blktrace: fix blk_probes_ref chaos (17ba97e3) · Commits · 戴 / test

Impact: fix mixed ioctl and ftrace-plugin blktrace use refcount bugs ioctl-based blktrace allocates bt and registers tracepoints when ioctl(BLKTRACESETUP), and do all cleanups when ioctl(BLKTRACETEARDOWN). while ftrace-based blktrace allocates/frees bt when: # echo 1/0 > /sys/block/sda/sda1/trace/enable and registers/unregisters tracepoints when: # echo blk/nop > /debugfs/tracing/current_tracer or # echo 1/0 > /debugfs/tracing/tracing_enable The separatation of allocation and registeration causes 2 problems: 1. current user-space blktrace still calls ioctl(TEARDOWN) when ioctl(SETUP) failed: # echo 1 > /sys/block/sda/sda1/trace/enable # blktrace /dev/sda BLKTRACESETUP: Device or resource busy ^C and now blk_probes_ref == -1 2. Another way to make blk_probes_ref == -1: # plugin sdb && mount sdb1 # echo 1 > /sys/block/sdb/sdb1/trace/enable # remove sdb This patch does the allocation and registeration when writing sdaX/trace/enable. Signed-off-by:

Li Zefan <lizf@cn.fujitsu.com> Acked-by:

Jens Axboe <jens.axboe@oracle.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/trace/blktrace.c

+7 −8

Original line number	Diff line number	Diff line
		@@ -478,7 +478,7 @@ int do_blk_trace_setup(struct request_queue q, char name, dev_t dev,
		goto err;
		}

		if (atomic_add_return(1, &blk_probes_ref) == 1)
		if (atomic_inc_return(&blk_probes_ref) == 1)
		blk_register_tracepoints();

		return 0;
		@@ -1091,8 +1091,6 @@ static void blk_tracer_print_header(struct seq_file *m)

		static void blk_tracer_start(struct trace_array *tr)
		{
		if (atomic_add_return(1, &blk_probes_ref) == 1)
		blk_register_tracepoints();
		trace_flags &= ~TRACE_ITER_CONTEXT_INFO;
		}

		@@ -1107,15 +1105,10 @@ static int blk_tracer_init(struct trace_array *tr)
		static void blk_tracer_stop(struct trace_array *tr)
		{
		trace_flags \|= TRACE_ITER_CONTEXT_INFO;
		if (atomic_dec_and_test(&blk_probes_ref))
		blk_unregister_tracepoints();
		}

		static void blk_tracer_reset(struct trace_array *tr)
		{
		if (!atomic_read(&blk_probes_ref))
		return;

		blk_tracer_enabled = false;
		blk_tracer_stop(tr);
		}
		@@ -1254,6 +1247,9 @@ static int blk_trace_remove_queue(struct request_queue *q)
		if (bt == NULL)
		return -EINVAL;

		if (atomic_dec_and_test(&blk_probes_ref))
		blk_unregister_tracepoints();

		kfree(bt);
		return 0;
		}
		@@ -1280,6 +1276,9 @@ static int blk_trace_setup_queue(struct request_queue *q, dev_t dev)
		return -EBUSY;
		}

		if (atomic_inc_return(&blk_probes_ref) == 1)
		blk_register_tracepoints();

		return 0;
		}

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