Re: [PATCH] mtd: fix calculating partition end address

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Rafał,

Rafał Miłecki <rafal@milecki.pl> wrote on Sat, 02 May 2020 21:36:24
+0200:

> On 2020-05-02 20:04, Miquel Raynal wrote:
> > Miquel Raynal <miquel.raynal@bootlin.com> wrote on Mon, 9 Mar 2020
> > 16:22:23 +0100:
> >   
> >> Hi Rafał,  
> >> >> Rafał Miłecki <rafal@milecki.pl> wrote on Mon, 9 Mar 2020 16:08:12  
> >> +0100:  
> >> >> > On 09.03.2020 15:22, Miquel Raynal wrote:  
> >> > > Rafał Miłecki <rafal@milecki.pl> wrote on Mon, 09 Mar 2020 15:19:10
> >> > > +0100:
> >> > >  
> >> > >> On 2020-03-09 15:04, Miquel Raynal wrote:  
> >> > >>> Rafał Miłecki <zajec5@gmail.com> wrote on Mon,  9 Mar 2020 08:44:45
> >> > >>> +0100:  
> >> > >>>    >>>> From: Rafał Miłecki <rafal@milecki.pl>  
> >> > >>>>>> This fixes check for partitions that don't start at beginning of their  
> >> > >>>> parents. Missing partition's offset in formula could result in forcing
> >> > >>>> read-only incorrectly.  
> >> > >>>>>> Fixes: 6750f61a13a0 ("mtd: improve calculating partition boundaries >> when checking for alignment")  
> >> > >>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
> >> > >>>> ---
> >> > >>>>   drivers/mtd/mtdpart.c | 2 +-
> >> > >>>>   1 file changed, 1 insertion(+), 1 deletion(-)  
> >> > >>>>>> diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c  
> >> > >>>> index 7328c066c5ba..c683b432cc5e 100644
> >> > >>>> --- a/drivers/mtd/mtdpart.c
> >> > >>>> +++ b/drivers/mtd/mtdpart.c
> >> > >>>> @@ -524,7 +524,7 @@ static struct mtd_part *allocate_partition(struct >> mtd_info *parent,
> >> > >>>>   			part->name);
> >> > >>>>   	}  
> >> > >>>>>> -	tmp = part_absolute_offset(parent) + slave->mtd.size;  
> >> > >>>> +	tmp = part_absolute_offset(parent) + slave->offset + >> slave->mtd.size;  
> >> > >>>
> >> > >>> I think you are doing the change at the wrong place, if you want to
> >> > >>> check where the partition *starts* you should do it a few lines above.
> >> > >>> But I think the check should be here as well, probably.  
> >> > >>
> >> > >> The check where the partition *starts* is OK and I don't mean to change
> >> > >> it. The bug is about calculating absolute *end* address of partition.  
> >> > >
> >> > > Can you detail a little bit then? Because I don't see the issue anymore
> >> > > even though I am convinced something is wrong here :)  
> >> >
> >> > Please consider following partitions layout:
> >> > * bcm47xxsflash
> >> > ├─ boot		0x000000000000-0x000000040000
> >> > └┬ firmware	0x000000040000-0x000001000000
> >> >   ├─ linux	0x00000000001c-0x00000018f800
> >> >   └┬ container	0x00000018f800-0x000000fc0000
> >> >    ├─ foo	0x000000000000-0x000000630800
> >> >    └─ bar	0x000000630800-0x000000e30800 (size: 0x800000)
> >> >
> >> >
> >> > Existing (correct) *start* calculation:
> >> > bar start: 0 + 0x040000 + 0x18f800 + 0x630800 = 0x800000
> >> >
> >> > Existing (wrong) end calculation:
> >> > bar end: 0 + 0x040000 + 0x18f800 + 0x800000 = 0x9cf800
> >> >
> >> > Fixed (correct) end calculation:
> >> > bar end: 0 + 0x040000 + 0x18f800 + 0x630800 + 0x800000 = 0x1000000  
> >> >> Ok I get it! I think mentioning "partitions that don't start at  
> >> beginning of their parents", despite being true, was misleading to me
> >> as I understood "leaving extra space with the start of their parent".  
> >> >> I suppose you also have the issue with "container" too?
> >> >> Anyway, I think the fix is fine. A better formulation for the commit  
> >> log would be welcome :) (maybe adding this example is a good idea!)  
> > 
> > I don't remember having applied this fix yet, would you mind resending
> > this patch with an enhanced commit log (your example was a good one I
> > think).  
> 
> It's not needed anymore. Please check discussion we got:
> 
> -------- Original Message --------
> Subject: Re: [PATCH] mtd: fix calculating partition end address
> Date: 2020-03-24 23:11
> 
> > > I would like to apply your fix this week, do you think you can rebase
> > > and resend soon?  
> > 
> > It's not needed anymore as you fixed this bug in your commit reworking
> > partitions.  
> 
> Great!

Yeah sorry about that, I got confused while listing remaining patches :)

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