On Tue, 2013-08-13 at 19:52 +0000, Adamson, Dros wrote:
> I think I was the last one to touch this.
>
> On Aug 13, 2013, at 2:35 PM, Trond Myklebust <Trond.Myklebust@xxxxxxxxxx> wrote:
>
> > We want to be able to display the crc32 hash of the filehandle in
> > tracepoints.
> >
> > Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
> > ---
> > fs/nfs/inode.c | 3 +--
> > fs/nfs/internal.h | 20 ++++++++++++++++++++
> > 2 files changed, 21 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
> > index af6e806..9a98b04 100644
> > --- a/fs/nfs/inode.c
> > +++ b/fs/nfs/inode.c
> > @@ -38,7 +38,6 @@
> > #include <linux/slab.h>
> > #include <linux/compat.h>
> > #include <linux/freezer.h>
> > -#include <linux/crc32.h>
> >
> > #include <asm/uaccess.h>
> >
> > @@ -1190,7 +1189,7 @@ u32 _nfs_display_fhandle_hash(const struct nfs_fh *fh)
> > {
> > /* wireshark uses 32-bit AUTODIN crc and does a bitwise
> > * not on the result */
> > - return ~crc32(0xFFFFFFFF, &fh->data[0], fh->size);
> > + return nfs_fhandle_hash(fh);
> > }
> >
> > /*
> > diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
> > index 9b694f1..50f7068 100644
> > --- a/fs/nfs/internal.h
> > +++ b/fs/nfs/internal.h
> > @@ -5,6 +5,7 @@
> > #include "nfs4_fs.h"
> > #include <linux/mount.h>
> > #include <linux/security.h>
> > +#include <linux/crc32.h>
> >
> > #define NFS_MS_MASK (MS_RDONLY|MS_NOSUID|MS_NODEV|MS_NOEXEC|MS_SYNCHRONOUS)
> >
> > @@ -574,3 +575,22 @@ u64 nfs_timespec_to_change_attr(const struct timespec *ts)
> > {
> > return ((u64)ts->tv_sec << 30) + ts->tv_nsec;
> > }
> > +
> > +#ifdef CONFIG_CRC32
>
> Good catch!
>
> > +/**
> > + * nfs_fhandle_hash - calculate the crc32 hash for the filehandle
> > + * @fh - pointer to filehandle
> > + *
> > + * returns a crc32 hash for the filehandle that is compatible with
> > + * the one displayed by "wireshark".
> > + */
> > +static inline u32 nfs_fhandle_hash(const struct nfs_fh *fh)
> > +{
> > + return ~crc32_le(0xFFFFFFFF, &fh->data[0], fh->size);
>
> Why the change to crc32_le? Is that what wireshark does? I don't remember exactly what I found when I looked at how wireshark made FH hashes.
>
> -dros
If you look inside include/linux/crc32.h, you'll see that crc32 is just
a macro that expands to a call to the function crc32_le(). So all I've
done is to expand the macro.
Cheers
Trond
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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