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linux/kernel
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Waiman Long 5acb3cc2c2 blktrace: Fix potential deadlock between delete & sysfs ops 
The lockdep code had reported the following unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(s_active#228);
                               lock(&bdev->bd_mutex/1);
                               lock(s_active#228);
  lock(&bdev->bd_mutex);

 *** DEADLOCK ***

The deadlock may happen when one task (CPU1) is trying to delete a
partition in a block device and another task (CPU0) is accessing
tracing sysfs file (e.g. /sys/block/dm-1/trace/act_mask) in that
partition.

The s_active isn't an actual lock. It is a reference count (kn->count)
on the sysfs (kernfs) file. Removal of a sysfs file, however, require
a wait until all the references are gone. The reference count is
treated like a rwsem using lockdep instrumentation code.

The fact that a thread is in the sysfs callback method or in the
ioctl call means there is a reference to the opended sysfs or device
file. That should prevent the underlying block structure from being
removed.

Instead of using bd_mutex in the block_device structure, a new
blk_trace_mutex is now added to the request_queue structure to protect
access to the blk_trace structure.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Fix typo in patch subject line, and prune a comment detailing how
the code used to work.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-09-25 08:56:05 -06:00
..
bpf bpf/verifier: reject BPF_ALU64|BPF_END 2017-09-15 15:01:32 -07:00
cgroup Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-09-12 11:30:56 -07:00
configs ANDROID: binder: add hwbinder,vndbinder to BINDER_DEVICES. 2017-08-22 18:43:23 -07:00
debug
events Merge branch 'for-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2017-09-06 22:25:25 -07:00
gcov gcov: support GCC 7.1 2017-05-12 15:57:15 -07:00
irq genirq: Fix cpumask check in __irq_startup_managed() 2017-09-16 20:20:56 +02:00
livepatch livepatch: Fix stacking of patches with respect to RCU 2017-06-20 10:42:19 +02:00
locking mm: treewide: remove GFP_TEMPORARY allocation flag 2017-09-13 18:53:16 -07:00
power Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-09-12 11:30:56 -07:00
printk Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk 2017-09-07 21:00:52 -07:00
rcu treewide: make "nr_cpu_ids" unsigned 2017-09-08 18:26:48 -07:00
sched sched/wait: Introduce wakeup boomark in wake_up_page_bit 2017-09-14 09:56:18 -07:00
time drivers/pps: aesthetic tweaks to PPS-related content 2017-09-08 18:26:51 -07:00
trace blktrace: Fix potential deadlock between delete & sysfs ops 2017-09-25 08:56:05 -06:00
.gitignore
acct.c fs: make the buf argument to __kernel_write a void pointer 2017-09-04 19:05:15 -04:00
async.c async: Adjust system_state checks 2017-05-23 10:01:37 +02:00
audit_fsnotify.c Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2017-05-03 11:05:15 -07:00
audit_tree.c Merge branch 'fsnotify' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs 2017-05-03 11:05:15 -07:00
audit_watch.c audit/stable-4.13 PR 20170816 2017-08-16 16:48:34 -07:00
audit.c audit: update the function comments 2017-09-05 09:46:59 -04:00
audit.h ipc: mqueue: Replace timespec with timespec64 2017-09-03 20:21:24 -04:00
auditfilter.c audit: kernel generated netlink traffic should have a portid of 0 2017-05-02 10:16:05 -04:00
auditsc.c Merge branch 'work.ipc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-09-14 17:37:26 -07:00
backtracetest.c
bounds.c
capability.c
compat.c semtimedop(): move compat to native 2017-07-15 20:46:47 -04:00
configs.c
context_tracking.c
cpu_pm.c PM / CPU: replace raw_notifier with atomic_notifier 2017-07-31 13:09:49 +02:00
cpu.c Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-09-04 13:53:53 -07:00
crash_core.c kdump: protect vmcoreinfo data under the crash memory 2017-07-12 16:26:00 -07:00
crash_dump.c
cred.c doc: ReSTify credentials.txt 2017-05-18 10:30:19 -06:00
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2017-09-11 18:34:47 -07:00
extable.c lib/extable.c: use bsearch() library function in search_extable() 2017-07-10 16:32:35 -07:00
fork.c selinux/stable-4.14 PR 20170831 2017-09-12 13:21:00 -07:00
freezer.c
futex_compat.c
futex.c futex: Remove duplicated code and fix undefined behaviour 2017-08-25 22:49:59 +02:00
groups.c kernel/groups.c: use sort library function 2017-07-10 16:32:34 -07:00
hung_task.c kernel/hung_task.c: defer showing held locks 2017-05-08 17:15:10 -07:00
irq_work.c
jump_label.c jump_label: Provide hotplug context variants 2017-08-10 12:28:59 +02:00
kallsyms.c kernel/kallsyms.c: replace all_var with IS_ENABLED(CONFIG_KALLSYMS_ALL) 2017-07-10 16:32:34 -07:00
kcmp.c kcmp: add KCMP_EPOLL_TFD mode to compare epoll target files 2017-07-12 16:26:01 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kcov: support compat processes 2017-09-08 18:26:51 -07:00
kexec_core.c x86/mm, kexec: Allow kexec to be used with SME 2017-07-18 11:38:04 +02:00
kexec_file.c kexec_file: adjust declaration of kexec_purgatory 2017-07-12 16:26:02 -07:00
kexec_internal.h kexec_file: adjust declaration of kexec_purgatory 2017-07-12 16:26:02 -07:00
kexec.c kdump: protect vmcoreinfo data under the crash memory 2017-07-12 16:26:00 -07:00
kmod.c kmod: move #ifdef CONFIG_MODULES wrapper to Makefile 2017-09-08 18:26:51 -07:00
kprobes.c kprobes: Ensure that jprobe probepoints are at function entry 2017-07-08 11:05:35 +02:00
ksysfs.c kexec: move vmcoreinfo out of the kernel's .bss section 2017-07-12 16:25:59 -07:00
kthread.c kernel/kthread.c: kthread_worker: don't hog the cpu 2017-08-31 16:33:15 -07:00
latencytop.c
Makefile kmod: move #ifdef CONFIG_MODULES wrapper to Makefile 2017-09-08 18:26:51 -07:00
memremap.c mm/device-public-memory: device memory cache coherent with CPU 2017-09-08 18:26:46 -07:00
module_signing.c
module-internal.h
module.c module: fix ddebug_remove_module() 2017-07-25 15:08:32 +02:00
notifier.c
nsproxy.c
padata.c padata: Avoid nested calls to cpus_read_lock() in pcrypt_init_padata() 2017-05-26 10:10:37 +02:00
panic.c locking/refcounts, x86/asm: Implement fast refcount overflow protection 2017-08-17 10:40:26 +02:00
params.c boot/param: Move next_arg() function to lib/cmdline.c for later reuse 2017-04-18 10:37:13 +02:00
pid_namespace.c userns,pidns: Verify the userns for new pid namespaces 2017-07-20 07:43:58 -05:00
pid.c pids: make task_tgid_nr_ns() safe 2017-08-21 12:47:31 -07:00
profile.c
ptrace.c signal: Remove kernel interal si_code magic 2017-07-24 14:30:28 -05:00
range.c
reboot.c
relay.c Merge branch 'work.splice' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-05-02 11:38:06 -07:00
resource.c
seccomp.c seccomp: Switch from atomic_t to recount_t 2017-06-26 09:24:00 -07:00
signal.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2017-09-11 18:34:47 -07:00
smp.c treewide: make "nr_cpu_ids" unsigned 2017-09-08 18:26:48 -07:00
smpboot.c
smpboot.h
softirq.c
stacktrace.c
stop_machine.c stop_machine: Provide stop_machine_cpuslocked() 2017-05-26 10:10:36 +02:00
sys_ni.c
sys.c prctl: Allow local CAP_SYS_ADMIN changing exe_file 2017-07-20 07:46:07 -05:00
sysctl_binary.c fs: fix kernel_write prototype 2017-09-04 19:05:15 -04:00
sysctl.c kernel/watchdog: split up config options 2017-07-12 16:26:02 -07:00
task_work.c task_work: Replace spin_unlock_wait() with lock/unlock pair 2017-07-25 10:08:58 -07:00
taskstats.c taskstats: add e/u/stime for TGID command 2017-05-08 17:15:12 -07:00
test_kprobes.c
torture.c torture: Fix typo suppressing CPU-hotplug statistics 2017-07-25 13:04:45 -07:00
tracepoint.c
tsacct.c
ucount.c
uid16.c
umh.c kmod: split out umh code into its own file 2017-09-08 18:26:50 -07:00
up.c smp: Avoid using two cache lines for struct call_single_data 2017-08-29 15:14:38 +02:00
user_namespace.c userns,pidns: Verify the userns for new pid namespaces 2017-07-20 07:43:58 -05:00
user-return-notifier.c
user.c
utsname_sysctl.c
utsname.c
watchdog_hld.c kernel/watchdog: Prevent false positives with turbo modes 2017-08-18 12:35:02 +02:00
watchdog.c kernel/watchdog: Prevent false positives with turbo modes 2017-08-18 12:35:02 +02:00
workqueue_internal.h
workqueue.c Merge branch 'for-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2017-09-06 21:59:31 -07:00