From: Baoquan He <baoquan.he@linux.dev>
To: linux-mm@kvack.org
Cc: akpm@linux-foundation.org, david@kernel.org, chrisl@kernel.org,
kasong@tencent.com, nphamcs@gmail.com, baohua@kernel.org,
youngjun.park@lge.com, corbet@lwn.net, hannes@cmpxchg.org,
chengming.zhou@linux.dev, kunwu.chan@gmail.com,
klarasmodin@gmail.com, linux-kernel@vger.kernel.org,
Baoquan He <hebaoquan@kylinos.cn>
Subject: [PATCH v5 08/19] mm, swap: require zswap for xswap devices
Date: Mon, 9 Nov 2026 13:54:44 +0800 [thread overview]
Message-ID: <20261109055455.536925-9-baoquan.he@linux.dev> (raw)
In-Reply-To: <20261109055455.536925-1-baoquan.he@linux.dev>
From: Baoquan He <hebaoquan@kylinos.cn>
xswap pages live only in zswap. Without zswap, swapout cannot
free the page, but still takes a swap entry. So the device consumes
swap entries without freeing memory. Fail to create a device when
zswap is unavailable.
Acked-by: Chris Li <chrisl@kernel.org>
Signed-off-by: Baoquan He <hebaoquan@kylinos.cn>
---
mm/swapfile.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 3f2b863f7dd7..35c8aac1e25d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -4268,6 +4268,10 @@ static int xswap_create(int prio)
(prio < 0 || prio > SWAP_FLAG_PRIO_MASK))
return -EINVAL;
+ /* xswap has no backing store, it relies on zswap. */
+ if (!zswap_is_enabled())
+ return -EOPNOTSUPP;
+
si = alloc_swap_info();
if (IS_ERR(si))
return PTR_ERR(si);
--
2.54.0
next prev parent reply other threads:[~2026-11-09 5:56 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-09 5:54 [PATCH v5 00/19] mm, swap: extendable swap devices (xswap phase I) Baoquan He
2026-11-09 5:54 ` [PATCH v5 01/19] mm: xswap support for zswap Baoquan He
2026-11-09 5:54 ` [PATCH v5 02/19] mm, swap: refactor free_swap_cluster_info to take swap_info_struct Baoquan He
2026-11-09 5:54 ` [PATCH v5 03/19] mm, swap: add VM_SPARSE cluster-array helpers for xswap Baoquan He
2026-11-09 5:54 ` [PATCH v5 04/19] mm, swap: use a VM_SPARSE cluster array for xswap devices Baoquan He
2026-11-09 5:54 ` [PATCH v5 05/19] mm, swap: widen swap_info_struct max/pages to unsigned long Baoquan He
2026-11-09 5:54 ` [PATCH v5 06/19] mm, swap: add a sysfs interface to create xswap devices Baoquan He
2026-11-09 5:54 ` [PATCH v5 07/19] mm, swap: refactor swapoff and add xswap_destroy Baoquan He
2026-11-09 5:54 ` Baoquan He [this message]
2026-11-09 5:54 ` [PATCH v5 09/19] mm, swap: use a stable id for xswap devices Baoquan He
2026-11-09 5:54 ` [PATCH v5 10/19] mm, swap: let the command line set the xswap device size Baoquan He
2026-11-09 5:54 ` [PATCH v5 11/19] mm, swap: add CONFIG_XSWAP_DEFAULT_MAX Baoquan He
2026-11-09 5:54 ` [PATCH v5 12/19] mm, swap: let swapoff destroy xswap devices by name Baoquan He
2026-11-09 5:54 ` [PATCH v5 13/19] mm, swap: add xswap grow trigger on cluster allocation Baoquan He
2026-11-09 5:54 ` [PATCH v5 14/19] mm, swap: add debugfs counters for xswap Baoquan He
2026-11-09 5:54 ` [PATCH v5 15/19] mm, swap: make xswap cluster_info accesses RCU-safe Baoquan He
2026-11-09 5:54 ` [PATCH v5 16/19] mm, swap: prepare xswap_unmap_clusters for range shrinking Baoquan He
2026-11-09 5:54 ` [PATCH v5 17/19] mm, swap: add xswap shrink trigger and defer it to a workqueue Baoquan He
2026-11-09 5:54 ` [PATCH v5 18/19] mm, swap: do not give an xswap slot to a cgroup that cannot zswap Baoquan He
2026-11-09 5:54 ` [PATCH v5 19/19] mm, swap: skip the overcommit probe when removing xswap Baoquan He
2026-11-09 6:15 ` [PATCH v5 00/19] mm, swap: extendable swap devices (xswap phase I) Baoquan He
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