Re: [PATCH] UBI: fix refill_wl_user_pool()

[Richard Weinberger <richard@nod.at>]

David,

Am 04.09.2013 18:03, schrieb David Mosberger-Tang:
> Thanks for the info.  We are not using FASTMAP, so it doesn't explain
> what we're seeing.

Maybe you are suffering from the issue fixed by:
http://git.infradead.org/linux-ubi.git/commit/5ef4414f4bc26a19cfd5cd11aee9697a863e4d51

This patch will hopefully make it into 3.12-rc1 and then back into -stable as soon as possible.

Thanks,
//richard

> Best regards,
> 
>   --david
> 
> On Wed, Sep 4, 2013 at 10:01 AM, Richard Weinberger <richard@nod.at> wrote:
>> David,
>>
>> Am 04.09.2013 17:50, schrieb David Mosberger-Tang:
>>> Richard,
>>>
>>> Is there more background on the bug this patch fixes?
>>> We are working on root-causing an issue where a UBIFS write fails with
>>> ENOSPC, even though there is no plausible reason that the filesystem
>>> should be out of space.  The ENOSPC errors persist across multiple
>>> reboots, only to disappear magically later on.  We haven't found a
>>> reliable way to reproduce this so far, so we're still tapping a bit in
>>> the dark.
>>
>> The said patch fixes an issue if your Kernel was build with experimental Fastmap support.
>> If you have CONFIG_MTD_UBI_FASTMAP=n you are not affected.
>>
>> Fastmap uses two pools of available PEBs. Every time a pool is filled with used PEBs
>> it writes out a new fastmap to the flash.
>> The bug in refill_wl_user_pool() was that the function did not try hard enough to get a free PEB
>> and failed too early with -ENOSPC.
>>
>> Thanks,
>> //richard
>>
>>>   --david
>>>
>>> On Wed, Sep 4, 2013 at 2:20 AM, Richard Weinberger <richard@nod.at> wrote:
>>>> Am 26.08.2013 12:08, schrieb Richard Weinberger:
>>>>> If no free PEBs are available refill_wl_user_pool() must not
>>>>> return with -ENOSPC immediately.
>>>>> It has to block till produce_free_peb() produced a free PEB.
>>>>>
>>>>> Reported-and-Tested-by: Richard Genoud <richard.genoud@gmail.com>
>>>>> Signed-off-by: Richard Weinberger <richard@nod.at>
>>>>> ---
>>>>>  drivers/mtd/ubi/wl.c | 4 ----
>>>>>  1 file changed, 4 deletions(-)
>>>>>
>>>>> diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
>>>>> index c95bfb1..02317c1 100644
>>>>> --- a/drivers/mtd/ubi/wl.c
>>>>> +++ b/drivers/mtd/ubi/wl.c
>>>>> @@ -599,10 +599,6 @@ static void refill_wl_user_pool(struct ubi_device *ubi)
>>>>>       return_unused_pool_pebs(ubi, pool);
>>>>>
>>>>>       for (pool->size = 0; pool->size < pool->max_size; pool->size++) {
>>>>> -             if (!ubi->free.rb_node ||
>>>>> -                (ubi->free_count - ubi->beb_rsvd_pebs < 1))
>>>>> -                     break;
>>>>> -
>>>>>               pool->pebs[pool->size] = __wl_get_peb(ubi);
>>>>>               if (pool->pebs[pool->size] < 0)
>>>>>                       break;
>>>>>
>>>>
>>>> Artem, please don't forget do apply this patch.
>>>>
>>>> Thanks,
>>>> //richard
>>>>
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>>