3.16.62-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: "Steven Rostedt (VMware)" <[email protected]> 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/[email protected] Cc: Ingo Molnar <[email protected]> Cc: Jens Axboe <[email protected]> Cc: [email protected] Fixes: cd649b8bb830d ("blktrace: remove sysfs_blk_trace_enable_show/store()") Reported-by: Masami Hiramatsu <[email protected]> Tested-by: Masami Hiramatsu <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]> Signed-off-by: Jens Axboe <[email protected]> Signed-off-by: Ben Hutchings <[email protected]> --- kernel/trace/blktrace.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -1778,6 +1778,10 @@ static ssize_t sysfs_blk_trace_attr_stor 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
