linux-kernel - Re: [PATCH v2 1/2] fault-inject: Restore support for task-independent fault injection

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Date:   Wed, 23 Aug 2017 07:59:30 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Akinobu Mita <akinobu.mita@...il.com>
Cc:     Bart Van Assche <bart.vanassche@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-block@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH v2 1/2] fault-inject: Restore support for task-independent
 fault injection

On Wed, Aug 23, 2017 at 2:10 AM, Akinobu Mita <akinobu.mita@...il.com> wrote:
> 2017-08-23 8:00 GMT+09:00 Bart Van Assche <bart.vanassche@....com>:
>> Certain faults should be injected independent of the context
>> in which these occur. Commit e41d58185f14 made it impossible to
>> inject faults independent of their context. Restore support for
>> task-independent fault injection by adding the attribute 'global'.
>
> There was a the problem reported by fail-make-request user and the
> problem is introduced by the follow-up patches for systematic
> fault injection.
>
> Please check the commit 9eeb52ae712e ("fault-inject: fix wrong
> should_fail() decision in task context") and see if the problem
> you reported is identical to the commit.

Agree.
Otherwise I don't understand this commit. We now have 2 orthogonal
injection mechanisms: one global (original) and the new local. If one
needs global injection, he/she just enables the global one. We don't
seem to need the global flag on fault attributes.



>> References: commit e41d58185f14 ("fault-inject: support systematic fault injection")
>> Signed-off-by: Bart Van Assche <bart.vanassche@....com>
>> Cc: Dmitry Vyukov <dvyukov@...gle.com>
>> Cc: Akinobu Mita <akinobu.mita@...il.com>
>> Cc: Michal Hocko <mhocko@...nel.org>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> ---
>>  include/linux/fault-inject.h | 11 +++++++++--
>>  lib/fault-inject.c           |  4 +++-
>>  2 files changed, 12 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h
>> index 728d4e0292aa..88dae2f21881 100644
>> --- a/include/linux/fault-inject.h
>> +++ b/include/linux/fault-inject.h
>> @@ -18,6 +18,7 @@ struct fault_attr {
>>         atomic_t times;
>>         atomic_t space;
>>         unsigned long verbose;
>> +       bool global;
>>         bool task_filter;
>>         unsigned long stacktrace_depth;
>>         unsigned long require_start;
>> @@ -30,17 +31,23 @@ struct fault_attr {
>>         struct dentry *dname;
>>  };
>>
>> -#define FAULT_ATTR_INITIALIZER {                                       \
>> +#define __FAULT_ATTR_INITIALIZER(__global) {                           \
>>                 .interval = 1,                                          \
>>                 .times = ATOMIC_INIT(1),                                \
>>                 .require_end = ULONG_MAX,                               \
>> +               .global = (__global),                                   \
>>                 .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 FAULT_ATTR_INITIALIZER __FAULT_ATTR_INITIALIZER(false)
>> +
>> +#define DECLARE_FAULT_ATTR(name)                               \
>> +       struct fault_attr name = __FAULT_ATTR_INITIALIZER(false)
>> +#define DECLARE_GLOBAL_FAULT_ATTR(name)                                \
>> +       struct fault_attr name = __FAULT_ATTR_INITIALIZER(true)
>>  int setup_fault_attr(struct fault_attr *attr, char *str);
>>  bool should_fail(struct fault_attr *attr, ssize_t size);
>>
>> diff --git a/lib/fault-inject.c b/lib/fault-inject.c
>> index 7d315fdb9f13..c8f6ef5df3c6 100644
>> --- a/lib/fault-inject.c
>> +++ b/lib/fault-inject.c
>> @@ -107,7 +107,7 @@ static inline bool fail_stacktrace(struct fault_attr *attr)
>>
>>  bool should_fail(struct fault_attr *attr, ssize_t size)
>>  {
>> -       if (in_task()) {
>> +       if (!attr->global && in_task()) {
>>                 unsigned int fail_nth = READ_ONCE(current->fail_nth);
>>
>>                 if (fail_nth && !WRITE_ONCE(current->fail_nth, fail_nth - 1))
>> @@ -224,6 +224,8 @@ struct dentry *fault_create_debugfs_attr(const char *name,
>>         if (!debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
>>                                 &attr->ratelimit_state.burst))
>>                 goto fail;
>> +       if (!debugfs_create_bool("global", mode, dir, &attr->global))
>> +               goto fail;
>>         if (!debugfs_create_bool("task-filter", mode, dir, &attr->task_filter))
>>                 goto fail;
>>
>> --
>> 2.14.0
>>