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libdm: check non-zero io count in _average_{rd,wr}_wait_time (Coverity)

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Although a non-zero value for the number of ticks spent doing IO
should imply a non-zero number of IOs in the interval test for
this explicitly to avoid a divide-by-zero in the event of bad
counter data.
This commit is contained in:
Bryn M. Reeves 2016-07-06 09:20:05 +01:00
parent 03e03e9c11
commit 95ef0cdb46
1 changed files with 12 additions and 3 deletions
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15
libdm/libdm-stats.c
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@ -2600,11 +2600,15 @@ static int _average_rd_wait_time(const struct dm_stats *dms, double *await,
rd_io_ticks = dm_stats_get_counter(dms, DM_STATS_READ_NSECS,
region_id, area_id);
nr_rd_ios = dm_stats_get_counter(dms, DM_STATS_READS_COUNT,
region_id, area_id);
if (rd_io_ticks > 0)
/*
* If rd_io_ticks is > 0 this should imply that nr_rd_ios is
* also > 0 (unless a kernel bug exists). Test for both here
* before using the IO count as a divisor (Coverity).
*/
if (rd_io_ticks > 0 && nr_rd_ios > 0)
*await = (double) rd_io_ticks / (double) nr_rd_ios;
else
*await = 0.0;
@ -2622,7 +2626,12 @@ static int _average_wr_wait_time(const struct dm_stats *dms, double *await,
nr_wr_ios = dm_stats_get_counter(dms, DM_STATS_WRITES_COUNT,
region_id, area_id);
if (wr_io_ticks > 0)
/*
* If wr_io_ticks is > 0 this should imply that nr_wr_ios is
* also > 0 (unless a kernel bug exists). Test for both here
* before using the IO count as a divisor (Coverity).
*/
if (wr_io_ticks > 0 && nr_wr_ios > 0)
*await = (double) wr_io_ticks / (double) nr_wr_ios;
else
*await = 0.0;