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| author | Quanmin Yan <[email protected]> | 2025-08-21 12:55:55 +0000 |
|---|---|---|
| committer | Andrew Morton <[email protected]> | 2025-08-28 05:45:43 +0000 |
| commit | 9f68eabab9d9aaa764a8d234c4170119e6518102 (patch) | |
| tree | a0391b80733fdeb6741dff9bbf7791d7448fc481 /mm/sparse-vmemmap.c | |
| parent | kexec: add KEXEC_FILE_NO_CMA as a legal flag (diff) | |
| download | kernel-9f68eabab9d9aaa764a8d234c4170119e6518102.tar.gz kernel-9f68eabab9d9aaa764a8d234c4170119e6518102.zip | |
mm/damon/core: prevent unnecessary overflow in damos_set_effective_quota()
On 32-bit systems, the throughput calculation in
damos_set_effective_quota() is prone to unnecessary multiplication
overflow. Using mult_frac() to fix it.
Andrew Paniakin also recently found and privately reported this issue, on
64 bit systems. This can also happen on 64-bit systems, once the charged
size exceeds ~17 TiB. On systems running for long time in production,
this issue can actually happen.
More specifically, when a DAMOS scheme having the time quota run for
longtime, throughput calculation can overflow and set esz too small. As a
result, speed of the scheme get unexpectedly slow.
Link: https://lkml.kernel.org/r/[email protected]
Fixes: 1cd243030059 ("mm/damon/schemes: implement time quota")
Signed-off-by: Quanmin Yan <[email protected]>
Reported-by: Andrew Paniakin <[email protected]>
Reviewed-by: SeongJae Park <[email protected]>
Cc: Kefeng Wang <[email protected]>
Cc: ze zuo <[email protected]>
Cc: <[email protected]> [5.16+]
Signed-off-by: Andrew Morton <[email protected]>
Diffstat (limited to 'mm/sparse-vmemmap.c')
0 files changed, 0 insertions, 0 deletions