Re: [PATCH] 2.4.x write barriers (updated for ext3)

Peter Osterlund
2002-03-13T22:37:55Z

Jens Axboe <axboe@suse.de> writes:

> On Mon, Mar 11 2002, Kurt Garloff wrote:
> > disks (DASDs), Write-Once and Optical Memory devices. (Funny enough, the
> > SCSI spec also lists SYNCHRONIZE_CACHE for CD-Rom devices
>
> Hey, I use SYNCHRONIZE_CACHE in the packet writing stuff for CD-ROM's
> all the time :-). Not all are read-only. In fact, Peter Osterlund
> discovered that if you have pending writes on the CD-ROM it's a really
> good idea to sync the cache prior to starting reads or they have a nasty
> tendency to time out.

Not only time out, some drives give up immediately with SK/ASC/ASCQ
05/2c/00 "command sequence error" unless you flush the cache first.
After some googling, I found a plausible explanation for that
behaviour here:

http://www.rahul.net/endl/cdaccess/t10/email/mmc/1997/m9703031.txt

--
Peter Osterlund - petero2@telia.com