On Wed, 2009-08-12 at 17:47 -0700, Amit Gud wrote:
> This patch modifies parsing of mount options to allows passing units
> along with the options. Valid units are "s" for seconds and "ms" for
> milliseconds. When not specified, the unit defaults to seconds.
>
> For example, "-o acdirmin=20ms" can be specified for 20 milliseconds,
> and "-o acdirmin=3s" or just "-o acdirmin=3" for 3 seconds.
>
> This code also changes the display of options in /proc/<pid>/mountstats
> from seconds to milliseconds to reflect the accuracy.
This won't work. Suddenly the contents of /proc/self/mountinfo can no
longer be used as intended because acdirmin/max/... are being displayed
in milliseconds, whereas the default unit is in seconds.
Furthermore, you'll have rounding errors when converting backwards and
forwards into HZ, since the latter is usually > 1ms.
I agree with Neil. I think it would be better to use a 3 decimal fixed
point notation instead. Couldn't something like the following be made to
work?
static int nfs_parse_mstimeo(const char *str, unsigned long *res)
{
unsigned int msecs;
char *str2;
msecs = (unsigned int)simple_strtoul(str, &str2, 10);
msecs *= 1000;
/* Check if we're being given fixed point decimal notation */
if (*str2 == '.') {
unsigned long m;
size_t ndec = strlen(++str2);
/* Disallow more than 1/1000 precision */
if (ndec > 3)
goto out_inval;
if (strict_strtoul(str2, 10, &m))
goto out_inval;
switch (ndec) {
case 1:
m *= 10;
case 2:
m *= 10;
break;
}
msecs += (unsigned int)m;
} else if (*str2 != '\0' || str2 == str)
goto out_inval;
*res = msecs_to_jiffies(msecs);
return 0;
out_inval:
return -EINVAL;
}
static void nfs_display_mstimeo(struct seq_file *m, unsigned long val)
{
unsigned int msec = jiffies_to_msecs(val);
unsigned int rem = msec % 1000;
seq_printf(m, "%u", msec / 1000);
if (rem != 0)
seq_printf(m, ".%.3u", rem);
}
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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