From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 16 Aug 2018 10:38:02 -0400 From: Steven Rostedt To: Masami Hiramatsu Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Jens Axboe , linux-block@vger.kernel.org Subject: Re: [PATCH 2/2] tracing/blktrace: Fix to allow setting same value Message-ID: <20180816103802.08678002@gandalf.local.home> In-Reply-To: <153441307534.6024.2684721209411781531.stgit@devbox> References: <153441301698.6024.1680500212551396320.stgit@devbox> <153441307534.6024.2684721209411781531.stgit@devbox> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-ID: On Thu, 16 Aug 2018 18:51:15 +0900 Masami Hiramatsu wrote: > 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 > > Signed-off-by: Masami Hiramatsu > Cc: Jens Axboe > Cc: linux-block@vger.kernel.org > --- > kernel/trace/blktrace.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c > index 987d9a9ae283..e67db1e8a000 100644 > --- a/kernel/trace/blktrace.c > +++ b/kernel/trace/blktrace.c > @@ -1602,11 +1602,11 @@ static int blk_trace_remove_queue(struct request_queue *q) > struct blk_trace *bt; > > bt = xchg(&q->blk_trace, NULL); > - if (bt == NULL) > - return -EINVAL; > + if (bt != NULL) { > + put_probe_ref(); > + blk_trace_free(bt); > + } > > - put_probe_ref(); > - blk_trace_free(bt); > return 0; > } > > @@ -1619,6 +1619,9 @@ static int blk_trace_setup_queue(struct request_queue *q, > struct blk_trace *bt = NULL; > int ret = -ENOMEM; > > + if (q->blk_trace) > + return 0; > + > bt = kzalloc(sizeof(*bt), GFP_KERNEL); > if (!bt) > return -ENOMEM; Hmm, why not just do this? Does this fix it too? diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index 987d9a9ae283..10b2b9c5fd25 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -1841,6 +1841,8 @@ 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) + goto out_unlock_bdev; if (value) ret = blk_trace_setup_queue(q, bdev); else -- Steve