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
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