Kernel with MTD_UBI_FASTMAP=y, fm_autoconvert=0 fails to attach and resize UBI image

[Philipp Zabel]

Hi Richard,

Am Montag, den 03.12.2012, 21:01 +0100 schrieb Richard Weinberger:
> Philipp,
> 
> Am Mon, 03 Dec 2012 15:06:54 +0100
> schrieb Philipp Zabel <p.zabel at pengutronix.de>:
> 
> > Hi,
> > 
> > on v3.7-rc7 with CONFIG_MTD_UBI_FASTMAP=y, I see the following error
> > when trying to attach an UBI image without fastmap information that
> > has to be resized because it is smaller than the mtd partition size:
> > 
> >     $ cat /sys/module/ubi/parameters/fm_autoconvert
> >     N
> > 
> >     $ ubiattach -p /dev/mtd3
> >     ubiattach: error!: cannot attach "/dev/mtd3"
> >                error 28 (No space left on device)
> > 
> > If I either disable MTD_UBI_FASTMAP in the kernel config or enable the
> > fm_autoconvert module parameter, attaching works just fine.
> > 
> > Without fm_autoconvert, ubi_resize_volume fails with -ENOSPC, caused
> > by ubi_wl_get_peb due to pool->size == 0.
> > It gets to this point on an otherwise empty flash because ubi_scan_all
> > puts all PEBs into the erase list. erase_work doesn't seem to be
> > scheduled before ubi_wl_init returns with ubi->free.rb_node == NULL
> > and ubi->free_count == 0. Because of this, refill_wl_user_pool breaks
> > out of its loop immediately and never increases the pool->size
> > counter.
> > 
> > If I force synchronous erase in ubi_wl_init, the ubiattach succeeds
> > the next time I try it as now all PEBs go in the free list:
> > 
> > @@ -1899,7 +1907,7 @@ int ubi_wl_init(struct ubi_device *ubi, struct
> > ubi_attach_info *ai) e->ec = aeb->ec;
> >                 ubi_assert(!ubi_is_fm_block(ubi, e->pnum));
> >                 ubi->lookuptbl[e->pnum] = e;
> > -               if (schedule_erase(ubi, e, aeb->vol_id, aeb->lnum,
> > 0)) {
> > +               if (do_sync_erase(ubi, e, aeb->vol_id, aeb->lnum, 0))
> > { kmem_cache_free(ubi_wl_entry_slab, e);
> >                         goto out_free;
> >                 }
> > 
> 
> Thanks a lot for identifying this issue!
> But I'm not sure whether do_sync_erase() is the perfect solution
> for the issue. Tomorrow I'll try to reproduce it.

Thank you, I'm sure it is not. Enabling fm_autoconvert works for me, so
I just wanted to put all information I've got out there before wasting
too much time trying to wrap my head around the issue myself.

regards
Philipp