linux-kernel - [PATCH v2 1/2] mm/damon: add a min_sz_region parameter to damon_set_region_biggest_system_ram

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Message-ID: <20251020130125.2875164-2-yanquanmin1@huawei.com>
Date: Mon, 20 Oct 2025 21:01:24 +0800
From: Quanmin Yan <yanquanmin1@...wei.com>
To: <sj@...nel.org>
CC: <akpm@...ux-foundation.org>, <damon@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<yanquanmin1@...wei.com>, <wangkefeng.wang@...wei.com>, <zuoze1@...wei.com>
Subject: [PATCH v2 1/2] mm/damon: add a min_sz_region parameter to damon_set_region_biggest_system_ram_default()

In DAMON_LRU_SORT, damon_set_regions() will apply DAMON_MIN_REGION as
the core address alignment, and the monitoring target address ranges
would be aligned on DAMON_MIN_REGION * addr_unit. When users 1) set
addr_unit to a value larger than 1, and 2) set the monitoring target
address range as not aligned on DAMON_MIN_REGION * addr_unit, it will
cause DAMON_LRU_SORT to operate on unexpectedly large physical address
ranges.

For example, if the user sets the monitoring target address range to
[4, 8) and addr_unit as 1024, the aimed monitoring target address range
is [4 KiB, 8 KiB). Assuming DAMON_MIN_REGION is 4096, so resulting
target address range will be [0, 4096) in the DAMON core layer address
system, and [0, 4 MiB) in the physical address space, which is an
unexpected range.

To fix the issue, add a min_sz_region parameter to
damon_set_region_biggest_system_ram_default() and use it when calling
damon_set_regions(), replacing the direct use of DAMON_MIN_REGION.

Fixes: 2e0fe9245d6b ("mm/damon/lru_sort: support addr_unit for DAMON_LRU_SORT")
Signed-off-by: Quanmin Yan <yanquanmin1@...wei.com>
---
 include/linux/damon.h | 3 ++-
 mm/damon/core.c       | 6 ++++--
 mm/damon/lru_sort.c   | 3 ++-
 mm/damon/reclaim.c    | 3 ++-
 mm/damon/stat.c       | 3 ++-
 5 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index cae8c613c5fc..1ce75a20febf 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -947,7 +947,8 @@ int damon_call(struct damon_ctx *ctx, struct damon_call_control *control);
 int damos_walk(struct damon_ctx *ctx, struct damos_walk_control *control);
 
 int damon_set_region_biggest_system_ram_default(struct damon_target *t,
-				unsigned long *start, unsigned long *end);
+				unsigned long *start, unsigned long *end,
+				unsigned long min_sz_region);
 
 #endif	/* CONFIG_DAMON */
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 109b050c795a..dbe48e43682b 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -2770,6 +2770,7 @@ static bool damon_find_biggest_system_ram(unsigned long *start,
  * @t:		The monitoring target to set the region.
  * @start:	The pointer to the start address of the region.
  * @end:	The pointer to the end address of the region.
+ * @min_sz_region:	Minimum region size.
  *
  * This function sets the region of @t as requested by @start and @end.  If the
  * values of @start and @end are zero, however, this function finds the biggest
@@ -2780,7 +2781,8 @@ static bool damon_find_biggest_system_ram(unsigned long *start,
  * Return: 0 on success, negative error code otherwise.
  */
 int damon_set_region_biggest_system_ram_default(struct damon_target *t,
-			unsigned long *start, unsigned long *end)
+			unsigned long *start, unsigned long *end,
+			unsigned long min_sz_region)
 {
 	struct damon_addr_range addr_range;
 
@@ -2793,7 +2795,7 @@ int damon_set_region_biggest_system_ram_default(struct damon_target *t,
 
 	addr_range.start = *start;
 	addr_range.end = *end;
-	return damon_set_regions(t, &addr_range, 1, DAMON_MIN_REGION);
+	return damon_set_regions(t, &addr_range, 1, min_sz_region);
 }
 
 /*
diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
index 42b9a656f9de..49b4bc294f4e 100644
--- a/mm/damon/lru_sort.c
+++ b/mm/damon/lru_sort.c
@@ -242,7 +242,8 @@ static int damon_lru_sort_apply_parameters(void)
 
 	err = damon_set_region_biggest_system_ram_default(param_target,
 					&monitor_region_start,
-					&monitor_region_end);
+					&monitor_region_end,
+					param_ctx->min_sz_region);
 	if (err)
 		goto out;
 	err = damon_commit_ctx(ctx, param_ctx);
diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index 7ba3d0f9a19a..e30811cafe90 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -250,7 +250,8 @@ static int damon_reclaim_apply_parameters(void)
 
 	err = damon_set_region_biggest_system_ram_default(param_target,
 					&monitor_region_start,
-					&monitor_region_end);
+					&monitor_region_end,
+					DAMON_MIN_REGION);
 	if (err)
 		goto out;
 	err = damon_commit_ctx(ctx, param_ctx);
diff --git a/mm/damon/stat.c b/mm/damon/stat.c
index d8010968bbed..6c4503d2aee3 100644
--- a/mm/damon/stat.c
+++ b/mm/damon/stat.c
@@ -187,7 +187,8 @@ static struct damon_ctx *damon_stat_build_ctx(void)
 	if (!target)
 		goto free_out;
 	damon_add_target(ctx, target);
-	if (damon_set_region_biggest_system_ram_default(target, &start, &end))
+	if (damon_set_region_biggest_system_ram_default(target, &start, &end,
+							ctx->min_sz_region))
 		goto free_out;
 	return ctx;
 free_out:
-- 
2.43.0