mm/damon: avoid applying DAMOS action to same entity multiple times

'paddr' DAMON operations set can apply a DAMOS scheme's action to a large
folio multiple times in single DAMOS-regions-walk if the folio is laid on
multiple DAMON regions.  Add a field for DAMOS scheme object that can be
used by the underlying ops to know what was the last entity that the
scheme's action has applied.  The core layer unsets the field when each
DAMOS-regions-walk is done for the given scheme.  And update 'paddr' ops
to use the infrastructure to avoid the problem.

Link: https://lkml.kernel.org/r/20250207212033.45269-3-sj@kernel.org
Fixes: 57223ac29584 ("mm/damon/paddr: support the pageout scheme")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Usama Arif <usamaarif642@gmail.com>
Closes: https://lore.kernel.org/20250203225604.44742-3-usamaarif642@gmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/damon.h b/include/linux/damon.h
index c9074d569596a667bfce342e2affe82041df35e9..b4d37d9b92212e8ba9006a91b34116b1672f4a4e 100644 (file)
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -432,6 +432,7 @@ struct damos_access_pattern {
  * @wmarks:            Watermarks for automated (in)activation of this scheme.
  * @target_nid:                Destination node if @action is "migrate_{hot,cold}".
  * @filters:           Additional set of &struct damos_filter for &action.
+ * @last_applied:      Last @action applied ops-managing entity.
  * @stat:              Statistics of this scheme.
  * @list:              List head for siblings.
  *
@@ -454,6 +455,15 @@ struct damos_access_pattern {
  * implementation could check pages of the region and skip &action to respect
  * &filters
  *
+ * The minimum entity that @action can be applied depends on the underlying
+ * &struct damon_operations.  Since it may not be aligned with the core layer
+ * abstract, namely &struct damon_region, &struct damon_operations could apply
+ * @action to same entity multiple times.  Large folios that underlying on
+ * multiple &struct damon region objects could be such examples.  The &struct
+ * damon_operations can use @last_applied to avoid that.  DAMOS core logic
+ * unsets @last_applied when each regions walking for applying the scheme is
+ * finished.
+ *
  * After applying the &action to each region, &stat_count and &stat_sz is
  * updated to reflect the number of regions and total size of regions that the
  * &action is applied.
@@ -482,6 +492,7 @@ struct damos {
                int target_nid;
        };
        struct list_head filters;
+       void *last_applied;
        struct damos_stat stat;
        struct list_head list;
 };

diff --git a/mm/damon/core.c b/mm/damon/core.c
index 384935ef4e65e63b51f9edef44ac62dc79e52438..dc8f94fe7c3bc816f796f5f3d06108caf8e6c84b 100644 (file)
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1856,6 +1856,7 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
                s->next_apply_sis = c->passed_sample_intervals +
                        (s->apply_interval_us ? s->apply_interval_us :
                         c->attrs.aggr_interval) / sample_interval;
+               s->last_applied = NULL;
        }
 }
 

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 2ac19ebc707664762db451bbfcdc59749256937b..eb10a723b0a73e34de82652d27339771d6fc0ab6 100644 (file)
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -254,6 +254,17 @@ static bool damos_pa_filter_out(struct damos *scheme, struct folio *folio)
        return false;
 }
 
+static bool damon_pa_invalid_damos_folio(struct folio *folio, struct damos *s)
+{
+       if (!folio)
+               return true;
+       if (folio == s->last_applied) {
+               folio_put(folio);
+               return true;
+       }
+       return false;
+}
+
 static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s,
                unsigned long *sz_filter_passed)
 {
@@ -261,6 +272,7 @@ static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s,
        LIST_HEAD(folio_list);
        bool install_young_filter = true;
        struct damos_filter *filter;
+       struct folio *folio;
 
        /* check access in page level again by default */
        damos_for_each_filter(filter, s) {
@@ -279,9 +291,8 @@ static unsigned long damon_pa_pageout(struct damon_region *r, struct damos *s,
 
        addr = r->ar.start;
        while (addr < r->ar.end) {
-               struct folio *folio = damon_get_folio(PHYS_PFN(addr));
-
-               if (!folio) {
+               folio = damon_get_folio(PHYS_PFN(addr));
+               if (damon_pa_invalid_damos_folio(folio, s)) {
                        addr += PAGE_SIZE;
                        continue;
                }
@@ -307,6 +318,7 @@ put_folio:
                damos_destroy_filter(filter);
        applied = reclaim_pages(&folio_list);
        cond_resched();
+       s->last_applied = folio;
        return applied * PAGE_SIZE;
 }
 
@@ -315,12 +327,12 @@ static inline unsigned long damon_pa_mark_accessed_or_deactivate(
                unsigned long *sz_filter_passed)
 {
        unsigned long addr, applied = 0;
+       struct folio *folio;
 
        addr = r->ar.start;
        while (addr < r->ar.end) {
-               struct folio *folio = damon_get_folio(PHYS_PFN(addr));
-
-               if (!folio) {
+               folio = damon_get_folio(PHYS_PFN(addr));
+               if (damon_pa_invalid_damos_folio(folio, s)) {
                        addr += PAGE_SIZE;
                        continue;
                }
@@ -339,6 +351,7 @@ put_folio:
                addr += folio_size(folio);
                folio_put(folio);
        }
+       s->last_applied = folio;
        return applied * PAGE_SIZE;
 }
 
@@ -482,12 +495,12 @@ static unsigned long damon_pa_migrate(struct damon_region *r, struct damos *s,
 {
        unsigned long addr, applied;
        LIST_HEAD(folio_list);
+       struct folio *folio;
 
        addr = r->ar.start;
        while (addr < r->ar.end) {
-               struct folio *folio = damon_get_folio(PHYS_PFN(addr));
-
-               if (!folio) {
+               folio = damon_get_folio(PHYS_PFN(addr));
+               if (damon_pa_invalid_damos_folio(folio, s)) {
                        addr += PAGE_SIZE;
                        continue;
                }
@@ -506,6 +519,7 @@ put_folio:
        }
        applied = damon_pa_migrate_pages(&folio_list, s->target_nid);
        cond_resched();
+       s->last_applied = folio;
        return applied * PAGE_SIZE;
 }
 
@@ -523,15 +537,15 @@ static unsigned long damon_pa_stat(struct damon_region *r, struct damos *s,
 {
        unsigned long addr;
        LIST_HEAD(folio_list);
+       struct folio *folio;
 
        if (!damon_pa_scheme_has_filter(s))
                return 0;
 
        addr = r->ar.start;
        while (addr < r->ar.end) {
-               struct folio *folio = damon_get_folio(PHYS_PFN(addr));
-
-               if (!folio) {
+               folio = damon_get_folio(PHYS_PFN(addr));
+               if (damon_pa_invalid_damos_folio(folio, s)) {
                        addr += PAGE_SIZE;
                        continue;
                }
@@ -541,6 +555,7 @@ static unsigned long damon_pa_stat(struct damon_region *r, struct damos *s,
                addr += folio_size(folio);
                folio_put(folio);
        }
+       s->last_applied = folio;
        return 0;
 }