linux-kernel - Re: [PATCH 1/2] don't wait on disk to start on resume

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Message-ID: <CAGAzgso4cJHM+CNV0nCu6zUmq=xUstbsguynUp+hyx581LcHJg@mail.gmail.com>
Date:	Thu, 31 Jan 2013 14:00:09 -0800
From:	"dbasehore ." <dbasehore@...omium.org>
To:	Sergei Shtylyov <sshtylyov@...sta.com>
Cc:	JBottomley@...allels.com, jgarzik@...ox.com,
	linux-ide@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH 1/2] don't wait on disk to start on resume

(Resending as plain text so the message is tracked on vger)

Hi, thanks for reading through my patch.

With regards to SCSI_SENSE_BUFFERSIZE, I'm following the precedent of
scsi_execute_req found in drivers/scsi/scsi_lib.c

It seems that it is used by the scsi_normalize_sense function which I
call in sd_resume_async. I just input SCSI_SENSE_BUFFERSIZE directly
there though. I didn't know if anything would change its behavior on a
lower level if I made sense_len = SCSI_SENSE_BUFFERSIZE, so I just
went with what was already done.

I'll make sure the semantic fixes go into the final patch.

Also, I forgot to mention one possible problem earlier. I understand
that some hard drives have a command buffer that can be executed by
the hard drive in an order it determines. Does anyone know of a
potential problem if the following happens?

-resume finishes (hard drive not started yet)
-read/write sent to disk, inserted before start command

Could this happen? If so, could it cause any problems?

I've tested the possibility of a program trying to read/write from the
disk before it has started, and the read/write blocks until the disk
has actually been spun up. I don't know if there are specific hard
drives where this could be a problem though.
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