OK, this sounds good.
Since I have 15 bytes free in the oob I simply reduced n_bytes to
uint16_t in the struct definition over at yaffs_packedtags2.h.
Overall this seems to work. Does that sound reasonable?
Thanks,
Boaz.
On Thu, 2011-01-20 at 07:44 +1300, Charles Manning wrote:
> You need to find a way to pack the tags into the available space.
>
> Have a look at yaffs_packedtags2.c and .h.
>
> The basic tags structure is 4 x u32. Tags packing then rejiggers the tags
> layout for object headers to store more info in the tags space.
>
> If you forgo the extra information packing then it is easy enough to reduce
> the tags storage to
>
> seq_number keep as u32
> obj_id 24 bits is enough
> chunk_id 24 bits is enough
> n_bytes 16 bits is enough.
>
> That will reduce the tags struct to 12 bytes.
>
> -- Charles
>
>
>
> On Wednesday 19 January 2011 20:54:08 Boaz Ben-David wrote:
> > OK, I think this is indeed the problem.
> > The oob scheme declared only 4 bytes of oobfree space.
> > After some changes and testing using the mtd provided oob test I managed
> > to find some more unused bytes and now I have 15.
> > Now yaffs doesn't retire all blocks as before but actually can create
> > files on the partition. The problem is that after un-mounting and then
> > re-mounting the partition again file sizes are changing, I guess because
> > of that missing byte for the tags.
> > Is there some way I can make yaffs work with only 15 bytes free in the
> > oob area?
> >
> > On Wed, 2011-01-19 at 13:49 +1300, Charles Manning wrote:
> > > On Tuesday 18 January 2011 22:36:40 Boaz Ben-David wrote:
> > > > To sum it up, my controller (iMX353) uses HW ECC by default, and I am
> > > > using MLC nand with 4k page and 218B oob.
> > > > My question is, is it at all possible to make this work with YAFFS
> > > > using oob tags (as opposed to inband-tags that work) or am I not in the
> > > > right direction.
> > >
> > > You need at least 16 bytes of unused OOB to store tags (this could be
> > > reduced to approx 12 bytes or so with some effort). If there is less than
> > > that then you will need to use inband tags.
> > >
> > > > YAFFS gives very good performance using the inband-tags option on our
> > > > device, the only issue is that the partition I am using it on is of
> > > > 1.6GB size and when recovering from an unclean shutdown with the
> > > > partition having about 600MB on it, it takes 2:30 minutes to mount
> > > > and thats far too long.
> > > >
> > > > So again, I apologize for asking this again and again but I haven't
> > > > found any information confirming/dis-confirming that I can make HW ECC
> > > > and oob
> > > > tags work on our MLC nand.
> > >
> > > It is not so much a matter of HW or SW ECC, but how much space is unused.
> > > Some HW ECC schemes will leave enough unused OOB for tags and some will
> > > not.
> > >
> > > > Thanks,
> > > >
> > > > Boaz.
> > > >
> > > > On Mon, 2011-01-17 at 23:50 +0200, Boaz Ben-David wrote:
> > > > > From looking at the ecclayout on mxc_nd2.c there are only 4 bytes in
> > > > > the oobfree member. How many bytes does yaffs need to store it's
> > > > > tags? Also, the imx35 uses hw ecc, I've read that mlc nand+hw ecc
> > > > > usually means one cannot really use the oob for anything else, is
> > > > > that true?
> > > > >
> > > > > Boaz Ben-David <boaz.bd@wellsense-tech.com> wrote:
> > > > >
> > > > >
> > > > > I'm using freescale's iMX353 and the nand is Samsung 2GB MLC 4k page
> > > > > with 218 bytes oob. I was somehow under the impression that writing
> > > > > to the oob area in MLC nand is problematic and thats why I tried
> > > > > using the inband tags option. Isn't it?
> > > > >
> > > > > Charles Manning <manningc2@actrix.gen.nz> wrote:
> > > > >
> > > > > On Friday 14 January 2011 10:59:03 Ross Younger wrote:
> > > > > > On 13/01/11 17:35, Boaz Ben-David wrote:
> > > > > > > Well, thanks for everyone for their support.
> > > > > > > It turns out that all I had to do is mount the partitions with
> > > > > > > the -o inband-tags flag for YAFFS2 to work correctly on my NAND.
> > > > > >
> > > > > > Good to hear you've got it working. However, inband tags reduce
> > > > > > both the storage capacity of the NAND[0] and the performance you
> > > > > > can achieve[1]. I would recommend regular - out-of-band - tags if
> > > > > > possible.
> > > > > >
> > > > > > [0] by the size of the packed tags struct (16 bytes) per page;
> > > > > > about 0.8% of a device with 2k pages.
> > > > > >
> > > > > > [1] in cases where YAFFS wants to read only the tags of a page,
> > > > > > inband mode has to read in the entire page and throw away all but
> > > > > > the last 16 bytes. This adds up fast when mounting following an
> > > > > > unclean shutdown, when YAFFS has to scan the entire NAND.
> > > > >
> > > > > Yes, use out of band tags if you can. Inband tags will generally work
> > > > > even if the mtd driver's oob handling is broken so you're
> > > > > sidestepping the issue rather than fixing it.
> > > > >
> > > > > What NAND and NAND controller are you using?
> > > > >
> > > > > -- CHarles
> > > > >
> > > > > _______________________________________________
> > > > > yaffs mailing list
> > > > > yaffs@lists.aleph1.co.uk
> > > > > http://lists.aleph1.co.uk/cgi-bin/mailman/listinfo/yaffs
> > > >
> > > > _______________________________________________
> > > > yaffs mailing list
> > > > yaffs@lists.aleph1.co.uk
> > > > http://lists.aleph1.co.uk/cgi-bin/mailman/listinfo/yaffs
> >
> > _______________________________________________
> > yaffs mailing list
> > yaffs@lists.aleph1.co.uk
> > http://lists.aleph1.co.uk/cgi-bin/mailman/listinfo/yaffs
>
>
>
> _______________________________________________
> yaffs mailing list
> yaffs@lists.aleph1.co.uk
> http://lists.aleph1.co.uk/cgi-bin/mailman/listinfo/yaffs
(text/plain)