linux-kernel - [PATCH v2 3/9] mm/swap: avoid doing extra unlock error checks for direct swapin

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Date: Wed,  3 Jan 2024 01:53:32 +0800
From: Kairui Song <ryncsn@...il.com>
To: linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Chris Li <chrisl@...nel.org>,
	"Huang, Ying" <ying.huang@...el.com>,
	Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Matthew Wilcox <willy@...radead.org>,
	Michal Hocko <mhocko@...e.com>,
	Yosry Ahmed <yosryahmed@...gle.com>,
	David Hildenbrand <david@...hat.com>,
	linux-kernel@...r.kernel.org,
	Kairui Song <kasong@...cent.com>
Subject: [PATCH v2 3/9] mm/swap: avoid doing extra unlock error checks for direct swapin

From: Kairui Song <kasong@...cent.com>

When swapping in a page, mem_cgroup_swapin_charge_folio is called for
new allocated folio, nothing else is referencing the folio so no need
to set the lock bit early. This avoided doing extra unlock checks
on the error path.

Signed-off-by: Kairui Song <kasong@...cent.com>
---
 mm/swap_state.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 24cb93ed5081..6130de8d5226 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -881,16 +881,15 @@ struct folio *swapin_direct(swp_entry_t entry, gfp_t gfp_mask,
 	folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0,
 				vma, vmf->address, false);
 	if (folio) {
-		__folio_set_locked(folio);
-		__folio_set_swapbacked(folio);
-
-		if (mem_cgroup_swapin_charge_folio(folio,
-					vma->vm_mm, GFP_KERNEL,
-					entry)) {
-			folio_unlock(folio);
+		if (mem_cgroup_swapin_charge_folio(folio, vma->vm_mm,
+						   GFP_KERNEL, entry)) {
 			folio_put(folio);
 			return NULL;
 		}
+
+		__folio_set_locked(folio);
+		__folio_set_swapbacked(folio);
+
 		mem_cgroup_swapin_uncharge_swap(entry);
 
 		shadow = get_shadow_from_swap_cache(entry);
-- 
2.43.0