Documentation: nvme: Documentation for nvme fault injection

Add examples to show how to use nvme fault injection.
Signed-off-by: Thomas Tai <thomas.tai@oracle.com>
Reviewed-by: Eric Saint-Etienne <eric.saint.etienne@oracle.com>
Signed-off-by: Karl Volz <karl.volz@oracle.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Documentation/fault-injection/fault-injection.txt

@@ -36,6 +36,14 @@ o fail_function
   ALLOW_ERROR_INJECTION() macro, by setting debugfs entries
   under /sys/kernel/debug/fail_function. No boot option supported.
 
+o NVMe fault injection
+
+  inject NVMe status code and retry flag on devices permitted by setting
+  debugfs entries under /sys/kernel/debug/nvme*/fault_inject. The default
+  status code is NVME_SC_INVALID_OPCODE with no retry. The status code and
+  retry flag can be set via the debugfs.
+
+
 Configure fault-injection capabilities behavior
 -----------------------------------------------
 

Documentation/fault-injection/nvme-fault-injection.txt

+NVMe Fault Injection
+====================
+Linux's fault injection framework provides a systematic way to support
+error injection via debugfs in the /sys/kernel/debug directory. When
+enabled, the default NVME_SC_INVALID_OPCODE with no retry will be
+injected into the nvme_end_request. Users can change the default status
+code and no retry flag via the debugfs. The list of Generic Command
+Status can be found in include/linux/nvme.h
+
+Following examples show how to inject an error into the nvme.
+
+First, enable CONFIG_FAULT_INJECTION_DEBUG_FS kernel config,
+recompile the kernel. After booting up the kernel, do the
+following.
+
+Example 1: Inject default status code with no retry
+---------------------------------------------------
+
+mount /dev/nvme0n1 /mnt
+echo 1 > /sys/kernel/debug/nvme0n1/fault_inject/times
+echo 100 > /sys/kernel/debug/nvme0n1/fault_inject/probability
+cp a.file /mnt
+
+Expected Result:
+
+cp: cannot stat ‘/mnt/a.file’: Input/output error
+
+Message from dmesg:
+
+FAULT_INJECTION: forcing a failure.
+name fault_inject, interval 1, probability 100, space 0, times 1
+CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc8+ #2
+Hardware name: innotek GmbH VirtualBox/VirtualBox,
+BIOS VirtualBox 12/01/2006
+Call Trace:
+  <IRQ>
+  dump_stack+0x5c/0x7d
+  should_fail+0x148/0x170
+  nvme_should_fail+0x2f/0x50 [nvme_core]
+  nvme_process_cq+0xe7/0x1d0 [nvme]
+  nvme_irq+0x1e/0x40 [nvme]
+  __handle_irq_event_percpu+0x3a/0x190
+  handle_irq_event_percpu+0x30/0x70
+  handle_irq_event+0x36/0x60
+  handle_fasteoi_irq+0x78/0x120
+  handle_irq+0xa7/0x130
+  ? tick_irq_enter+0xa8/0xc0
+  do_IRQ+0x43/0xc0
+  common_interrupt+0xa2/0xa2
+  </IRQ>
+RIP: 0010:native_safe_halt+0x2/0x10
+RSP: 0018:ffffffff82003e90 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffdd
+RAX: ffffffff817a10c0 RBX: ffffffff82012480 RCX: 0000000000000000
+RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
+RBP: 0000000000000000 R08: 000000008e38ce64 R09: 0000000000000000
+R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff82012480
+R13: ffffffff82012480 R14: 0000000000000000 R15: 0000000000000000
+  ? __sched_text_end+0x4/0x4
+  default_idle+0x18/0xf0
+  do_idle+0x150/0x1d0
+  cpu_startup_entry+0x6f/0x80
+  start_kernel+0x4c4/0x4e4
+  ? set_init_arg+0x55/0x55
+  secondary_startup_64+0xa5/0xb0
+  print_req_error: I/O error, dev nvme0n1, sector 9240
+EXT4-fs error (device nvme0n1): ext4_find_entry:1436:
+inode #2: comm cp: reading directory lblock 0
+
+Example 2: Inject default status code with retry
+------------------------------------------------
+
+mount /dev/nvme0n1 /mnt
+echo 1 > /sys/kernel/debug/nvme0n1/fault_inject/times
+echo 100 > /sys/kernel/debug/nvme0n1/fault_inject/probability
+echo 1 > /sys/kernel/debug/nvme0n1/fault_inject/status
+echo 0 > /sys/kernel/debug/nvme0n1/fault_inject/dont_retry
+
+cp a.file /mnt
+
+Expected Result:
+
+command success without error
+
+Message from dmesg:
+
+FAULT_INJECTION: forcing a failure.
+name fault_inject, interval 1, probability 100, space 0, times 1
+CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.15.0-rc8+ #4
+Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
+Call Trace:
+  <IRQ>
+  dump_stack+0x5c/0x7d
+  should_fail+0x148/0x170
+  nvme_should_fail+0x30/0x60 [nvme_core]
+  nvme_loop_queue_response+0x84/0x110 [nvme_loop]
+  nvmet_req_complete+0x11/0x40 [nvmet]
+  nvmet_bio_done+0x28/0x40 [nvmet]
+  blk_update_request+0xb0/0x310
+  blk_mq_end_request+0x18/0x60
+  flush_smp_call_function_queue+0x3d/0xf0
+  smp_call_function_single_interrupt+0x2c/0xc0
+  call_function_single_interrupt+0xa2/0xb0
+  </IRQ>
+RIP: 0010:native_safe_halt+0x2/0x10
+RSP: 0018:ffffc9000068bec0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff04
+RAX: ffffffff817a10c0 RBX: ffff88011a3c9680 RCX: 0000000000000000
+RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
+RBP: 0000000000000001 R08: 000000008e38c131 R09: 0000000000000000
+R10: 0000000000000000 R11: 0000000000000000 R12: ffff88011a3c9680
+R13: ffff88011a3c9680 R14: 0000000000000000 R15: 0000000000000000
+  ? __sched_text_end+0x4/0x4
+  default_idle+0x18/0xf0
+  do_idle+0x150/0x1d0
+  cpu_startup_entry+0x6f/0x80
+  start_secondary+0x187/0x1e0
+  secondary_startup_64+0xa5/0xb0