[PATCH] UBI: only read UBI_VID_HDR_SIZE when reading the vid_hdr

[Sascha Hauer]

On Thu, Jun 23, 2016 at 04:38:25PM +0200, Richard Weinberger wrote:
> Am 23.06.2016 um 15:29 schrieb Sascha Hauer:
> > When reading the vid hdr from the device UBI always reads a whole
> > page. Instead, read only the data we actually need and speed up
> > attachment of UBI devices by potentially making use of reading
> > subpages.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
> > ---
> > 
> > Please review carefully. It obviously works and speeds up UBI attachment
> > from 3s to 2s here in one case and I have not found places where this patch
> > makes problems, but there might be a reason I haven't seen why in case of
> > the ec header only the header is read while in case of the vid header the
> > whole page is read.
> > 
> >  drivers/mtd/ubi/io.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
> > index 10cf3b5..31918a0 100644
> > --- a/drivers/mtd/ubi/io.c
> > +++ b/drivers/mtd/ubi/io.c
> > @@ -1019,7 +1019,7 @@ int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
> >  
> >  	p = (char *)vid_hdr - ubi->vid_hdr_shift;
> >  	read_err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
> > -			  ubi->vid_hdr_alsize);
> > +			  UBI_VID_HDR_SIZE);
> 
> Hmm, I fear this will break as soon ubi->vid_hdr_shift is non-zero.

Ok, just tried and indeed it does break. Would it be an option to read
UBI_VID_HDR_SIZE + ubi->vid_hdr_shift bytes instead?


Sascha

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