linux-kernel - Re: scsi-mq V2

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Date:	Fri, 11 Jul 2014 10:55:24 -0400
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	"Elliott, Robert (Server Storage)" <Elliott@...com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Jeff Moyer <jmoyer@...hat.com>, Jens Axboe <axboe@...nel.dk>,
	"dgilbert@...erlog.com" <dgilbert@...erlog.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Bart Van Assche <bvanassche@...ionio.com>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: scsi-mq V2

On Fri, Jul 11, 2014 at 02:33:12PM +0000, Elliott, Robert (Server Storage) wrote:
> That ran 9 total hours with no problem.
> 
> Rather than revert in the bisect trees, I added just this single additional
> patch to the no-rebase tree, and the problem appeared:

Can you try the below totally untested patch instead?  It looks like
put_reqs_available() is not irq-safe.

		-ben
-- 
"Thought is the essence of where you are now."


diff --git a/fs/aio.c b/fs/aio.c
index 955947e..4b97180 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -830,16 +830,20 @@ void exit_aio(struct mm_struct *mm)
 static void put_reqs_available(struct kioctx *ctx, unsigned nr)
 {
 	struct kioctx_cpu *kcpu;
+	unsigned long flags;
 
 	preempt_disable();
 	kcpu = this_cpu_ptr(ctx->cpu);
 
+	local_irq_save(flags);
 	kcpu->reqs_available += nr;
+
 	while (kcpu->reqs_available >= ctx->req_batch * 2) {
 		kcpu->reqs_available -= ctx->req_batch;
 		atomic_add(ctx->req_batch, &ctx->reqs_available);
 	}
 
+	local_irq_restore(flags);
 	preempt_enable();
 }
 
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