On Tue, May 15, 2012 at 06:03:49PM +1000, NeilBrown wrote:
> On Tue, 15 May 2012 16:00:25 +0800 Yuanhan Liu <yuanhan.liu@xxxxxxxxxxxxxxx>
> wrote:
>
> > The code does nothing but repating assigning sb->sb_csum with original
> > value.
>
> This code sets the sb_csum to 0 while the csum is calculated.
>
> Without this, calculating the csum, setting it, then calculating again would
> produce a different result.
>
> So the code is correct as is.
Aha, got it. And sorry for the wrong patch.
Thanks,
Yuanhan Liu
>
> Thanks,
> NeilBrown
>
>
> >
> > Signed-off-by: Yuanhan Liu <yuanhan.liu@xxxxxxxxxxxxxxx>
> > ---
> > drivers/md/md.c | 4 ----
> > 1 files changed, 0 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index 0bd44e3..f2d799a 100644
> > --- a/drivers/md/md.c
> > +++ b/drivers/md/md.c
> > @@ -1439,15 +1439,12 @@ super_90_rdev_size_change(struct md_rdev *rdev, sector_t num_sectors)
> >
> > static __le32 calc_sb_1_csum(struct mdp_superblock_1 * sb)
> > {
> > - __le32 disk_csum;
> > u32 csum;
> > unsigned long long newcsum;
> > int size = 256 + le32_to_cpu(sb->max_dev)*2;
> > __le32 *isuper = (__le32*)sb;
> > int i;
> >
> > - disk_csum = sb->sb_csum;
> > - sb->sb_csum = 0;
> > newcsum = 0;
> > for (i=0; size>=4; size -= 4 )
> > newcsum += le32_to_cpu(*isuper++);
> > @@ -1456,7 +1453,6 @@ static __le32 calc_sb_1_csum(struct mdp_superblock_1 * sb)
> > newcsum += le16_to_cpu(*(__le16*) isuper);
> >
> > csum = (newcsum & 0xffffffff) + (newcsum >> 32);
> > - sb->sb_csum = disk_csum;
> > return cpu_to_le32(csum);
> > }
> >
>
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