> If a DAMOS scheme has a damos_quota_goal of zero target_value,
> damos_quota_goal() could trigger division-by-zero error. Hence each
> DAMON API callers should do the zero target_value validation. It is
> easy to make mistakes. Actually such bugs in DAMON_LRU_SORT and
> DAMON_SAMPLE_MTIER were found and fixed [1].
>
> It is better to handle the corner case only once in the core layer,
> instead of multiple places in all DAMON API callers. One
> straightforward option is using an alternative denominator for the
> corner case in the damos_quota_goal(). However, the zero target_value
> is meaningless. In this case, the quota goal is always evaluated as
> achieved or over-achieved. The quota will only keep being reduced.
>
> Simply avoid using zero target_value by adding a check in the core layer
> DAMOS quota goal parameters validation/commit path,
> damos_commit_quota_goal(). Update it to return an error in the case.
> Also update its caller to propagate the error.
>
> [1] https://lore.kernel.org/[email protected]
>
> Signed-off-by: SJ Park <[email protected]>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=1
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