linux-kernel - Re: [PATCH 2/3] libata: add support for blk-iopoll

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Message-ID: <20090810111523.035e0d20@bike.lwn.net>
Date:	Mon, 10 Aug 2009 11:15:23 -0600
From:	Jonathan Corbet <corbet@....net>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	Eric.Moore@....com, jeff@...zik.org,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [PATCH 2/3] libata: add support for blk-iopoll

Hey, Jens,

I'm a little slow in looking at this, hopefully it's not completely
noise...

> @@ -2157,7 +2194,12 @@ static irqreturn_t ahci_interrupt(int irq, void *dev_instance)
>  
>  		ap = host->ports[i];
>  		if (ap) {
> -			ahci_port_intr(ap);
> +			if (!blk_iopoll_enabled)
> +				ahci_port_intr(ap);
> +			else if (blk_iopoll_sched_prep(&ap->iopoll)) {
> +				ap_irq_disable(ap);
> +				blk_iopoll_sched(&ap->iopoll);
> +			}
>  			VPRINTK("port %u\n", i);
>  		} else {
>  			VPRINTK("port %u (no irq)\n", i);

It seems to me that, if blk_iopoll_sched_prep() fails, the interrupt
will be dropped on the floor; would you not need an explicit
ahci_port_intr() call in that case too?  Unless I've misunderstood as
usual...

Documenting the "zero means failure" nature of blk_iopoll_sched_prep()
might also be a good idea; I predict confusion otherwise.

jon
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