[PATCH] UBI: fix refill_wl_user_pool()

[David Mosberger-Tang]

The platform we're seeing this on is running an old kernel: 2.6.27.10.
We don't know yet whether it happens on newer kernels (we are trying
to reproduce the issue on both older and newer kernels, but that may
take a month; so far, we have only seen the issue on systems in the
field).

  --david


On Thu, Sep 5, 2013 at 12:09 AM, Richard Weinberger <richard at nod.at> wrote:
> 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 at 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 at 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 at gmail.com>
>>>>>> Signed-off-by: Richard Weinberger <richard at 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
>>>>>
>>>>> ______________________________________________________
>>>>> Linux MTD discussion mailing list
>>>>> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>>>
>