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Fix negative time overflows in DDT pruning #18886

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Fix negative time overflows in DDT pruning #18886

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11 changes: 7 additions & 4 deletions module/zfs/ddt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2868,7 +2868,8 @@ ddt_prune_walk(spa_t *spa, uint64_t cutoff, ddt_age_histo_t *histogram)

/* build a histogram */
if (histogram != NULL) {
uint64_t age = (now - class_start) / 3600;
uint64_t age = (class_start < now) ?
(now - class_start) / 3600 : 0;
int bin = MIN(highbit64(age), HIST_BINS - 1);
histogram->dah_entries++;
histogram->dah_age_histo[bin]++;
Expand Down Expand Up @@ -2922,10 +2923,10 @@ ddt_prune_unique_entries(spa_t *spa, zpool_ddt_prune_unit_t unit,
zfs_dbgmsg("prune %llu %s", (u_longlong_t)amount,
unit == ZPOOL_DDT_PRUNE_PERCENTAGE ? "%" : "seconds old or older");

uint64_t now = gethrestime_sec();
if (unit == ZPOOL_DDT_PRUNE_PERCENTAGE) {
ddt_age_histo_t histogram;
uint64_t oldest = 0;
uint64_t now = gethrestime_sec();

/* Make a pass over DDT to build a histogram */
ddt_prune_walk(spa, 0, &histogram);
Expand All @@ -2952,9 +2953,11 @@ ddt_prune_unique_entries(spa_t *spa, zpool_ddt_prune_unit_t unit,
if (ddt_dump_prune_histogram)
ddt_dump_age_histogram(&histogram, cutoff);
} else if (unit == ZPOOL_DDT_PRUNE_AGE) {
cutoff = gethrestime_sec() - amount;
if (amount >= now)
return (SET_ERROR(EINVAL));
cutoff = now - amount;
} else {
return (EINVAL);
return (SET_ERROR(EINVAL));
}

if (cutoff > 0 && !spa_shutting_down(spa) && !issig()) {
Expand Down
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