4.9-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt (VMware) rostedt@goodmis.org
commit 757d9140072054528b13bbe291583d9823cde195 upstream.
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 Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/blktrace.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -1720,6 +1720,10 @@ static ssize_t sysfs_blk_trace_attr_stor mutex_lock(&bdev->bd_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