Re: [PATCH] SYNCHRONIZE_CACHE on umount

[Jens Axboe <axboe@suse.de>]

On Thu, Jan 12 2006, Hifumi Hisashi wrote:
> Hi.
> When a SCSI HDD(WCE bit is set) is umounted, SYNCHRONIZE_CACHE(35h)
> command is not issued under current sd driver.
> 
> When an IDE HDD is umounted, FLUSH CACHE is issued through
> idedisk_release().
> I suppose that the sd driver also needs to flush cache through umount.
> 
> Thanks.
> 
> Signed-off-by: Hifumi Hisashi <hifumi.hisashi@lab.ntt.co.jp>
> 
> --- linux-2.6.15/drivers/scsi/sd.c      2006-01-12 16:23:44.000000000 +0900
> +++ linux-2.6.15_fix/drivers/scsi/sd.c  2006-01-12 16:43:04.000000000 +0900
> @@ -503,6 +503,8 @@
> 
>         SCSI_LOG_HLQUEUE(3, printk("sd_release: disk=%s\n", 
>         disk->disk_name));
> 
> +       if (sdkp->WCE)
> +               sd_sync_cache(sdev);
>         if (!--sdkp->openers && sdev->removable) {
>                 if (scsi_block_when_processing_errors(sdev))
>                         scsi_set_medium_removal(sdev, SCSI_REMOVAL_ALLOW);

Wrong way to place it, imo. If you are pushing out dirty data on umount,
the core should make sure to do a blkdev_issue_flush() afterwards. Then
you don't have to put it in each and every driver.

-- 
Jens Axboe