Messages in this thread Patch in this message | | | Date | Thu, 16 Aug 2018 16:08:37 -0400 | From | Steven Rostedt <> | Subject | [PATCH] tracing/blktrace: Fix to allow setting same value |
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[ Jens, you want to take this one, or do you want me to? ]
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Masami Hiramatsu reported:
Current trace-enable attribute in sysfs returns an error if user writes the same setting value as current one, e.g.
# cat /sys/block/sda/trace/enable 0 # echo 0 > /sys/block/sda/trace/enable bash: echo: write error: Invalid argument # echo 1 > /sys/block/sda/trace/enable # echo 1 > /sys/block/sda/trace/enable bash: echo: write error: Device or resource busy
But this is not a preferred behavior, it should ignore if new setting is same as current one. This fixes the problem as below.
# cat /sys/block/sda/trace/enable 0 # echo 0 > /sys/block/sda/trace/enable # echo 1 > /sys/block/sda/trace/enable # echo 1 > /sys/block/sda/trace/enable
Link: http://lkml.kernel.org/r/20180816103802.08678002@gandalf.local.home
Cc: Ingo Molnar <mingo@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: linux-block@vger.kernel.org Cc: stable@vger.kernel.org Fixes: cd649b8bb830d ("blktrace: remove sysfs_blk_trace_enable_show/store()") Reported-by: Masami Hiramatsu <mhiramat@kernel.org> Tested-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> --- kernel/trace/blktrace.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index b82e546083e1..614b5f0decd6 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -1829,6 +1829,10 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, mutex_lock(&q->blk_trace_mutex); if (attr == &dev_attr_enable) { + if (!!value == !!q->blk_trace) { + ret = 0; + goto out_unlock_bdev; + } if (value) ret = blk_trace_setup_queue(q, bdev); else -- 2.13.6
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