Re: [PATCH #upstream] libata: retry failed FLUSH if device didn't fail it

[Jeff Garzik <jeff@garzik.org>]

On 11/19/2009 01:36 AM, Tejun Heo wrote:
> If ATA device failed FLUSH, it means that the device failed to write
> out some amount of data and the error needs to be reported to upper
> layers. As retries can't recover the lost data, FLUSH failures need to
> be reported immediately in general.
>
> However, if FLUSH fails due to transmission errors, the FLUSH needs to
> be retried; otherwise, filesystems may switch to RO mode and/or raid
> array may drop a drive for a random transmission glitch.
>
> This condition can be rather easily reproduced on certain ahci
> controllers which go through a PHY event after powersave mode switch +
> ext4 combination.  Powersave mode switch is often closely followed by
> flush from the filesystem failing the FLUSH with ATA bus error which
> makes the filesystem code believe that data is lost and drop to RO
> mode.  This was reported in the following bugzilla bug.
>
>    http://bugzilla.kernel.org/show_bug.cgi?id=14543
>
> This patch makes libata EH retry FLUSH if it wasn't failed by the
> device.
>
> Signed-off-by: Tejun Heo<tj@kernel.org>
> Reported-by: Andrey Vihrov<andrey.vihrov@gmail.com>
> ---
>   drivers/ata/libata-eh.c |   94 ++++++++++++++++++++++++++++++++++++++++++++++++
>   include/linux/libata.h  |    2 -
>   2 files changed, 95 insertions(+), 1 deletion(-)

applied