Re: [PATCH] UBI: fix refill_wl_user_pool()

[Richard Weinberger <richard@nod.at>]

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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