On Tue, 28 Nov 2006 11:47:57 -0800 Randy Dunlap wrote: > On Sun, 19 Nov 2006 17:32:11 -0500 Jeff Mahoney wrote: > > > -----BEGIN PGP SIGNED MESSAGE----- > > Hash: SHA1 > > > > Al Viro wrote: > > > On Sun, Nov 19, 2006 at 11:04:33AM -0800, Randy Dunlap wrote: > > >> Andi Kleen wrote: > > >>>>> I would copy a relatively simple C implementation, like > > >>>>> arch/h8300/lib/checksum.c > > >>>> As long as the h8300 version has the same output as the x86 version. > > >>> The trouble is that the different architecture have different output > > >>> for csum_partial. So you already got a bug when someone wants to move > > >>> file systems. > > >>> > > >>> -Andi > > >> That argues for having only one version of it (in a lib.; my preference) > > >> -or- Every module having its own local copy/version of it. :( > > > > > > Wrong. csum_partial() result is defined modulo 0xffff and it's basically > > > "whatever's convenient as intermediate for this architecture". > > > > > > reiserfs use of it is just plain broken. net/* is fine, since all > > > final uses are via csum_fold() or equivalents. > > > > > > Note that reiserfs use is broken in another way: it takes fixed-endian > > > value > > > and feeds it to cpu_to_le32(). IOW, even if everything had literally the > > > same csum_partial(), the value it shits on disk would be endian-dependent. > > > > Oh great. Even better. :( > > Even more: MD/raid (=m) is broken in this way also. > It uses csum_partial(), which isn't present (CONFIG_NET=n). > > Kernel: arch/x86_64/boot/bzImage is ready (#9) > Building modules, stage 2. > MODPOST 101 modules > WARNING: "csum_partial" [drivers/md/md-mod.ko] undefined! > make[1]: *** [__modpost] Error 1 > make: *** [modules] Error 2 > > CONFIG_MD=y > CONFIG_BLK_DEV_MD=m > CONFIG_MD_LINEAR=m > # CONFIG_MD_RAID0 is not set > CONFIG_MD_RAID1=m > # CONFIG_MD_RAID10 is not set > # CONFIG_MD_RAID456 is not set > CONFIG_MD_MULTIPATH=m > # CONFIG_MD_FAULTY is not set > CONFIG_BLK_DEV_DM=y > CONFIG_DM_DEBUG=y > CONFIG_DM_CRYPT=m > CONFIG_DM_SNAPSHOT=y > CONFIG_DM_MIRROR=y > CONFIG_DM_ZERO=m > CONFIG_DM_MULTIPATH=y > CONFIG_DM_MULTIPATH_EMC=m > > --- > ~Randy > full broken config for MD: > http://oss.oracle.com/~rdunlap/configs/config-md-csum
Ingo, Neil: Al has summarized that csum_partial() is arch-specific. However, drivers/md/md.c uses it. Does that mean that RAID volumes are not portable across (some) architectures? Should md.c use a specific, known, fixed (as in static, arch-independent) version of csum_partial()? Will changing now possibly make some existing volumes non-portable? Thanks, --- ~Randy - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
