Michal Hocko
SUSE Labs

Mikulas Patocka

2018-Apr-25 20:02 UTC

head link

[PATCH] fault-injection: reorder config entries

This patch reorders Kconfig entries, so that menuconfig displays proper 
indentation.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>

---
 lib/Kconfig.debug |   36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

Index: linux-2.6/lib/Kconfig.debug
==================================================================---
linux-2.6.orig/lib/Kconfig.debug	2018-04-16 21:08:36.000000000 +0200
+++ linux-2.6/lib/Kconfig.debug	2018-04-25 15:56:16.000000000 +0200
@@ -1503,6 +1503,10 @@ config NETDEV_NOTIFIER_ERROR_INJECT
 
 	  If unsure, say N.
 
+config FUNCTION_ERROR_INJECTION
+	def_bool y
+	depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
+
 config FAULT_INJECTION
 	bool "Fault-injection framework"
 	depends on DEBUG_KERNEL
@@ -1510,10 +1514,6 @@ config FAULT_INJECTION
 	  Provide fault-injection framework.
 	  For more details, see Documentation/fault-injection/.
 
-config FUNCTION_ERROR_INJECTION
-	def_bool y
-	depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
-
 config FAILSLAB
 	bool "Fault-injection capability for kmalloc"
 	depends on FAULT_INJECTION
@@ -1544,16 +1544,6 @@ 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"
-	depends on FAULT_INJECTION_DEBUG_FS && MMC
-	help
-	  Provide fault-injection capability for MMC IO.
-	  This will make the mmc core return data errors. This is
-	  useful to test the error handling in the mmc block device
-	  and to test how the mmc host driver handles retries from
-	  the block device.
-
 config FAIL_FUTEX
 	bool "Fault-injection capability for futexes"
 	select DEBUG_FS
@@ -1561,6 +1551,12 @@ config FAIL_FUTEX
 	help
 	  Provide fault-injection capability for futexes.
 
+config FAULT_INJECTION_DEBUG_FS
+	bool "Debugfs entries for fault-injection capabilities"
+	depends on FAULT_INJECTION && SYSFS && DEBUG_FS
+	help
+	  Enable configuration of fault-injection capabilities via debugfs.
+
 config FAIL_FUNCTION
 	bool "Fault-injection capability for functions"
 	depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
@@ -1571,11 +1567,15 @@ config FAIL_FUNCTION
 	  an error value and have to handle it. This is useful to test the
 	  error handling in various subsystems.
 
-config FAULT_INJECTION_DEBUG_FS
-	bool "Debugfs entries for fault-injection capabilities"
-	depends on FAULT_INJECTION && SYSFS && DEBUG_FS
+config FAIL_MMC_REQUEST
+	bool "Fault-injection capability for MMC IO"
+	depends on FAULT_INJECTION_DEBUG_FS && MMC
 	help
-	  Enable configuration of fault-injection capabilities via debugfs.
+	  Provide fault-injection capability for MMC IO.
+	  This will make the mmc core return data errors. This is
+	  useful to test the error handling in the mmc block device
+	  and to test how the mmc host driver handles retries from
+	  the block device.
 
 config FAULT_INJECTION_STACKTRACE_FILTER
 	bool "stacktrace filter for fault-injection capabilities"

Mikulas Patocka

2018-Apr-25 20:02 UTC

head link

[PATCH v4] fault-injection: introduce kvmalloc fallback options

On Tue, 24 Apr 2018, Michal Hocko wrote:
> > > Wouldn't it be equally trivial to simply enable the fault
injection? You
> > > would get additional failure paths testing as a bonus.
> > 
> > The RHEL and Fedora debugging kernels are compiled with fault
injection.
> > But the fault-injection framework will do nothing unless it is enabled
by
> > a kernel parameter or debugfs write.
> > 
> > Most users don't know about the fault injection kernel parameters
or
> > debugfs files and won't enabled it. We need a CONFIG_ option to
enable it
> > by default in the debugging kernels (and we could add a kernel
parameter
> > to override the default, fine-tune the fallback probability etc.)
> 
> If it is a real issue to install the debugging kernel with the required
> kernel parameter then I a config option for the default on makes sense
> to me.
Yes - the debug kernels use the same default kernel parameters as 
non-debug kernels and it is expected that all debug features are enabled 
by default.

Here I'm sending the patch using the fault-injection framework and the new 
option CONFIG_FAIL_KVMALLOC_FALLBACK_PROBABILITY.

Mikulas



From: Mikulas Patocka <mpatocka at redhat.com>
Subject: [PATCH v4] fault-injection: introduce kvmalloc fallback options

This patch introduces a fault-injection option "kvmalloc_fallback".
This
option makes kvmalloc randomly fall back to vmalloc.

Unfortunatelly, some kernel code has bugs - it uses kvmalloc and then
uses DMA-API on the returned memory or frees it with kfree. Such bugs were
found in the virtio-net driver, dm-integrity or RHEL7 powerpc-specific
code. This options helps to test for these bugs.

The patch introduces a config option FAIL_KVMALLOC_FALLBACK_PROBABILITY.
It can be enabled in distribution debug kernels, so that kvmalloc abuse
can be tested by the users. The default can be overriden with
"kvmalloc_fallback" parameter or in
/sys/kernel/debug/kvmalloc_fallback/.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>

---
 Documentation/fault-injection/fault-injection.txt |    7 +++++
 include/linux/fault-inject.h                      |    9 +++---
 kernel/futex.c                                    |    2 -
 lib/Kconfig.debug                                 |   15 +++++++++++
 mm/failslab.c                                     |    2 -
 mm/page_alloc.c                                   |    2 -
 mm/util.c                                         |   30 ++++++++++++++++++++++
 7 files changed, 60 insertions(+), 7 deletions(-)

Index: linux-2.6/Documentation/fault-injection/fault-injection.txt
==================================================================---
linux-2.6.orig/Documentation/fault-injection/fault-injection.txt	2018-04-16
21:08:34.000000000 +0200
+++ linux-2.6/Documentation/fault-injection/fault-injection.txt	2018-04-25
21:36:36.000000000 +0200
@@ -15,6 +15,12 @@ o fail_page_alloc
 
   injects page allocation failures. (alloc_pages(), get_free_pages(), ...)
 
+o kvmalloc_faillback
+
+  makes the function kvmalloc randonly fall back to vmalloc. This could be used
+  to detects bugs such as using DMA-API on the result of kvmalloc or freeing
+  the result of kvmalloc with free.
+
 o fail_futex
 
   injects futex deadlock and uaddr fault errors.
@@ -167,6 +173,7 @@ use the boot option:
 
 	failslab 	fail_page_alloc+	kvmalloc_faillback 	fail_make_request 	fail_futex 
mmc_core.fail_request=<interval>,<probability>,<space>,<times>
Index: linux-2.6/include/linux/fault-inject.h
==================================================================---
linux-2.6.orig/include/linux/fault-inject.h	2018-04-16 21:08:36.000000000 +0200
+++ linux-2.6/include/linux/fault-inject.h	2018-04-25 21:38:22.000000000 +0200
@@ -31,17 +31,18 @@ struct fault_attr {
 	struct dentry *dname;
 };
 
-#define FAULT_ATTR_INITIALIZER {					\
+#define FAULT_ATTR_INITIALIZER(p) {					\
+		.probability = (p),					\
 		.interval = 1,						\
-		.times = ATOMIC_INIT(1),				\
+		.times = ATOMIC_INIT((p) ? -1 : 1),			\
+		.verbose = (p) ? 0 : 2,					\
 		.require_end = ULONG_MAX,				\
 		.stacktrace_depth = 32,					\
 		.ratelimit_state = RATELIMIT_STATE_INIT_DISABLED,	\
-		.verbose = 2,						\
 		.dname = NULL,						\
 	}
 
-#define DECLARE_FAULT_ATTR(name) struct fault_attr name =
FAULT_ATTR_INITIALIZER
+#define DECLARE_FAULT_ATTR(name) struct fault_attr name =
FAULT_ATTR_INITIALIZER(0)
 int setup_fault_attr(struct fault_attr *attr, char *str);
 bool should_fail(struct fault_attr *attr, ssize_t size);
 
Index: linux-2.6/lib/Kconfig.debug
==================================================================---
linux-2.6.orig/lib/Kconfig.debug	2018-04-25 15:56:16.000000000 +0200
+++ linux-2.6/lib/Kconfig.debug	2018-04-25 21:39:45.000000000 +0200
@@ -1527,6 +1527,21 @@ config FAIL_PAGE_ALLOC
 	help
 	  Provide fault-injection capability for alloc_pages().
 
+config FAIL_KVMALLOC_FALLBACK_PROBABILITY
+	int "Default kvmalloc fallback probability"
+	depends on FAULT_INJECTION
+	range 0 100
+	default "0"
+	help
+	  This option will make kvmalloc randomly fall back to vmalloc.
+	  Normally, kvmalloc falls back to vmalloc only rarely, if memory
+	  is fragmented.
+
+	  This option helps to detect hard-to-reproduce driver bugs, for
+	  example using DMA API on the result of kvmalloc.
+
+	  The default may be overriden with the kvmalloc_faillback parameter.
+
 config FAIL_MAKE_REQUEST
 	bool "Fault-injection capability for disk IO"
 	depends on FAULT_INJECTION && BLOCK
Index: linux-2.6/mm/util.c
==================================================================---
linux-2.6.orig/mm/util.c	2018-04-25 15:48:39.000000000 +0200
+++ linux-2.6/mm/util.c	2018-04-25 21:43:31.000000000 +0200
@@ -14,6 +14,7 @@
 #include <linux/hugetlb.h>
 #include <linux/vmalloc.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/fault-inject.h>
 
 #include <asm/sections.h>
 #include <linux/uaccess.h>
@@ -377,6 +378,29 @@ unsigned long vm_mmap(struct file *file,
 }
 EXPORT_SYMBOL(vm_mmap);
 
+#ifdef CONFIG_FAULT_INJECTION
+
+static struct fault_attr kvmalloc_fallback +
FAULT_ATTR_INITIALIZER(CONFIG_FAIL_KVMALLOC_FALLBACK_PROBABILITY);
+
+static int __init setup_kvmalloc_fallback(char *str)
+{
+	return setup_fault_attr(&kvmalloc_fallback, str);
+}
+
+__setup("kvmalloc_fallback=", setup_kvmalloc_fallback);
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+static int __init kvmalloc_fallback_debugfs_init(void)
+{
+	fault_create_debugfs_attr("kvmalloc_fallback", NULL,
&kvmalloc_fallback);
+	return 0;
+}
+late_initcall(kvmalloc_fallback_debugfs_init);
+#endif
+
+#endif
+
 /**
  * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
  * failure, fall back to non-contiguous (vmalloc) allocation.
@@ -404,6 +428,11 @@ void *kvmalloc_node(size_t size, gfp_t f
 	 */
 	WARN_ON_ONCE((flags & GFP_KERNEL) != GFP_KERNEL);
 
+#ifdef CONFIG_FAULT_INJECTION
+	if (should_fail(&kvmalloc_fallback, size))
+		goto do_vmalloc;
+#endif
+
 	/*
 	 * We want to attempt a large physically contiguous block first because
 	 * it is less likely to fragment multiple larger blocks and therefore
@@ -427,6 +456,7 @@ void *kvmalloc_node(size_t size, gfp_t f
 	if (ret || size <= PAGE_SIZE)
 		return ret;
 
+do_vmalloc: __maybe_unused
 	return __vmalloc_node_flags_caller(size, node, flags,
 			__builtin_return_address(0));
 }
Index: linux-2.6/kernel/futex.c
==================================================================---
linux-2.6.orig/kernel/futex.c	2018-02-14 20:24:42.000000000 +0100
+++ linux-2.6/kernel/futex.c	2018-04-25 21:11:33.000000000 +0200
@@ -288,7 +288,7 @@ static struct {
 
 	bool ignore_private;
 } fail_futex = {
-	.attr = FAULT_ATTR_INITIALIZER,
+	.attr = FAULT_ATTR_INITIALIZER(0),
 	.ignore_private = false,
 };
 
Index: linux-2.6/mm/failslab.c
==================================================================---
linux-2.6.orig/mm/failslab.c	2018-04-16 21:08:36.000000000 +0200
+++ linux-2.6/mm/failslab.c	2018-04-25 21:11:40.000000000 +0200
@@ -9,7 +9,7 @@ static struct {
 	bool ignore_gfp_reclaim;
 	bool cache_filter;
 } failslab = {
-	.attr = FAULT_ATTR_INITIALIZER,
+	.attr = FAULT_ATTR_INITIALIZER(0),
 	.ignore_gfp_reclaim = true,
 	.cache_filter = false,
 };
Index: linux-2.6/mm/page_alloc.c
==================================================================---
linux-2.6.orig/mm/page_alloc.c	2018-04-16 21:08:36.000000000 +0200
+++ linux-2.6/mm/page_alloc.c	2018-04-25 21:11:47.000000000 +0200
@@ -3055,7 +3055,7 @@ static struct {
 	bool ignore_gfp_reclaim;
 	u32 min_order;
 } fail_page_alloc = {
-	.attr = FAULT_ATTR_INITIALIZER,
+	.attr = FAULT_ATTR_INITIALIZER(0),
 	.ignore_gfp_reclaim = true,
 	.ignore_gfp_highmem = true,
 	.min_order = 1,

Randy Dunlap

2018-Apr-25 20:20 UTC

head link

[PATCH v4] fault-injection: introduce kvmalloc fallback options

On 04/25/2018 01:02 PM, Mikulas Patocka wrote:> 
> 
> From: Mikulas Patocka <mpatocka at redhat.com>
> Subject: [PATCH v4] fault-injection: introduce kvmalloc fallback options
> 
> This patch introduces a fault-injection option
"kvmalloc_fallback". This
> option makes kvmalloc randomly fall back to vmalloc.
> 
> Unfortunatelly, some kernel code has bugs - it uses kvmalloc and then
  Unfortunately,
> uses DMA-API on the returned memory or frees it with kfree. Such bugs were
> found in the virtio-net driver, dm-integrity or RHEL7 powerpc-specific
> code. This options helps to test for these bugs.
> 
> The patch introduces a config option FAIL_KVMALLOC_FALLBACK_PROBABILITY.
> It can be enabled in distribution debug kernels, so that kvmalloc abuse
> can be tested by the users. The default can be overriden with
                                                 overridden
> "kvmalloc_fallback" parameter or in
/sys/kernel/debug/kvmalloc_fallback/.
> 
> Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
> 
> ---
>  Documentation/fault-injection/fault-injection.txt |    7 +++++
>  include/linux/fault-inject.h                      |    9 +++---
>  kernel/futex.c                                    |    2 -
>  lib/Kconfig.debug                                 |   15 +++++++++++
>  mm/failslab.c                                     |    2 -
>  mm/page_alloc.c                                   |    2 -
>  mm/util.c                                         |   30
++++++++++++++++++++++
>  7 files changed, 60 insertions(+), 7 deletions(-)
> 
> Index: linux-2.6/Documentation/fault-injection/fault-injection.txt
> ==================================================================> ---
linux-2.6.orig/Documentation/fault-injection/fault-injection.txt	2018-04-16
21:08:34.000000000 +0200
> +++ linux-2.6/Documentation/fault-injection/fault-injection.txt	2018-04-25
21:36:36.000000000 +0200
> @@ -15,6 +15,12 @@ o fail_page_alloc
>  
>    injects page allocation failures. (alloc_pages(), get_free_pages(), ...)
>  
> +o kvmalloc_faillback
     kvmalloc_fallback
> +
> +  makes the function kvmalloc randonly fall back to vmalloc. This could be
used
                                 randomly
> +  to detects bugs such as using DMA-API on the result of kvmalloc or
freeing
> +  the result of kvmalloc with free.
> +
>  o fail_futex
>  
>    injects futex deadlock and uaddr fault errors.
> @@ -167,6 +173,7 @@ use the boot option:
>  
>  	failslab>  	fail_page_alloc> +	kvmalloc_faillback
	kvmalloc_fallback>  	fail_make_request>  	fail_futex>  
mmc_core.fail_request=<interval>,<probability>,<space>,<times>
> Index: linux-2.6/lib/Kconfig.debug
> ==================================================================> ---
linux-2.6.orig/lib/Kconfig.debug	2018-04-25 15:56:16.000000000 +0200
> +++ linux-2.6/lib/Kconfig.debug	2018-04-25 21:39:45.000000000 +0200
> @@ -1527,6 +1527,21 @@ config FAIL_PAGE_ALLOC
>  	help
>  	  Provide fault-injection capability for alloc_pages().
>  
> +config FAIL_KVMALLOC_FALLBACK_PROBABILITY
> +	int "Default kvmalloc fallback probability"
> +	depends on FAULT_INJECTION
> +	range 0 100
> +	default "0"
> +	help
> +	  This option will make kvmalloc randomly fall back to vmalloc.
> +	  Normally, kvmalloc falls back to vmalloc only rarely, if memory
> +	  is fragmented.
> +
> +	  This option helps to detect hard-to-reproduce driver bugs, for
> +	  example using DMA API on the result of kvmalloc.
> +
> +	  The default may be overriden with the kvmalloc_faillback parameter.
	                     overridden         kvmalloc_fallback
> +
>  config FAIL_MAKE_REQUEST
>  	bool "Fault-injection capability for disk IO"
>  	depends on FAULT_INJECTION && BLOCK
-- 
~Randy

Randy Dunlap

2018-Apr-26 03:21 UTC

head link

[PATCH] fault-injection: reorder config entries

On 04/25/2018 01:02 PM, Mikulas Patocka wrote:> This patch reorders Kconfig entries, so that menuconfig displays proper 
> indentation.
> 
> Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
Acked-by: Randy Dunlap <rdunlap at infradead.org>
Tested-by: Randy Dunlap <rdunlap at infradead.org>

Thanks.
> ---
>  lib/Kconfig.debug |   36 ++++++++++++++++++------------------
>  1 file changed, 18 insertions(+), 18 deletions(-)
> 
> Index: linux-2.6/lib/Kconfig.debug
> ==================================================================> ---
linux-2.6.orig/lib/Kconfig.debug	2018-04-16 21:08:36.000000000 +0200
> +++ linux-2.6/lib/Kconfig.debug	2018-04-25 15:56:16.000000000 +0200
> @@ -1503,6 +1503,10 @@ config NETDEV_NOTIFIER_ERROR_INJECT
>  
>  	  If unsure, say N.
>  
> +config FUNCTION_ERROR_INJECTION
> +	def_bool y
> +	depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
> +
>  config FAULT_INJECTION
>  	bool "Fault-injection framework"
>  	depends on DEBUG_KERNEL
> @@ -1510,10 +1514,6 @@ config FAULT_INJECTION
>  	  Provide fault-injection framework.
>  	  For more details, see Documentation/fault-injection/.
>  
> -config FUNCTION_ERROR_INJECTION
> -	def_bool y
> -	depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
> -
>  config FAILSLAB
>  	bool "Fault-injection capability for kmalloc"
>  	depends on FAULT_INJECTION
> @@ -1544,16 +1544,6 @@ 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"
> -	depends on FAULT_INJECTION_DEBUG_FS && MMC
> -	help
> -	  Provide fault-injection capability for MMC IO.
> -	  This will make the mmc core return data errors. This is
> -	  useful to test the error handling in the mmc block device
> -	  and to test how the mmc host driver handles retries from
> -	  the block device.
> -
>  config FAIL_FUTEX
>  	bool "Fault-injection capability for futexes"
>  	select DEBUG_FS
> @@ -1561,6 +1551,12 @@ config FAIL_FUTEX
>  	help
>  	  Provide fault-injection capability for futexes.
>  
> +config FAULT_INJECTION_DEBUG_FS
> +	bool "Debugfs entries for fault-injection capabilities"
> +	depends on FAULT_INJECTION && SYSFS && DEBUG_FS
> +	help
> +	  Enable configuration of fault-injection capabilities via debugfs.
> +
>  config FAIL_FUNCTION
>  	bool "Fault-injection capability for functions"
>  	depends on FAULT_INJECTION_DEBUG_FS && FUNCTION_ERROR_INJECTION
> @@ -1571,11 +1567,15 @@ config FAIL_FUNCTION
>  	  an error value and have to handle it. This is useful to test the
>  	  error handling in various subsystems.
>  
> -config FAULT_INJECTION_DEBUG_FS
> -	bool "Debugfs entries for fault-injection capabilities"
> -	depends on FAULT_INJECTION && SYSFS && DEBUG_FS
> +config FAIL_MMC_REQUEST
> +	bool "Fault-injection capability for MMC IO"
> +	depends on FAULT_INJECTION_DEBUG_FS && MMC
>  	help
> -	  Enable configuration of fault-injection capabilities via debugfs.
> +	  Provide fault-injection capability for MMC IO.
> +	  This will make the mmc core return data errors. This is
> +	  useful to test the error handling in the mmc block device
> +	  and to test how the mmc host driver handles retries from
> +	  the block device.
>  
>  config FAULT_INJECTION_STACKTRACE_FILTER
>  	bool "stacktrace filter for fault-injection capabilities"
> 

-- 
~Randy

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