linux-kernel - Re: [PATCH] block: Invalidate the cache for a parent block-device if blkdev_issue

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Date:	Thu, 19 Jan 2012 15:06:42 +0000
From:	"Bryn M. Reeves" <bmr@...hat.com>
To:	Niels de Vos <ndevos@...hat.com>
CC:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: Invalidate the cache for a parent block-device
 if blkdev_issue_flush() was called for a partition

On 01/19/2012 08:50 AM, Niels de Vos wrote:
> Executing a BLKFLSBUF-ioctl on a partition flushes the caches for that
> partition but reading data through the parent device will still return
> the old cached data.
> 
> The cache for the block-device is not synced if the block-device is kept
> open (due to a mounted partition, for example). Only when all users for
> the disk have exited, the cache for the disk is made consistent again.
> 
> Calling invalidate_bdev() on the parent block-device in case
> blkdev_issue_flush() was called for a partition fixes this.
> 
> The problem can be worked around by forcing the caches to be flushed
> with either
> 	# blockdev --flushbufs ${dev_disk}
> or
> 	# echo 3 > /proc/sys/vm/drop_caches
> 
> CC: Bryn M. Reeves <bmr@...hat.com>
> Signed-off-by: Niels de Vos <ndevos@...hat.com>

Acked-by: Bryn M. Reeves <bmr@...hat.com>

Cheers,
Bryn.
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