mm/damon/vaddr: support stat-purpose DAMOS filters

This patch extends DAMOS_STAT handling of the DAMON operations sets for
virtual address spaces for ops-level DAMOS filters.  It leverages the
walk_page_range to walk the page table and gets the folio from page table.
The last folio scanned is stored in damos->last_applied to prevent double
counting.

Link: https://lkml.kernel.org/r/264a4b5ea202fd73c01b349c9694d8bf9978c441.1754135312.git.pyyjason@gmail.com
Signed-off-by: Yueyang Pan <pyyjason@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Usama Arif <usamaarif642@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 87e825349bdf4c98837591c77784be903ceae7eb..66ef9869eafe1100ead64aaaa8ac4195497cdeb7 100644 (file)
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -890,6 +890,107 @@ free_lists:
        return applied * PAGE_SIZE;
 }
 
+struct damos_va_stat_private {
+       struct damos *scheme;
+       unsigned long *sz_filter_passed;
+};
+
+static inline bool damos_va_invalid_folio(struct folio *folio,
+               struct damos *s)
+{
+       return !folio || folio == s->last_applied;
+}
+
+static int damos_va_stat_pmd_entry(pmd_t *pmd, unsigned long addr,
+               unsigned long next, struct mm_walk *walk)
+{
+       struct damos_va_stat_private *priv = walk->private;
+       struct damos *s = priv->scheme;
+       unsigned long *sz_filter_passed = priv->sz_filter_passed;
+       struct vm_area_struct *vma = walk->vma;
+       struct folio *folio;
+       spinlock_t *ptl;
+       pte_t *start_pte, *pte, ptent;
+       int nr;
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+       if (pmd_trans_huge(*pmd)) {
+               pmd_t pmde;
+
+               ptl = pmd_trans_huge_lock(pmd, vma);
+               if (!ptl)
+                       return 0;
+               pmde = pmdp_get(pmd);
+               if (!pmd_present(pmde))
+                       goto huge_unlock;
+
+               folio = vm_normal_folio_pmd(vma, addr, pmde);
+
+               if (damos_va_invalid_folio(folio, s))
+                       goto huge_unlock;
+
+               if (!damos_va_filter_out(s, folio, vma, addr, NULL, pmd))
+                       *sz_filter_passed += folio_size(folio);
+               s->last_applied = folio;
+
+huge_unlock:
+               spin_unlock(ptl);
+               return 0;
+       }
+#endif
+       start_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+       if (!start_pte)
+               return 0;
+
+       for (; addr < next; pte += nr, addr += nr * PAGE_SIZE) {
+               nr = 1;
+               ptent = ptep_get(pte);
+
+               if (pte_none(ptent) || !pte_present(ptent))
+                       continue;
+
+               folio = vm_normal_folio(vma, addr, ptent);
+
+               if (damos_va_invalid_folio(folio, s))
+                       continue;
+
+               if (!damos_va_filter_out(s, folio, vma, addr, pte, NULL))
+                       *sz_filter_passed += folio_size(folio);
+               nr = folio_nr_pages(folio);
+               s->last_applied = folio;
+       }
+       pte_unmap_unlock(start_pte, ptl);
+       return 0;
+}
+
+static unsigned long damos_va_stat(struct damon_target *target,
+               struct damon_region *r, struct damos *s,
+               unsigned long *sz_filter_passed)
+{
+       struct damos_va_stat_private priv;
+       struct mm_struct *mm;
+       struct mm_walk_ops walk_ops = {
+               .pmd_entry = damos_va_stat_pmd_entry,
+               .walk_lock = PGWALK_RDLOCK,
+       };
+
+       priv.scheme = s;
+       priv.sz_filter_passed = sz_filter_passed;
+
+       if (!damos_ops_has_filter(s))
+               return 0;
+
+       mm = damon_get_mm(target);
+       if (!mm)
+               return 0;
+
+       mmap_read_lock(mm);
+       walk_page_range(mm, r->ar.start, r->ar.end, &walk_ops, &priv);
+       mmap_read_unlock(mm);
+       mmput(mm);
+       return 0;
+}
+
 static unsigned long damon_va_apply_scheme(struct damon_ctx *ctx,
                struct damon_target *t, struct damon_region *r,
                struct damos *scheme, unsigned long *sz_filter_passed)
@@ -916,7 +1017,7 @@ static unsigned long damon_va_apply_scheme(struct damon_ctx *ctx,
        case DAMOS_MIGRATE_COLD:
                return damos_va_migrate(t, r, scheme, sz_filter_passed);
        case DAMOS_STAT:
-               return 0;
+               return damos_va_stat(t, r, scheme, sz_filter_passed);
        default:
                /*
                 * DAMOS actions that are not yet supported by 'vaddr'.