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Commit 14a73f54 authored by Carl Henrik Lunde's avatar Carl Henrik Lunde Committed by Linus Torvalds
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block: disable IRQs until data is written to relay channel 



As we may run relay_reserve from interrupt context we must always disable
IRQs.  This is because a call to relay_reserve may expose previously written
data to use space.

Updated new message code and an old but related comment.

Signed-off-by: default avatarCarl Henrik Lunde <chlunde@ping.uio.no>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 95dcf835

block/blktrace.c

+4 −6
Original line number Diff line number Diff line
@@ -79,16 +79,17 @@ void __trace_note_message(struct blk_trace *bt, const char *fmt, ...) 
{

	int n;

	va_list args;

	unsigned long flags;

	char *buf;



	preempt_disable();

	local_irq_save(flags);

	buf = per_cpu_ptr(bt->msg_data, smp_processor_id());

	va_start(args, fmt);

	n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);

	va_end(args);



	trace_note(bt, 0, BLK_TN_MESSAGE, buf, n);

	preempt_enable();

	local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(__trace_note_message);
@@ -158,10 +159,7 @@ void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes, 
	/*

	 * A word about the locking here - we disable interrupts to reserve

	 * some space in the relay per-cpu buffer, to prevent an irq

	 * from coming in and stepping on our toes. Once reserved, it's

	 * enough to get preemption disabled to prevent read of this data

	 * before we are through filling it. get_cpu()/put_cpu() does this

	 * for us

	 * from coming in and stepping on our toes.

	 */

	local_irq_save(flags);