[PATCH] UBI: fastmap: Erase outdated anchor PEBs during attach

[Boris Brezillon]

On Wed, 10 Jan 2018 15:16:17 +0100
Sascha Hauer <s.hauer at pengutronix.de> wrote:

> +Cc Boris
> 
> Hi Boris and all,
> 
> I can't find this patch in any tree. Boris, will you take it?

Nope, UBI changes go through Richard's tree and then directly to Linus.

> 
> Sascha
> 
> On Tue, Dec 05, 2017 at 04:01:20PM +0100, Sascha Hauer wrote:
> > The fastmap update code might erase the current fastmap anchor PEB
> > in case it doesn't find any new free PEB. When a power cut happens
> > in this situation we must not have any outdated fastmap anchor PEB
> > on the device, because that would be used to attach during next
> > boot.
> > The easiest way to make that sure is to erase all outdated fastmap
> > anchor PEBs synchronously during attach.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
> > ---
> >  drivers/mtd/ubi/wl.c | 77 ++++++++++++++++++++++++++++++++++++++--------------
> >  1 file changed, 57 insertions(+), 20 deletions(-)
> > 
> > diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
> > index b5b8cd6f481c..668b46202507 100644
> > --- a/drivers/mtd/ubi/wl.c
> > +++ b/drivers/mtd/ubi/wl.c
> > @@ -1529,6 +1529,46 @@ static void shutdown_work(struct ubi_device *ubi)
> >  }
> >  
> >  /**
> > + * erase_aeb - erase a PEB given in UBI attach info PEB
> > + * @ubi: UBI device description object
> > + * @aeb: UBI attach info PEB
> > + * @sync: If true, erase synchronously. Otherwise schedule for erasure
> > + */
> > +static int erase_aeb(struct ubi_device *ubi, struct ubi_ainf_peb *aeb, bool sync)
> > +{
> > +	struct ubi_wl_entry *e;
> > +	int err;
> > +
> > +	e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
> > +	if (!e)
> > +		return -ENOMEM;
> > +
> > +	e->pnum = aeb->pnum;
> > +	e->ec = aeb->ec;
> > +	ubi->lookuptbl[e->pnum] = e;
> > +
> > +	if (sync) {
> > +		err = sync_erase(ubi, e, false);
> > +		if (err)
> > +			goto out_free;
> > +
> > +		wl_tree_add(e, &ubi->free);
> > +		ubi->free_count++;
> > +	} else {
> > +		err = schedule_erase(ubi, e, aeb->vol_id, aeb->lnum, 0, false);
> > +		if (err)
> > +			goto out_free;
> > +	}
> > +
> > +	return 0;
> > +
> > +out_free:
> > +	wl_entry_destroy(ubi, e);
> > +
> > +	return err;
> > +}
> > +
> > +/**
> >   * ubi_wl_init - initialize the WL sub-system using attaching information.
> >   * @ubi: UBI device description object
> >   * @ai: attaching information
> > @@ -1566,18 +1606,10 @@ int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
> >  	list_for_each_entry_safe(aeb, tmp, &ai->erase, u.list) {
> >  		cond_resched();
> >  
> > -		e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
> > -		if (!e)
> > +		err = erase_aeb(ubi, aeb, false);
> > +		if (err)
> >  			goto out_free;
> >  
> > -		e->pnum = aeb->pnum;
> > -		e->ec = aeb->ec;
> > -		ubi->lookuptbl[e->pnum] = e;
> > -		if (schedule_erase(ubi, e, aeb->vol_id, aeb->lnum, 0, false)) {
> > -			wl_entry_destroy(ubi, e);
> > -			goto out_free;
> > -		}
> > -
> >  		found_pebs++;
> >  	}
> >  
> > @@ -1635,6 +1667,8 @@ int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
> >  			ubi_assert(!ubi->lookuptbl[e->pnum]);
> >  			ubi->lookuptbl[e->pnum] = e;
> >  		} else {
> > +			bool sync = false;
> > +
> >  			/*
> >  			 * Usually old Fastmap PEBs are scheduled for erasure
> >  			 * and we don't have to care about them but if we face
> > @@ -1644,18 +1678,21 @@ int ubi_wl_init(struct ubi_device *ubi, struct ubi_attach_info *ai)
> >  			if (ubi->lookuptbl[aeb->pnum])
> >  				continue;
> >  
> > -			e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
> > -			if (!e)
> > -				goto out_free;
> > +			/*
> > +			 * The fastmap update code might not find a free PEB for
> > +			 * writing the fastmap anchor to and then reuses the
> > +			 * current fastmap anchor PEB. When this PEB gets erased
> > +			 * and a power cut happens before it is written again we
> > +			 * must make sure that the fastmap attach code doesn't
> > +			 * find any outdated fastmap anchors, hence we erase the
> > +			 * outdated fastmap anchor PEBs synchronously here.
> > +			 */
> > +			if (aeb->vol_id == UBI_FM_SB_VOLUME_ID)
> > +				sync = true;
> >  
> > -			e->pnum = aeb->pnum;
> > -			e->ec = aeb->ec;
> > -			ubi_assert(!ubi->lookuptbl[e->pnum]);
> > -			ubi->lookuptbl[e->pnum] = e;
> > -			if (schedule_erase(ubi, e, aeb->vol_id, aeb->lnum, 0, false)) {
> > -				wl_entry_destroy(ubi, e);
> > +			err = erase_aeb(ubi, aeb, sync);
> > +			if (err)
> >  				goto out_free;
> > -			}
> >  		}
> >  
> >  		found_pebs++;
> > -- 
> > 2.11.0
> > 
> >   
>