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Fix reference counting in pmap_ts_referenced() on RISC-V.

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pmap_ts_referenced() does not necessarily clear the access bit from
all accessed mappings of a given page.  Thus, if a scan of the mappings
needs to be restarted, we should be careful to avoid double-counting
accessed mappings whose access bits were not cleared in a previous
attempt.

Reported by:	alc
Reviewed by:	alc
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D20926
This commit is contained in:
Mark Johnston 2019-07-15 15:43:15 +00:00
parent e52acf6a46
commit 24074d28ec
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=350002
1 changed files with 13 additions and 10 deletions
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23
sys/riscv/riscv/pmap.c
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@ -3950,12 +3950,12 @@ pmap_ts_referenced(vm_page_t m)
pt_entry_t *l3, l3e;
vm_paddr_t pa;
vm_offset_t va;
int md_gen, pvh_gen, ret;
int cleared, md_gen, not_cleared, pvh_gen;
KASSERT((m->oflags & VPO_UNMANAGED) == 0,
("pmap_ts_referenced: page %p is not managed", m));
SLIST_INIT(&free);
ret = 0;
cleared = 0;
pa = VM_PAGE_TO_PHYS(m);
pvh = (m->flags & PG_FICTITIOUS) != 0 ? &pv_dummy : pa_to_pvh(pa);
@ -3963,6 +3963,7 @@ pmap_ts_referenced(vm_page_t m)
rw_rlock(&pvh_global_lock);
rw_wlock(lock);
retry:
not_cleared = 0;
if ((pvf = TAILQ_FIRST(&pvh->pv_list)) == NULL)
goto small_mappings;
pv = pvf;
@ -4013,8 +4014,9 @@ retry:
(l2e & PTE_SW_WIRED) == 0) {
pmap_clear_bits(l2, PTE_A);
pmap_invalidate_page(pmap, va);
}
ret++;
cleared++;
} else
not_cleared++;
}
PMAP_UNLOCK(pmap);
/* Rotate the PV list if it has more than one entry. */
@ -4023,7 +4025,7 @@ retry:
TAILQ_INSERT_TAIL(&pvh->pv_list, pv, pv_next);
pvh->pv_gen++;
}
if (ret >= PMAP_TS_REFERENCED_MAX)
if (cleared + not_cleared >= PMAP_TS_REFERENCED_MAX)
goto out;
} while ((pv = TAILQ_FIRST(&pvh->pv_list)) != pvf);
small_mappings:
@ -4062,8 +4064,9 @@ small_mappings:
*/
pmap_clear_bits(l3, PTE_A);
pmap_invalidate_page(pmap, pv->pv_va);
}
ret++;
cleared++;
} else
not_cleared++;
}
PMAP_UNLOCK(pmap);
/* Rotate the PV list if it has more than one entry. */
@ -4072,13 +4075,13 @@ small_mappings:
TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_next);
m->md.pv_gen++;
}
} while ((pv = TAILQ_FIRST(&m->md.pv_list)) != pvf && ret <
PMAP_TS_REFERENCED_MAX);
} while ((pv = TAILQ_FIRST(&m->md.pv_list)) != pvf && cleared +
not_cleared < PMAP_TS_REFERENCED_MAX);
out:
rw_wunlock(lock);
rw_runlock(&pvh_global_lock);
vm_page_free_pages_toq(&free, false);
return (ret);
return (cleared + not_cleared);
}
/*