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 - To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
