On Tue, Nov 13, 2007 at 04:35:40PM +1100, Timothy Shimmin wrote:
> David Chinner wrote:
> > Perhaps we should look at cleaning up the cusers of offtoc, offtoct, etc
> > and killing BPCSHIFT altogether....
> >
> Yeah, I had a quick look before, but I will look closer again ;-)
>
> > egrep -Ir 'offtoc|ctoooff' . | egrep -v "anot|tag"
> ./linux-2.6/xfs_lrw.c:
> ctooff(offtoct(*offset)),
> ./linux-2.6/xfs_lrw.c: ctooff(offtoct(pos)),
> -1);
> ./linux-2.6/xfs_lrw.c: ctooff(offtoct(pos)),
> ./linux-2.6/xfs_linux.h:#define offtoc(x)
> (((__uint64_t)(x)+(NBPC-1))>>BPCSHIFT)
> ./linux-2.6/xfs_linux.h:#define offtoct(x) ((xfs_off_t)(x)>>BPCSHIFT)
> ./xfs_vnodeops.c: ctooff(offtoct(ioffset)), -1);
> ./xfs_vnodeops.c: ctooff(offtoct(ioffset)),
>
> So we basically just use:
>
> ctooff(offtoct(pos))
>
> where
> #define ctooff(x) ((xfs_off_t)(x)<<BPCSHIFT)
> #define offtoct(x) ((xfs_off_t)(x)>>BPCSHIFT)
> #define BPCSHIFT PAGE_SHIFT /* LOG2(NBPC) if exact */
>
> seems basically to be a:
>
> #define round_down_page(x) ((x) & ~(PAGE_SIZE - 1))
>
> or just use a
> round_down(x, PAGE_SIZE)
> and
> define the round_down for size which is power of 2.
>
> Like in asm-x86_64/proto.h
> #define round_up(x,y) (((x) + (y) - 1) & ~((y)-1))
> #define round_down(x,y) ((x) & ~((y)-1))
>
> What way do you reckon?
Neither ;)
Just replace them with (val & PAGE_CACHE_MASK)
Actually, the code in xfs_vnodeops.c culd probably just be removed; the
ioffset variable is already rounded to a multiple of page size....
Cheers,
dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group
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