The following changes since commit 6f9cdcfcc7598c7d7b19c4a5120a251a80dab183: iolog: don't truncate time values (2023-10-02 14:29:29 +0000) are available in the Git repository at: git://git.kernel.dk/fio.git master for you to fetch changes up to 16b9f29dab1d105951da663474ec243942fda400: Merge branch 'fix-stat-overflow' of https://github.com/stilor/fio (2023-10-06 15:27:23 -0400) ---------------------------------------------------------------- Alexey Neyman (2): Change memcpy() calls to assignments Handle 32-bit overflows in disk utilization stats Vincent Fu (1): Merge branch 'fix-stat-overflow' of https://github.com/stilor/fio diskutil.c | 30 ++++++++++++++++++++++++------ 1 file changed, 24 insertions(+), 6 deletions(-) --- Diff of recent changes: diff --git a/diskutil.c b/diskutil.c index cf4ede85..69b3dd26 100644 --- a/diskutil.c +++ b/diskutil.c @@ -77,6 +77,23 @@ static int get_io_ticks(struct disk_util *du, struct disk_util_stat *dus) return ret != 10; } +static uint64_t safe_32bit_diff(uint64_t nval, uint64_t oval) +{ + /* Linux kernel prints some of the stat fields as 32-bit integers. It is + * possible that the value overflows, but since fio uses unsigned 64-bit + * arithmetic in update_io_tick_disk(), it instead results in a huge + * bogus value being added to the respective accumulating field. Just + * in case Linux starts reporting these metrics as 64-bit values in the + * future, check that overflow actually happens around the 32-bit + * unsigned boundary; assume overflow only happens once between + * successive polls. + */ + if (oval <= nval || oval >= (1ull << 32)) + return nval - oval; + else + return (1ull << 32) + nval - oval; +} + static void update_io_tick_disk(struct disk_util *du) { struct disk_util_stat __dus, *dus, *ldus; @@ -96,15 +113,16 @@ static void update_io_tick_disk(struct disk_util *du) dus->s.ios[1] += (__dus.s.ios[1] - ldus->s.ios[1]); dus->s.merges[0] += (__dus.s.merges[0] - ldus->s.merges[0]); dus->s.merges[1] += (__dus.s.merges[1] - ldus->s.merges[1]); - dus->s.ticks[0] += (__dus.s.ticks[0] - ldus->s.ticks[0]); - dus->s.ticks[1] += (__dus.s.ticks[1] - ldus->s.ticks[1]); - dus->s.io_ticks += (__dus.s.io_ticks - ldus->s.io_ticks); - dus->s.time_in_queue += (__dus.s.time_in_queue - ldus->s.time_in_queue); + dus->s.ticks[0] += safe_32bit_diff(__dus.s.ticks[0], ldus->s.ticks[0]); + dus->s.ticks[1] += safe_32bit_diff(__dus.s.ticks[1], ldus->s.ticks[1]); + dus->s.io_ticks += safe_32bit_diff(__dus.s.io_ticks, ldus->s.io_ticks); + dus->s.time_in_queue += + safe_32bit_diff(__dus.s.time_in_queue, ldus->s.time_in_queue); fio_gettime(&t, NULL); dus->s.msec += mtime_since(&du->time, &t); - memcpy(&du->time, &t, sizeof(t)); - memcpy(&ldus->s, &__dus.s, sizeof(__dus.s)); + du->time = t; + ldus->s = __dus.s; } int update_io_ticks(void)
