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Wed, 18 Mar 2026 15:30:06 -0700 (PDT) Received: from localhost ([2a03:2880:10ff:73::]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-41bd22dee78sm4108849fac.0.2026.03.18.15.30.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 15:30:06 -0700 (PDT) From: Nhat Pham To: kasong@tencent.com Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org, apopple@nvidia.com, axelrasmussen@google.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, bhe@redhat.com, byungchul@sk.com, cgroups@vger.kernel.org, chengming.zhou@linux.dev, chrisl@kernel.org, corbet@lwn.net, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jannh@google.com, joshua.hahnjy@gmail.com, lance.yang@linux.dev, lenb@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org, lorenzo.stoakes@oracle.com, matthew.brost@intel.com, mhocko@suse.com, muchun.song@linux.dev, npache@redhat.com, nphamcs@gmail.com, pavel@kernel.org, peterx@redhat.com, peterz@infradead.org, pfalcato@suse.de, rafael@kernel.org, rakie.kim@sk.com, roman.gushchin@linux.dev, rppt@kernel.org, ryan.roberts@arm.com, shakeel.butt@linux.dev, shikemeng@huaweicloud.com, surenb@google.com, tglx@kernel.org, vbabka@suse.cz, weixugc@google.com, ying.huang@linux.alibaba.com, yosry.ahmed@linux.dev, yuanchu@google.com, zhengqi.arch@bytedance.com, ziy@nvidia.com, kernel-team@meta.com, riel@surriel.com Subject: [PATCH v4 07/21] mm: create scaffolds for the new virtual swap implementation Date: Wed, 18 Mar 2026 15:29:38 -0700 Message-ID: <20260318222953.441758-8-nphamcs@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260318222953.441758-1-nphamcs@gmail.com> References: <20260318222953.441758-1-nphamcs@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 31D094000B X-Stat-Signature: cyibbcszbpm7yn3mwix83bhxqcexqryo X-Rspam-User: X-HE-Tag: 1773873007-188292 X-HE-Meta: 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 RtBBhTq/ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: In prepration for the implementation of swap virtualization, add new scaffolds for the new code: a new mm/vswap.c source file, which currently only holds the logic to set up the (for now, empty) vswap debugfs directory. Hook this up in the swap setup step in mm/swap_state.c, and set up vswap compilation in the Makefile. Other than the debugfs directory, no behavioral change intended. Finally, make Johannes a swap reviewer, given that he has contributed majorly to the developments of virtual swap. Signed-off-by: Nhat Pham --- MAINTAINERS | 2 ++ include/linux/swap.h | 3 +++ mm/Makefile | 2 +- mm/swap_state.c | 6 ++++++ mm/vswap.c | 35 +++++++++++++++++++++++++++++++++++ 5 files changed, 47 insertions(+), 1 deletion(-) create mode 100644 mm/vswap.c diff --git a/MAINTAINERS b/MAINTAINERS index e087673237636..b21038b160a07 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -16728,6 +16728,7 @@ R: Kemeng Shi R: Nhat Pham R: Baoquan He R: Barry Song +R: Johannes Weiner L: linux-mm@kvack.org S: Maintained F: Documentation/mm/swap-table.rst @@ -16740,6 +16741,7 @@ F: mm/swap.h F: mm/swap_table.h F: mm/swap_state.c F: mm/swapfile.c +F: mm/vswap.c MEMORY MANAGEMENT - THP (TRANSPARENT HUGE PAGE) M: Andrew Morton diff --git a/include/linux/swap.h b/include/linux/swap.h index 918b47da55f44..df0771903a952 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -423,6 +423,9 @@ extern void __meminit kswapd_stop(int nid); #ifdef CONFIG_SWAP +/* Virtual swap space API (mm/vswap.c) */ +int vswap_init(void); + /* Lifecycle swap API (mm/swapfile.c) */ int folio_alloc_swap(struct folio *folio); bool folio_free_swap(struct folio *folio); diff --git a/mm/Makefile b/mm/Makefile index 2d0570a16e5be..67fa4586e7e18 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -75,7 +75,7 @@ ifdef CONFIG_MMU obj-$(CONFIG_ADVISE_SYSCALLS) += madvise.o endif -obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o +obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o vswap.o obj-$(CONFIG_ZSWAP) += zswap.o obj-$(CONFIG_HAS_DMA) += dmapool.o obj-$(CONFIG_HUGETLBFS) += hugetlb.o hugetlb_sysfs.o hugetlb_sysctl.o diff --git a/mm/swap_state.c b/mm/swap_state.c index e2e9f55bea3bb..29ec666be4204 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -882,6 +882,12 @@ static int __init swap_init(void) int err; struct kobject *swap_kobj; + err = vswap_init(); + if (err) { + pr_err("failed to initialize virtual swap space\n"); + return err; + } + swap_kobj = kobject_create_and_add("swap", mm_kobj); if (!swap_kobj) { pr_err("failed to create swap kobject\n"); diff --git a/mm/vswap.c b/mm/vswap.c new file mode 100644 index 0000000000000..e68234f053fc9 --- /dev/null +++ b/mm/vswap.c @@ -0,0 +1,35 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Virtual swap space + * + * Copyright (C) 2024 Meta Platforms, Inc., Nhat Pham + */ +#include + +#ifdef CONFIG_DEBUG_FS +#include + +static struct dentry *vswap_debugfs_root; + +static int vswap_debug_fs_init(void) +{ + if (!debugfs_initialized()) + return -ENODEV; + + vswap_debugfs_root = debugfs_create_dir("vswap", NULL); + return 0; +} +#else +static int vswap_debug_fs_init(void) +{ + return 0; +} +#endif + +int vswap_init(void) +{ + if (vswap_debug_fs_init()) + pr_warn("Failed to initialize vswap debugfs\n"); + + return 0; +} -- 2.52.0