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Subject[PATCH 1/2 -mm] fault-injection: safer defaults, trivial optimization, cleanup
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Date
Set /debug/fail*/* defaults supposed most likely to please a new user.
Clamp /debug/fail*/stacktrace-depth to MAX_STACK_TRACE_DEPTH.

In should_fail(), move stack-unwinding test past cheaper tests (performance
gain not quantified). Simplify logic; eliminate goto.
Use bool/true/false consistently.

Correct and disambiguate documentation.

Signed-off-by: Don Mullis <dwm@meer.net>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
---
Documentation/fault-injection/failmodule.sh | 4 -
Documentation/fault-injection/fault-injection.txt | 39 +++++------
include/linux/fault-inject.h | 3
lib/fault-inject.c | 74 +++++++++++++---------
mm/page_alloc.c | 2
mm/slab.c | 1
6 files changed, 71 insertions(+), 52 deletions(-)

Index: linux-2.6.18/mm/slab.c
===================================================================
--- linux-2.6.18.orig/mm/slab.c
+++ linux-2.6.18/mm/slab.c
@@ -3111,6 +3111,7 @@ static struct failslab_attr {

} failslab = {
.attr = FAULT_ATTR_INITIALIZER,
+ .ignore_gfp_wait = 1,
};

static int __init setup_failslab(char *str)
Index: linux-2.6.18/include/linux/fault-inject.h
===================================================================
--- linux-2.6.18.orig/include/linux/fault-inject.h
+++ linux-2.6.18/include/linux/fault-inject.h
@@ -52,12 +52,13 @@ struct fault_attr {
.times = ATOMIC_INIT(1), \
.require_end = ULONG_MAX, \
.stacktrace_depth = 32, \
+ .verbose = 2, \
}

#define DECLARE_FAULT_ATTR(name) struct fault_attr name = FAULT_ATTR_INITIALIZER
int setup_fault_attr(struct fault_attr *attr, char *str);
void should_fail_srandom(unsigned long entropy);
-int should_fail(struct fault_attr *attr, ssize_t size);
+bool should_fail(struct fault_attr *attr, ssize_t size);

#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS

Index: linux-2.6.18/lib/fault-inject.c
===================================================================
--- linux-2.6.18.orig/lib/fault-inject.c
+++ linux-2.6.18/lib/fault-inject.c
@@ -48,11 +48,13 @@ static void fail_dump(struct fault_attr

#define atomic_dec_not_zero(v) atomic_add_unless((v), -1, 0)

-static int fail_task(struct fault_attr *attr, struct task_struct *task)
+static bool fail_task(struct fault_attr *attr, struct task_struct *task)
{
return !in_interrupt() && task->make_it_fail;
}

+#define MAX_STACK_TRACE_DEPTH 32
+
#ifdef CONFIG_STACK_UNWIND

static asmlinkage int fail_stacktrace_callback(struct unwind_frame_info *info,
@@ -68,15 +70,15 @@ static asmlinkage int fail_stacktrace_ca
break;
if (attr->reject_start <= UNW_PC(info) &&
UNW_PC(info) < attr->reject_end)
- return 0;
+ return false;
if (attr->require_start <= UNW_PC(info) &&
UNW_PC(info) < attr->require_end)
- found = 1;
+ found = true;
}
return found;
}

-static int fail_stacktrace(struct fault_attr *attr)
+static bool fail_stacktrace(struct fault_attr *attr)
{
struct unwind_frame_info info;

@@ -85,9 +87,7 @@ static int fail_stacktrace(struct fault_

#elif defined(CONFIG_STACKTRACE)

-#define MAX_STACK_TRACE_DEPTH 32
-
-static int fail_stacktrace(struct fault_attr *attr)
+static bool fail_stacktrace(struct fault_attr *attr)
{
struct stack_trace trace;
int depth = attr->stacktrace_depth;
@@ -100,8 +100,7 @@ static int fail_stacktrace(struct fault_

trace.nr_entries = 0;
trace.entries = entries;
- trace.max_entries = (depth < MAX_STACK_TRACE_DEPTH) ?
- depth : MAX_STACK_TRACE_DEPTH;
+ trace.max_entries = depth;
trace.skip = 1;
trace.all_contexts = 0;

@@ -109,26 +108,26 @@ static int fail_stacktrace(struct fault_
for (n = 0; n < trace.nr_entries; n++) {
if (attr->reject_start <= entries[n] &&
entries[n] < attr->reject_end)
- return 0;
+ return false;
if (attr->require_start <= entries[n] &&
entries[n] < attr->require_end)
- found = 1;
+ found = true;
}
return found;
}

#else

-static inline int fail_stacktrace(struct fault_attr *attr)
+static inline bool fail_stacktrace(struct fault_attr *attr)
{
- static int firsttime = 1;
+ static bool firsttime = true;

if (firsttime) {
printk(KERN_WARNING
"This architecture does not implement save_stack_trace()\n");
- firsttime = 0;
+ firsttime = false;
}
- return 0;
+ return false;
}

#endif
@@ -138,40 +137,37 @@ static inline int fail_stacktrace(struct
* http://www.nongnu.org/failmalloc/
*/

-int should_fail(struct fault_attr *attr, ssize_t size)
+bool should_fail(struct fault_attr *attr, ssize_t size)
{
if (attr->task_filter && !fail_task(attr, current))
- return 0;
-
- if (!fail_stacktrace(attr))
- return 0;
+ return false;

if (atomic_read(&attr->times) == 0)
- return 0;
+ return false;

if (atomic_read(&attr->space) > size) {
atomic_sub(size, &attr->space);
- return 0;
+ return false;
}

if (attr->interval > 1) {
attr->count++;
if (attr->count % attr->interval)
- return 0;
+ return false;
}

- if (attr->probability > random32() % 100)
- goto fail;
+ if (attr->probability <= random32() % 100)
+ return false;

- return 0;
+ if (!fail_stacktrace(attr))
+ return false;

-fail:
fail_dump(attr);

if (atomic_read(&attr->times) != -1)
atomic_dec_not_zero(&attr->times);

- return 1;
+ return true;
}

#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
@@ -181,6 +177,13 @@ static void debugfs_ul_set(void *data, u
*(unsigned long *)data = val;
}

+static void debugfs_ul_set_MAX_STACK_TRACE_DEPTH(void *data, u64 val)
+{
+ *(unsigned long *)data =
+ val < MAX_STACK_TRACE_DEPTH ?
+ val : MAX_STACK_TRACE_DEPTH;
+}
+
static u64 debugfs_ul_get(void *data)
{
return *(unsigned long *)data;
@@ -194,6 +197,17 @@ static struct dentry *debugfs_create_ul(
return debugfs_create_file(name, mode, parent, value, &fops_ul);
}

+DEFINE_SIMPLE_ATTRIBUTE(fops_ul_MAX_STACK_TRACE_DEPTH, debugfs_ul_get,
+ debugfs_ul_set_MAX_STACK_TRACE_DEPTH, "%llu\n");
+
+static struct dentry *debugfs_create_ul_MAX_STACK_TRACE_DEPTH(
+ const char *name, mode_t mode,
+ struct dentry *parent, unsigned long *value)
+{
+ return debugfs_create_file(name, mode, parent, value,
+ &fops_ul_MAX_STACK_TRACE_DEPTH);
+}
+
static void debugfs_atomic_t_set(void *data, u64 val)
{
atomic_set((atomic_t *)data, val);
@@ -286,8 +300,8 @@ int init_fault_attr_dentries(struct faul
mode, dir, &attr->task_filter);

attr->dentries.stacktrace_depth_file =
- debugfs_create_ul("stacktrace-depth", mode, dir,
- &attr->stacktrace_depth);
+ debugfs_create_ul_MAX_STACK_TRACE_DEPTH(
+ "stacktrace-depth", mode, dir, &attr->stacktrace_depth);

attr->dentries.require_start_file =
debugfs_create_ul("require-start", mode, dir, &attr->require_start);
Index: linux-2.6.18/mm/page_alloc.c
===================================================================
--- linux-2.6.18.orig/mm/page_alloc.c
+++ linux-2.6.18/mm/page_alloc.c
@@ -929,6 +929,8 @@ static struct fail_page_alloc_attr {

} fail_page_alloc = {
.attr = FAULT_ATTR_INITIALIZER,
+ .ignore_gfp_wait = 1,
+ .ignore_gfp_highmem = 1,
};

static int __init setup_fail_page_alloc(char *str)
Index: linux-2.6.18/Documentation/fault-injection/failmodule.sh
===================================================================
--- linux-2.6.18.orig/Documentation/fault-injection/failmodule.sh
+++ linux-2.6.18/Documentation/fault-injection/failmodule.sh
@@ -26,6 +26,6 @@ fi
# Disable any fault injection
echo 0 > /debug/$1/stacktrace-depth

-echo `cat /sys/module/$2/sections/.text` > /debug/$1/address-start
-echo `cat /sys/module/$2/sections/.exit.text` > /debug/$1/address-end
+echo `cat /sys/module/$2/sections/.text` > /debug/$1/require-start
+echo `cat /sys/module/$2/sections/.exit.text` > /debug/$1/require-end
echo $STACKTRACE_DEPTH > /debug/$1/stacktrace-depth
Index: linux-2.6.18/Documentation/fault-injection/fault-injection.txt
===================================================================
--- linux-2.6.18.orig/Documentation/fault-injection/fault-injection.txt
+++ linux-2.6.18/Documentation/fault-injection/fault-injection.txt
@@ -29,16 +29,16 @@ o debugfs entries
fault-inject-debugfs kernel module provides some debugfs entries for runtime
configuration of fault-injection capabilities.

-- /debug/*/probability:
+- /debug/fail*/probability:

likelihood of failure injection, in percent.
Format: <percent>

Note that one-failure-per-handred is a very high error rate
for some testcases. Please set probably=100 and configure
- /debug/*/interval for such testcases.
+ /debug/fail*/interval for such testcases.

-- /debug/*/interval:
+- /debug/fail*/interval:

specifies the interval between failures, for calls to
should_fail() that pass all the other tests.
@@ -46,18 +46,18 @@ configuration of fault-injection capabil
Note that if you enable this, by setting interval>1, you will
probably want to set probability=100.

-- /debug/*/times:
+- /debug/fail*/times:

specifies how many times failures may happen at most.
A value of -1 means "no limit".

-- /debug/*/space:
+- /debug/fail*/space:

specifies an initial resource "budget", decremented by "size"
on each call to should_fail(,size). Failure injection is
suppressed until "space" reaches zero.

-- /debug/*/verbose
+- /debug/fail*/verbose

Format: { 0 | 1 | 2 }
specifies the verbosity of the messages when failure is injected.
@@ -66,17 +66,17 @@ configuration of fault-injection capabil
it is useful to debug the problems revealed by fault injection
capabilities.

-- /debug/*/task-filter:
+- /debug/fail*/task-filter:

- Format: { 0 | 1 }
- A value of '0' disables filtering by process (default).
+ Format: { 'Y' | 'N' }
+ A value of 'N' disables filtering by process (default).
Any positive value limits failures to only processes indicated by
/proc/<pid>/make-it-fail==1.

-- /debug/*/require-start:
-- /debug/*/require-end:
-- /debug/*/reject-start:
-- /debug/*/reject-end:
+- /debug/fail*/require-start:
+- /debug/fail*/require-end:
+- /debug/fail*/reject-start:
+- /debug/fail*/reject-end:

specifies the range of virtual addresses tested during
stacktrace walking. Failure is injected only if some caller
@@ -85,22 +85,23 @@ configuration of fault-injection capabil
Default required range is [0,ULONG_MAX) (whole of virtual address space).
Default rejected range is [0,0).

-- /debug/*/stacktrace-depth:
+- /debug/fail*/stacktrace-depth:

specifies the maximum stacktrace depth walked during search
- for a caller within [address-start,address-end).
+ for a caller within [require-start,require-end) OR
+ [reject-start,reject-end).

- /debug/fail_page_alloc/ignore-gfp-highmem:

- Format: { 0 | 1 }
- default is 0, setting it to '1' won't inject failures into
+ Format: { 'Y' | 'N' }
+ default is 'N', setting it to 'Y' won't inject failures into
highmem/user allocations.

- /debug/failslab/ignore-gfp-wait:
- /debug/fail_page_alloc/ignore-gfp-wait:

- Format: { 0 | 1 }
- default is 0, setting it to '1' will inject failures
+ Format: { 'Y' | 'N' }
+ default is 'N', setting it to 'Y' will inject failures
only into non-sleep allocations (GFP_ATOMIC allocations).

o Boot option

-
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