Re: [PATCH] ubi: Fix filesystem corruption on detach when fastmap enabled

[Richard Weinberger <richard@sigma-star.at>]

Martin,

Am Dienstag, 16. Januar 2018, 15:13:04 CET schrieb Martin Townsend:
> > Martin, can you please explain what corruption you see?
> > From reading the code I'd assume that you miss volumes but a full scan
> > would recover everything.
> 
> I didn't do much analysis of the corruption I'm afraid.  When I tried
> to reattach the the c->empty flag was set to true and indeed all the
> EBA tables were reporting an empty filesystem even after a reboot.

Sounds like what I'd expect.

> Not sure if this was recoverable, how do you trigger a full scan?

Booting a kernel without Fastmap support. B-)

> > For Linux I suggest this fix:
> > 
> > From 48287459cf8717cffac5aed423937cd7ba4360ab Mon Sep 17 00:00:00 2001
> > From: Richard Weinberger <richard@nod.at>
> > Date: Tue, 16 Jan 2018 14:12:46 +0100
> > Subject: [PATCH] ubi: fastmap: Don't flush fastmap work on detach
> > 
> > At this point UBI volumes have already been free()'ed and fastmap can no
> > longer access these data structures.
> > 
> > Fixes: 74cdaf24004a ("UBI: Fastmap: Fix memory leaks while closing the WL
> > sub- system")
> > Signed-off-by: Richard Weinberger <richard@nod.at>
> > Cc: stable@vger.kernel.org
> > ---
> > 
> >  drivers/mtd/ubi/fastmap-wl.c | 1 -
> >  1 file changed, 1 deletion(-)
> > 
> > diff --git a/drivers/mtd/ubi/fastmap-wl.c b/drivers/mtd/ubi/fastmap-wl.c
> > index 4f0bd6b4422a..69dd21679a30 100644
> > --- a/drivers/mtd/ubi/fastmap-wl.c
> > +++ b/drivers/mtd/ubi/fastmap-wl.c
> > @@ -362,7 +362,6 @@ static void ubi_fastmap_close(struct ubi_device *ubi)
> > 
> >  {
> >  
> >         int i;
> > 
> > -       flush_work(&ubi->fm_work);
> > 
> >         return_unused_pool_pebs(ubi, &ubi->fm_pool);
> >         return_unused_pool_pebs(ubi, &ubi->fm_wl_pool);
> > 
> > --
> > 2.13.6
> > 
> > In U-Boot you can do the same.
>
> Richard: This will work but just want to check that ubi_wl_close is
> supposed to never write out to the filesystem or will never do so in
> future, if so maybe a something in the comments above ubi_wl_close to
> ensure this?

Hmm, not sure if I got this question.
The filesystem sits above UBI. If we reach ubi_wl_close() all users ontop of 
UBI are gone. There is no UBIFS mounted anymore.

Thanks,
//richard

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