time: jiffies_delta_to_clock_t() helper to the rescue

time: jiffies_delta_to_clock_t() helper to the rescue

Various /proc/net files sometimes report crazy timer values, expressed
in clock_t units.

This happens when an expired timer delta (expires - jiffies) is passed
to jiffies_to_clock_t().

This function has an overflow in :

return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);

commit cbbc719fccdb8cb (time: Change jiffies_to_clock_t() argument type
to unsigned long) only got around the problem.

As we cant output negative values in /proc/net/tcp without breaking
various tools, I suggest adding a jiffies_delta_to_clock_t() wrapper
that caps the negative delta to a 0 value.

Signed-off-by: Eric Dumazet <[email protected]>
Reported-by: Maciej Żenczykowski <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Paul Gortmaker <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: hank <[email protected]>
Signed-off-by: David S. Miller <[email protected]>