Re: [PATCH v2 7/8] xfs: Add xfs_log_rlimit.[c|h]

["Michael L. Semon" <mlsemon35@xxxxxxxxx>]

On 05/17/2013 01:39 AM, Jeff Liu wrote:
> From: Jie Liu <jeff.liu@xxxxxxxxxx>
>
> Add source files for xfs_log_rlimit.[c|h].
> The new source would be used for the log space validation.
Update:  To build the kernel, I'm getting by on a sysadmin hack that 
looks like this:
--- linux/fs/xfs/xfs_log_rlimit.c.orig  2013-05-17 03:36:28.983493357 -0400
+++ linux/fs/xfs/xfs_log_rlimit.c       2013-05-17 04:21:07.090661828 -0400
@@ -127,8 +127,10 @@
         * Also, the log size should be a multiple of the log stripe unit, round
         * it up to lsunit boundary if lsunit is specified.
         */
-       minlblks = lsunit ? (roundup(BTOBB(maxlres), lsunit) + 2 * lsunit) * 2 :
-                           BTOBB(maxlres) * 2;
+       minlblks = lsunit ?
+               (roundup((const int)(BTOBB(maxlres)), lsunit) +
+               2 * lsunit) * 2 :
+                       BTOBB(maxlres) * 2;

        if (log->l_logBBsize < minlblks) {
                xfs_crit(mp,

However, that makes no sense.  There is a roundup in <linux/kernel.h> 
that goes like this:
/* The `const' in roundup() prevents gcc-3.3 from calling __divdi3 */
#define roundup(x, y) (                                 \
{                                                       \
        const typeof(y) __y = y;                        \
        (((x) + (__y - 1)) / __y) * __y;                \
}                                                       \
)

Okay, so that gave me the inspiration to cast the type so gcc-4.8.0 
wouldn't call __divdi3.  But why did this make a difference?
Disclaimer:  I'm not a C macro guru, so I don't know which random 
sequence of punctuation keys would make roundup() happy.
Michael