[PATCH 0/2] Make I/O timeout failure injection again task-independent

[PATCH 0/2] Make I/O timeout failure injection again task-independent

[Bart Van Assche]

Hello Andrew,

A recent change in the fault injection code introduced an undesired change
in the behavior of the I/O timeout failure injection code. This series
restores the original behavior. Please consider these patches for kernel
v4.14.

Thanks,

Bart.

Bart Van Assche (2):
  fault-inject: Restore support for task-independent fault injection
  block: Make I/O timeout failure injection support again
    task-independent

 block/blk-timeout.c          | 2 +-
 include/linux/fault-inject.h | 9 +++++++--
 lib/fault-inject.c           | 4 +++-
 3 files changed, 11 insertions(+), 4 deletions(-)

-- 
2.14.0

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

[Bart Van Assche]

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'.

References: commit e41d58185f14 ("fault-inject: support systematic fault injection")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 include/linux/fault-inject.h | 9 +++++++--
 lib/fault-inject.c           | 4 +++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h
index 728d4e0292aa..8851646d2698 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 +31,21 @@ 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 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

[PATCH 2/2] block: Make I/O timeout failure injection support again task-independent

[Bart Van Assche]

Commit e41d58185f14 made all faults that are triggered from task
context, including I/O timeouts, dependent on the failure
injection settings for that task. Make it again possible to inject
I/O timeout failures independent of task context. An example for a
fault injection for which this patch makes a difference (from a VM
booted with the 'threadirqs' command line parameter):

FAULT_INJECTION: forcing a failure. name fail_io_timeout, interval 1, probability 100, space 0, times 1
CPU: 6 PID: 1253 Comm: irq/36-skd0-msi Not tainted 4.13.0-rc2-dbg+ #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc26 04/01/2014
Call Trace:
 dump_stack+0x8e/0xcd
 should_fail+0x154/0x160
 blk_should_fake_timeout+0x27/0x30
 blk_mq_complete_request+0x11/0x30
 skd_end_request+0x32/0xc0 [skd]
 skd_isr_completion_posted.isra.30+0x14a/0x400 [skd]
 skd_comp_q+0x40/0xb0 [skd]
 irq_forced_thread_fn+0x2a/0x70
 irq_thread+0x144/0x1a0
 kthread+0x125/0x140
 ret_from_fork+0x2a/0x40

Fixes: commit e41d58185f14 ("fault-inject: support systematic fault injection")
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 block/blk-timeout.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-timeout.c b/block/blk-timeout.c
index 17ec83bb0900..2e92b20b125f 100644
--- a/block/blk-timeout.c
+++ b/block/blk-timeout.c
@@ -11,7 +11,7 @@
 
 #ifdef CONFIG_FAIL_IO_TIMEOUT
 
-static DECLARE_FAULT_ATTR(fail_io_timeout);
+static DECLARE_GLOBAL_FAULT_ATTR(fail_io_timeout);
 
 static int __init setup_fail_io_timeout(char *str)
 {
-- 
2.14.0