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

["Rafał Miłecki" <rafal@milecki.pl>]

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!

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