From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Amit Sahrawat <amit.sahrawat83@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
Douglas Gilbert <dgilbert@interlog.com>,
linux-usb@vger.kernel.org, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
NamJae Jeon <linkinjeon@gmail.com>
Subject: Re: [Patch] SCSI: Retrieve Cache Mode Using SG_ATA_16 if normal routine fails
Date: Tue, 11 Oct 2011 09:05:26 -0500 [thread overview]
Message-ID: <1318341926.2992.5.camel@dabdike.int.hansenpartnership.com> (raw)
In-Reply-To: <CADDb1s2=Ykh711grVjHV542pVJwpf1K+zzTRVEY2KH3T=wB_xg@mail.gmail.com>
On Tue, 2011-10-11 at 13:56 +0530, Amit Sahrawat wrote:
> SCSI: Retrieve Cache Mode Using SG_ATA_16 if normal routine fails
>
> It has been observed that a number of USB HDD's do not respond correctly
> to SCSI mode sense command(retrieve caching pages) which results in their
> Write Cache being discarded by queue requests i.e., WCE if left set to
> '0'(disabled). So, in order to identify the devices correctly - give it
> a last try using SG_ATA_16 after failure from normal routine.
This is a non-starter, as I've said before. Apart from the layering
violation of trying to make sd ATA aware, ATA_16 is known to crash some
USB devices (the bug reports are mostly about smartctl which can be made
to use ATA_16 failing).
The correct way to implement this is to have a user visible WCE variable
that can be written to in the scsi_disk class sysfs files so the user
can alter the caching type on the fly.
James
next prev parent reply other threads:[~2011-10-11 14:05 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-11 8:26 Amit Sahrawat
2011-10-11 10:41 ` Hannes Reinecke
2011-10-11 10:55 ` Amit Sahrawat
2011-10-11 11:59 ` NamJae Jeon
2011-10-11 13:42 ` Jeff Garzik
2011-10-11 14:05 ` James Bottomley [this message]
2011-10-11 16:00 ` Amit Sahrawat
2011-10-11 14:19 ` Alan Stern
2011-10-11 16:03 ` Amit Sahrawat
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