gfs2: Fix sign extension bug in gfs2_update_stats (5a5ec83d) · Commits · 戴 / test

Commit changed the types of the statistic values in struct gfs2_lkstats from s64 to u64. Because of that, what should be a signed value in gfs2_update_stats turned into an unsigned value. When shifted right, we end up with a large positive value instead of a small negative value, which results in an incorrect variance estimate. Fixes: ("gfs2: Make statistics unsigned, suitable for use with do_div()") Signed-off-by:

Andreas Gruenbacher <agruenba@redhat.com> Cc: stable@vger.kernel.org # v4.4+

fs/gfs2/lock_dlm.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -31,9 +31,10 @@
		* @delta is the difference between the current rtt sample and the
		* running average srtt. We add 1/8 of that to the srtt in order to
		* update the current srtt estimate. The variance estimate is a bit
		* more complicated. We subtract the abs value of the @delta from
		* the current variance estimate and add 1/4 of that to the running
		* total.
		* more complicated. We subtract the current variance estimate from
		* the abs value of the @delta and add 1/4 of that to the running
		* total. That's equivalent to 3/4 of the current variance
		* estimate plus 1/4 of the abs of @delta.
		*
		* Note that the index points at the array entry containing the smoothed
		* mean value, and the variance is always in the following entry
		@@ -49,7 +50,7 @@ static inline void gfs2_update_stats(struct gfs2_lkstats *s, unsigned index,
		s64 delta = sample - s->stats[index];
		s->stats[index] += (delta >> 3);
		index++;
		s->stats[index] += ((abs(delta) - s->stats[index]) >> 2);
		s->stats[index] += (s64)(abs(delta) - s->stats[index]) >> 2;
		}

		/**

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