linux-kernel - Re: [PATCH V2] block: correctly fallback for zeroout

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Date:	Fri, 10 Jun 2016 21:49:44 -0400
From:	"Martin K. Petersen" <martin.petersen@...cle.com>
To:	Shaohua Li <shli@...com>
Cc:	"Martin K. Petersen" <martin.petersen@...cle.com>,
	<linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<axboe@...com>, <sitsofe@...oo.com>, <snitzer@...hat.com>,
	<hch@...radead.org>, <Kernel-team@...com>
Subject: Re: [PATCH V2] block: correctly fallback for zeroout

>>>>> "Shaohua" == Shaohua Li <shli@...com> writes:

Shaohua,

>> What does the extra io_err buy us? Just have this function return an
>> error. And then in blkdev_issue_discard if you get -EOPNOTSUPP you
>> special case it there.

Shaohua> The __blkdev_issue_discard returns -EOPNOTSUPP if disk doesn't
Shaohua> support discard.  in that case, blkdev_issue_discard doesn't
Shaohua> return 0. blkdev_issue_discard only returns 0 if IO error is
Shaohua> -EOPNOTSUPP.

Oh, I see. The sanity checks are now in __blkdev_issue_discard() so
there is no way to distinguish between -EOPNOTSUPP and the other
-EOPNOTSUPP. *sigh*

I am OK with your patch as a stable fix but this really needs to be
fixed up properly.

-- 
Martin K. Petersen	Oracle Linux Engineering