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When calculating the hotness of each region for the under-quota regions
prioritization, DAMON divides some values by the maximum nr_accesses.
However, due to the type of the related variables, simple division-based
calculation of the divisor can return zero. As a result, divide-by-zero
is possible. Fix it by using damon_max_nr_accesses(), which handles the
case.
Link: https://lkml.kernel.org/r/20231019194924.100347-4-sj@kernel.org
Fixes: 198f0f4c58 ("mm/damon/vaddr,paddr: support pageout prioritization")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Jakub Acs <acsjakub@amazon.de>
Cc: <stable@vger.kernel.org> [5.16+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
122 lines
3.0 KiB
C
122 lines
3.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Common Primitives for Data Access Monitoring
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*
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* Author: SeongJae Park <sj@kernel.org>
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*/
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#include <linux/mmu_notifier.h>
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#include <linux/page_idle.h>
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#include <linux/pagemap.h>
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#include <linux/rmap.h>
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#include "ops-common.h"
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/*
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* Get an online page for a pfn if it's in the LRU list. Otherwise, returns
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* NULL.
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*
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* The body of this function is stolen from the 'page_idle_get_folio()'. We
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* steal rather than reuse it because the code is quite simple.
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*/
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struct folio *damon_get_folio(unsigned long pfn)
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{
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struct page *page = pfn_to_online_page(pfn);
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struct folio *folio;
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if (!page || PageTail(page))
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return NULL;
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folio = page_folio(page);
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if (!folio_test_lru(folio) || !folio_try_get(folio))
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return NULL;
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if (unlikely(page_folio(page) != folio || !folio_test_lru(folio))) {
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folio_put(folio);
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folio = NULL;
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}
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return folio;
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}
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void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr)
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{
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struct folio *folio = damon_get_folio(pte_pfn(ptep_get(pte)));
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if (!folio)
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return;
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if (ptep_clear_young_notify(vma, addr, pte))
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folio_set_young(folio);
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folio_set_idle(folio);
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folio_put(folio);
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}
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void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr)
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{
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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struct folio *folio = damon_get_folio(pmd_pfn(pmdp_get(pmd)));
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if (!folio)
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return;
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if (pmdp_clear_young_notify(vma, addr, pmd))
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folio_set_young(folio);
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folio_set_idle(folio);
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folio_put(folio);
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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}
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#define DAMON_MAX_SUBSCORE (100)
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#define DAMON_MAX_AGE_IN_LOG (32)
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int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
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struct damos *s)
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{
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int freq_subscore;
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unsigned int age_in_sec;
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int age_in_log, age_subscore;
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unsigned int freq_weight = s->quota.weight_nr_accesses;
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unsigned int age_weight = s->quota.weight_age;
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int hotness;
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freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE /
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damon_max_nr_accesses(&c->attrs);
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age_in_sec = (unsigned long)r->age * c->attrs.aggr_interval / 1000000;
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for (age_in_log = 0; age_in_log < DAMON_MAX_AGE_IN_LOG && age_in_sec;
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age_in_log++, age_in_sec >>= 1)
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;
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/* If frequency is 0, higher age means it's colder */
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if (freq_subscore == 0)
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age_in_log *= -1;
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/*
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* Now age_in_log is in [-DAMON_MAX_AGE_IN_LOG, DAMON_MAX_AGE_IN_LOG].
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* Scale it to be in [0, 100] and set it as age subscore.
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*/
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age_in_log += DAMON_MAX_AGE_IN_LOG;
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age_subscore = age_in_log * DAMON_MAX_SUBSCORE /
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DAMON_MAX_AGE_IN_LOG / 2;
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hotness = (freq_weight * freq_subscore + age_weight * age_subscore);
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if (freq_weight + age_weight)
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hotness /= freq_weight + age_weight;
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/*
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* Transform it to fit in [0, DAMOS_MAX_SCORE]
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*/
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hotness = hotness * DAMOS_MAX_SCORE / DAMON_MAX_SUBSCORE;
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return hotness;
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}
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int damon_cold_score(struct damon_ctx *c, struct damon_region *r,
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struct damos *s)
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{
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int hotness = damon_hot_score(c, r, s);
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/* Return coldness of the region */
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return DAMOS_MAX_SCORE - hotness;
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}
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