From: Andreas Gruenbacher Date: Fri, 17 May 2019 18:18:43 +0000 (+0100) Subject: gfs2: Fix sign extension bug in gfs2_update_stats X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=11db0310d31de4deb24d06af043ae75d99d938ba;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git gfs2: Fix sign extension bug in gfs2_update_stats commit 5a5ec83d6ac974b12085cd99b196795f14079037 upstream. Commit 4d207133e9c3 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: 4d207133e9c3 ("gfs2: Make statistics unsigned, suitable for use with do_div()") Signed-off-by: Andreas Gruenbacher Cc: stable@vger.kernel.org # v4.4+ Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c index 65f33a0ac190..6f5c033fe4b5 100644 --- a/fs/gfs2/lock_dlm.c +++ b/fs/gfs2/lock_dlm.c @@ -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; } /**