Re: [PATCH] mtd: ubi: Fix endless loop when moving PEB

[Sascha Hauer <s.hauer@pengutronix.de>]

On Mon, Jun 27, 2016 at 10:22:38AM +0200, Teresa Remmet wrote:
> Hello Sascha,
> 
> Am Freitag, den 24.06.2016, 13:20 +0200 schrieb Sascha Hauer:
> > Hi Teresa,
> > 
> > On Wed, Jun 22, 2016 at 11:01:57AM +0200, Teresa Remmet wrote:
> > > When moving a PEB the leb_write_trylock() function is called.
> > > As the function never returns 0 UBI will end up in an endless
> > > loop.
> > > 
> > > Noticed the issue when fastmap has been enabled and data is beeing copied
> > > several times to a UBI volume. When UBI tries to move the anchor PEB,
> > > the issue comes up.
> > > 
> > > The leb_write_trylock() is now equal to the leb_write_lock().
> > > But kept it for easier maintaince in future when syncing with
> > > kernel.
> > > 
> > > Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
> > > ---
> > >  drivers/mtd/ubi/eba.c | 11 +----------
> > >  1 file changed, 1 insertion(+), 10 deletions(-)
> > > 
> > > diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
> > > index a7af247..31dbcd2 100644
> > > --- a/drivers/mtd/ubi/eba.c
> > > +++ b/drivers/mtd/ubi/eba.c
> > > @@ -257,16 +257,7 @@ static int leb_write_trylock(struct ubi_device *ubi, int vol_id, int lnum)
> > >  	le = ltree_add_entry(ubi, vol_id, lnum);
> > >  	if (IS_ERR(le))
> > >  		return PTR_ERR(le);
> > > -
> > > -	/* Contention, cancel */
> > > -	le->users -= 1;
> > > -	ubi_assert(le->users >= 0);
> > > -	if (le->users == 0) {
> > > -		rb_erase(&le->rb, &ubi->ltree);
> > > -		kfree(le);
> > > -	}
> > > -
> > > -	return 1;
> > > +	return 0;
> > >  }
> > 
> > This seems to be the missing link to make the following patch work. I
> > have tried this several times but so far never found this bug. Could you
> > give it a try? With this patch it should be now possible to ubiformat a
> > device with an image and to generate a fastmap when the device is
> > detached first.
> 
> I tested it, and it is working. Ubi now successfully writes an anchor
> PEB.

Thanks for testing. Applied both patches.

Sascha


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