linux-kernel - [RFC PATCH v2 03/18] swapfile: rearrange freeing steps

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Message-ID: <20250429233848.3093350-4-nphamcs@gmail.com>
Date: Tue, 29 Apr 2025 16:38:31 -0700
From: Nhat Pham <nphamcs@...il.com>
To: linux-mm@...ck.org
Cc: akpm@...ux-foundation.org,
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Subject: [RFC PATCH v2 03/18] swapfile: rearrange freeing steps

In the swap free path, certain steps (cgroup uncharging and shadow
clearing) will be handled at the virtual layer eventually. To facilitate
this change, rearrange these functions a bit in their caller. There
should not be any functional change.

Signed-off-by: Nhat Pham <nphamcs@...il.com>
---
 mm/swapfile.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 426674d35983..e717d0e7ae6b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1129,6 +1129,8 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
 	void (*swap_slot_free_notify)(struct block_device *, unsigned long);
 	unsigned int i;
 
+	clear_shadow_from_swap_cache(si->type, begin, end);
+
 	/*
 	 * Use atomic clear_bit operations only on zeromap instead of non-atomic
 	 * bitmap_clear to prevent adjacent bits corruption due to simultaneous writes.
@@ -1149,7 +1151,6 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
 			swap_slot_free_notify(si->bdev, offset);
 		offset++;
 	}
-	clear_shadow_from_swap_cache(si->type, begin, end);
 
 	/*
 	 * Make sure that try_to_unuse() observes si->inuse_pages reaching 0
@@ -1502,6 +1503,8 @@ static void swap_entry_range_free(struct swap_info_struct *si,
 	unsigned char *map = si->swap_map + offset;
 	unsigned char *map_end = map + nr_pages;
 
+	mem_cgroup_uncharge_swap(entry, nr_pages);
+
 	/* It should never free entries across different clusters */
 	VM_BUG_ON(ci != offset_to_cluster(si, offset + nr_pages - 1));
 	VM_BUG_ON(cluster_is_empty(ci));
@@ -1513,7 +1516,6 @@ static void swap_entry_range_free(struct swap_info_struct *si,
 		*map = 0;
 	} while (++map < map_end);
 
-	mem_cgroup_uncharge_swap(entry, nr_pages);
 	swap_range_free(si, offset, nr_pages);
 
 	if (!ci->count)
-- 
2.47.1