On Tue, Apr 17, 2012 at 8:07 AM, Shaohua Li <shli@xxxxxxxxxx> wrote:
> Hi Dan,
>
> On 4/17/12 10:46 PM, Dan Williams wrote:
>>
>> On Tue, Apr 17, 2012 at 1:35 AM, Shaohua Li<shli@xxxxxxxxxx> wrote:
>>>
>>> Discard for raid4/5/6 has limitation. If discard request size is small,
>>> we do
>>> discard for one disk, but we need calculate parity and write parity disk.
>>> To
>>> correctly calculate parity, zero_after_discard must be guaranteed.
>>
>>
>> I'm wondering if we could use the new bad blocks facility to mark
>> discarded ranges so we don't necessarily need determinate data after
>> discard.
>
>
> It would be great the limitation can be avoided and the code can be
> simplified. I didn't follow linux-raid maillist, can you point me the url
> of the new bad blocks facility please?
It came in at 3.1 starting with:
commit 2230dfe4ccc3add340dc6d437965b2de1d269fde
Author: NeilBrown <neilb@xxxxxxx>
Date: Thu Jul 28 11:31:46 2011 +1000
md: beginnings of bad block management.
This the first step in allowing md to track bad-blocks per-device so
that we can fail individual blocks rather than the whole device.
This patch just adds a data structure for recording bad blocks, with
routines to add, remove, search the list.
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Reviewed-by: Namhyung Kim <namhyung@xxxxxxxxx>
Here is a link to the patch set:
http://marc.info/?l=linux-raid&m=131121721902900&w=2
--
Dan
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