Date: Tue, 25 Nov 2008 10:19:18 +0100
From: Jens Axboe <jens.axboe@oracle.com>
To: Keith Mannthey <kmannth@us.ibm.com>
Cc: linux-kernel@vger.kernel.org, Chandra Seetharaman <sekharan@us.ibm.com>
Subject: Re: [Patch][RFC] Supress Buffer I/O errors when SCSI REQ_QUIET flag set
Message-ID: <20081125091917.GU26308@kernel.dk>
References: <1227561983.6487.32.camel@keith-laptop>
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On Mon, Nov 24 2008, Keith Mannthey wrote:
> Allow the scsi request REQ_QUIET flag to be propagated to the buffer
> file system layer. The basic ideas is to pass the flag from the scsi
> request to the bio (block IO) and then to the buffer layer.  The buffer
> layer can then suppress needless printks. 
> 
> This patch declutters the kernel log by removed the 40-50 (per lun)
> buffer io error messages seen during a boot in my multipath setup . It
> is a good chance any real errors will be missed in the "noise" it the
> logs without this patch. 
> 
> During boot I see blocks of messages like 
> "
> __ratelimit: 211 callbacks suppressed
> Buffer I/O error on device sdm, logical block 5242879
> Buffer I/O error on device sdm, logical block 5242879
> Buffer I/O error on device sdm, logical block 5242847
> Buffer I/O error on device sdm, logical block 1
> Buffer I/O error on device sdm, logical block 5242878
> Buffer I/O error on device sdm, logical block 5242879
> Buffer I/O error on device sdm, logical block 5242879
> Buffer I/O error on device sdm, logical block 5242879
> Buffer I/O error on device sdm, logical block 5242879
> Buffer I/O error on device sdm, logical block 5242872
> "
> in my logs. 
> 
> My disk environment is multipath fiber channel using the SCSI_DH_RDAC
> code and multipathd.  This topology includes an "active" and "ghost"
> path for each lun. IO's to the "ghost" path will never complete and the
> SCSI layer, via the scsi device handler rdac code, quick returns the IOs
> to theses paths and sets the REQ_QUIET scsi flag to suppress the scsi
> layer messages. 
> 
>  I am wanting to extend the QUIET behavior to include the buffer file
> system layer to deal with these errors as well. I have been running this
> patch for a while now on several boxes without issue.  A few runs of
> bonnie++ show no noticeable difference in performance in my setup. 
> 
> Thanks for John Stultz for the quiet_error finalization. 

Looks good to me. I'll merge it up for 2.6.29.

-- 
Jens Axboe

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