FAILED: patch "[PATCH] mm, swap: speed up hibernation allocation and writeout" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] mm, swap: speed up hibernation allocation and writeout" failed to apply to 6.18-stable tree

[gregkh]

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 396f57b5720024638dbb503f6a4abd988a49d815
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026050440-judgingly-glandular-5a54@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 396f57b5720024638dbb503f6a4abd988a49d815 Mon Sep 17 00:00:00 2001
From: Kairui Song <kasong@tencent.com>
Date: Mon, 16 Feb 2026 22:58:02 +0800
Subject: [PATCH] mm, swap: speed up hibernation allocation and writeout

Since commit 0ff67f990bd4 ("mm, swap: remove swap slot cache"),
hibernation has been using the swap slot slow allocation path for
simplification, which turns out might cause regression for some devices
because the allocator now rotates clusters too often, leading to slower
allocation and more random distribution of data.

Fast allocation is not complex, so implement hibernation support as well.

Test result with Samsung SSD 830 Series (SATA II, 3.0 Gbps) shows the
performance is several times better [1]:
6.19:               324 seconds
After this series:  35 seconds

Link: https://lkml.kernel.org/r/20260216-hibernate-perf-v4-1-1ba9f0bf1ec9@tencent.com
Link: https://lore.kernel.org/linux-mm/8b4bdcfa-ce3f-4e23-839f-31367df7c18f@gmx.de/ [1]
Signed-off-by: Kairui Song <kasong@tencent.com>
Fixes: 0ff67f990bd4 ("mm, swap: remove swap slot cache")
Reported-by: Carsten Grohmann <mail@carstengrohmann.de>
Closes: https://lore.kernel.org/linux-mm/20260206121151.dea3633d1f0ded7bbf49c22e@linux-foundation.org/
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 94af29d1de88..90132b74d6a0 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1926,8 +1926,9 @@ void swap_put_entries_direct(swp_entry_t entry, int nr)
 /* Allocate a slot for hibernation */
 swp_entry_t swap_alloc_hibernation_slot(int type)
 {
-	struct swap_info_struct *si = swap_type_to_info(type);
-	unsigned long offset;
+	struct swap_info_struct *pcp_si, *si = swap_type_to_info(type);
+	unsigned long pcp_offset, offset = SWAP_ENTRY_INVALID;
+	struct swap_cluster_info *ci;
 	swp_entry_t entry = {0};
 
 	if (!si)
@@ -1937,11 +1938,21 @@ swp_entry_t swap_alloc_hibernation_slot(int type)
 	if (get_swap_device_info(si)) {
 		if (si->flags & SWP_WRITEOK) {
 			/*
-			 * Grab the local lock to be compliant
-			 * with swap table allocation.
+			 * Try the local cluster first if it matches the device. If
+			 * not, try grab a new cluster and override local cluster.
 			 */
 			local_lock(&percpu_swap_cluster.lock);
-			offset = cluster_alloc_swap_entry(si, NULL);
+			pcp_si = this_cpu_read(percpu_swap_cluster.si[0]);
+			pcp_offset = this_cpu_read(percpu_swap_cluster.offset[0]);
+			if (pcp_si == si && pcp_offset) {
+				ci = swap_cluster_lock(si, pcp_offset);
+				if (cluster_is_usable(ci, 0))
+					offset = alloc_swap_scan_cluster(si, ci, NULL, pcp_offset);
+				else
+					swap_cluster_unlock(ci);
+			}
+			if (!offset)
+				offset = cluster_alloc_swap_entry(si, NULL);
 			local_unlock(&percpu_swap_cluster.lock);
 			if (offset)
 				entry = swp_entry(si->type, offset);