On Wed, 2014-12-10 at 17:32 +0100, Rasmus Villemoes wrote:
> Relying on the sign (after casting to int) of the difference of two
> quantities for comparison is usually wrong. For example, should a-b
> turn out to be 2^31, the return value of cmp(a,b) is -2^31; but that
> would also be the return value from cmp(b, a). So a compares less than
> b and b compares less than a. One can also easily find three values
> a,b,c such that a compares less than b, b compares less than c, but a
> does not compare less than c.
>
Looks good for me. Thank you for the fix.
Reviewed-by: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
Thanks,
Vyacheslav Dubeyko.
> Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
> ---
> fs/hfs/catalog.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/fs/hfs/catalog.c b/fs/hfs/catalog.c
> index ff0316b925a5..db458ee3a546 100644
> --- a/fs/hfs/catalog.c
> +++ b/fs/hfs/catalog.c
> @@ -162,14 +162,16 @@ err2:
> */
> int hfs_cat_keycmp(const btree_key *key1, const btree_key *key2)
> {
> - int retval;
> + __be32 k1p, k2p;
>
> - retval = be32_to_cpu(key1->cat.ParID) - be32_to_cpu(key2->cat.ParID);
> - if (!retval)
> - retval = hfs_strcmp(key1->cat.CName.name, key1->cat.CName.len,
> - key2->cat.CName.name, key2->cat.CName.len);
> + k1p = key1->cat.ParID;
> + k2p = key2->cat.ParID;
>
> - return retval;
> + if (k1p != k2p)
> + return be32_to_cpu(k1p) < be32_to_cpu(k2p) ? -1 : 1;
> +
> + return hfs_strcmp(key1->cat.CName.name, key1->cat.CName.len,
> + key2->cat.CName.name, key2->cat.CName.len);
> }
>
> /* Try to get a catalog entry for given catalog id */
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