From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta0.migadu.com (out-177.mta0.migadu.com [91.218.175.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 443E92DEA7B for ; Fri, 15 May 2026 01:57:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778810277; cv=none; b=LXzxH+sm4JJboHfMayqT1An+bkTJ/KQIuBulTrCIEXzKTDgl9fCn/gPOFqhiaj2cYFkTPcSIO3XTshf/cIENGAHziVBOmLn2XlINMYu5bdfsyjiL0cpV1l33wzp1DKFJOjgD42yU+dunL5/ksTRDJBl0lfhXtGP2Yusk+TS/Ws4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778810277; c=relaxed/simple; bh=7AvDrNyupV4/wMIJNhNUfuHKlNSILUUPu2lPvIsLAl4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-type; b=bwCFIU5Fe/sMUfyydmQyc5Cq4D/F6LVh3OW+1na8td0V+uLCmPRPi3hqbs3ump5wiVyhOUPJRe7wAj+N0x//GHAw8K5TiDBkAn7/LwBas8vFrR78BX+FLJXYvYT4PZBzA9w8k98NhJxjHPyijnOP+9CCEmv9Ut6wXUhU00Os1U8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=xw9e8+1v; arc=none smtp.client-ip=91.218.175.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="xw9e8+1v" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1778810273; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wEsHsxQav2TvnbIZZsTRBwS8toLmw21bJKCaqNlP5NQ=; b=xw9e8+1vwCgkcaae38RYCgz4aaH0mPkRcN82TT0yXf7CDFlxh69Of5vRpac4PmZ6qCQUZF L4ioAws5aTUT9J81QAwJvFpyuIammi0RsbYVBHFxARl9yWbBVEW7Db8YUV3nzpg99KndVg UDFUy7uw0x3uNmHLFVIZy9jLiGwFXaE= From: Baoquan He To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, chrisl@kernel.org, usama.arif@linux.dev, baohua@kernel.org, kasong@tencent.com, nphamcs@gmail.com, shikemeng@huaweicloud.com, youngjun.park@lge.com, hch@infradead.org, linux-kernel@vger.kernel.org, Baoquan He Subject: [PATCH v7 1/3] mm/swap: use swap_ops to register swap device's methods Date: Fri, 15 May 2026 09:57:35 +0800 Message-ID: <20260515015737.890994-2-baoquan.he@linux.dev> In-Reply-To: <20260515015737.890994-1-baoquan.he@linux.dev> References: <20260515015737.890994-1-baoquan.he@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-type: text/plain Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT This simplifies codes and makes logic clearer. And also makes later any new swap device type being added easier to handle. Currently there are three types of swap devices: bdev_fs, bdev_sync and bdev_async, and only operations read_folio and write_folio are included. In the future, there could be more swap device types added and more appropriate operations adapted into swap_ops. Suggested-by: Chris Li Signed-off-by: Baoquan He --- include/linux/swap.h | 3 ++ mm/page_io.c | 104 +++++++++++++++++++++++++------------------ mm/swap.h | 10 ++++- mm/swapfile.c | 9 ++++ mm/zswap.c | 2 +- 5 files changed, 83 insertions(+), 45 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 7a09df6977a5..0d045fc8ec35 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -20,6 +20,8 @@ struct notifier_block; struct bio; +struct swap_ops; + #define SWAP_FLAG_PREFER 0x8000 /* set if swap priority specified */ #define SWAP_FLAG_PRIO_MASK 0x7fff #define SWAP_FLAG_DISCARD 0x10000 /* enable discard for swap */ @@ -282,6 +284,7 @@ struct swap_info_struct { struct work_struct reclaim_work; /* reclaim worker */ struct list_head discard_clusters; /* discard clusters list */ struct plist_node avail_list; /* entry in swap_avail_head */ + const struct swap_ops *ops; }; static inline swp_entry_t page_swap_entry(struct page *page) diff --git a/mm/page_io.c b/mm/page_io.c index 70cea9e24d2f..2b520af88376 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -240,6 +240,9 @@ static void swap_zeromap_folio_clear(struct folio *folio) int swap_writeout(struct folio *folio, struct swap_iocb **swap_plug) { int ret = 0; + struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); + + VM_WARN_ON_FOLIO(!folio_test_swapcache(folio), folio); if (folio_free_swap(folio)) goto out_unlock; @@ -285,7 +288,7 @@ int swap_writeout(struct folio *folio, struct swap_iocb **swap_plug) } rcu_read_unlock(); - __swap_writepage(folio, swap_plug); + sis->ops->write_folio(sis, folio, swap_plug); return 0; out_unlock: folio_unlock(folio); @@ -375,10 +378,11 @@ static void sio_write_complete(struct kiocb *iocb, long ret) mempool_free(sio, sio_pool); } -static void swap_writepage_fs(struct folio *folio, struct swap_iocb **swap_plug) +static void swap_writepage_fs(struct swap_info_struct *sis, + struct folio *folio, + struct swap_iocb **swap_plug) { struct swap_iocb *sio = swap_plug ? *swap_plug : NULL; - struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); struct file *swap_file = sis->swap_file; loff_t pos = swap_dev_pos(folio->swap); @@ -411,8 +415,9 @@ static void swap_writepage_fs(struct folio *folio, struct swap_iocb **swap_plug) *swap_plug = sio; } -static void swap_writepage_bdev_sync(struct folio *folio, - struct swap_info_struct *sis) +static void swap_writepage_bdev_sync(struct swap_info_struct *sis, + struct folio *folio, + struct swap_iocb **plug) { struct bio_vec bv; struct bio bio; @@ -431,8 +436,9 @@ static void swap_writepage_bdev_sync(struct folio *folio, __end_swap_bio_write(&bio); } -static void swap_writepage_bdev_async(struct folio *folio, - struct swap_info_struct *sis) +static void swap_writepage_bdev_async(struct swap_info_struct *sis, + struct folio *folio, + struct swap_iocb **plug) { struct bio *bio; @@ -448,29 +454,6 @@ static void swap_writepage_bdev_async(struct folio *folio, submit_bio(bio); } -void __swap_writepage(struct folio *folio, struct swap_iocb **swap_plug) -{ - struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); - - VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio); - /* - * ->flags can be updated non-atomically, - * but that will never affect SWP_FS_OPS, so the data_race - * is safe. - */ - if (data_race(sis->flags & SWP_FS_OPS)) - swap_writepage_fs(folio, swap_plug); - /* - * ->flags can be updated non-atomically, - * but that will never affect SWP_SYNCHRONOUS_IO, so the data_race - * is safe. - */ - else if (data_race(sis->flags & SWP_SYNCHRONOUS_IO)) - swap_writepage_bdev_sync(folio, sis); - else - swap_writepage_bdev_async(folio, sis); -} - void swap_write_unplug(struct swap_iocb *sio) { struct iov_iter from; @@ -539,9 +522,10 @@ static bool swap_read_folio_zeromap(struct folio *folio) return true; } -static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug) +static void swap_read_folio_fs(struct swap_info_struct *sis, + struct folio *folio, + struct swap_iocb **plug) { - struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); struct swap_iocb *sio = NULL; loff_t pos = swap_dev_pos(folio->swap); @@ -573,8 +557,9 @@ static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug) *plug = sio; } -static void swap_read_folio_bdev_sync(struct folio *folio, - struct swap_info_struct *sis) +static void swap_read_folio_bdev_sync(struct swap_info_struct *sis, + struct folio *folio, + struct swap_iocb **plug) { struct bio_vec bv; struct bio bio; @@ -595,8 +580,9 @@ static void swap_read_folio_bdev_sync(struct folio *folio, put_task_struct(current); } -static void swap_read_folio_bdev_async(struct folio *folio, - struct swap_info_struct *sis) +static void swap_read_folio_bdev_async(struct swap_info_struct *sis, + struct folio *folio, + struct swap_iocb **plug) { struct bio *bio; @@ -610,6 +596,44 @@ static void swap_read_folio_bdev_async(struct folio *folio, submit_bio(bio); } +static const struct swap_ops bdev_fs_swap_ops = { + .read_folio = swap_read_folio_fs, + .write_folio = swap_writepage_fs, +}; + +static const struct swap_ops bdev_sync_swap_ops = { + .read_folio = swap_read_folio_bdev_sync, + .write_folio = swap_writepage_bdev_sync, +}; + +static const struct swap_ops bdev_async_swap_ops = { + .read_folio = swap_read_folio_bdev_async, + .write_folio = swap_writepage_bdev_async, +}; + +int init_swap_ops(struct swap_info_struct *sis) +{ + /* + * ->flags can be updated non-atomically, but that will + * never affect SWP_FS_OPS, so the data_race is safe. + */ + if (data_race(sis->flags & SWP_FS_OPS)) + sis->ops = &bdev_fs_swap_ops; + /* + * ->flags can be updated non-atomically, but that will + * never affect SWP_SYNCHRONOUS_IO, so the data_race is safe. + */ + else if (data_race(sis->flags & SWP_SYNCHRONOUS_IO)) + sis->ops = &bdev_sync_swap_ops; + else + sis->ops = &bdev_async_swap_ops; + + if (!sis->ops || !sis->ops->read_folio || !sis->ops->write_folio) + return -EINVAL; + + return 0; +} + void swap_read_folio(struct folio *folio, struct swap_iocb **plug) { struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); @@ -644,13 +668,7 @@ void swap_read_folio(struct folio *folio, struct swap_iocb **plug) /* We have to read from slower devices. Increase zswap protection. */ zswap_folio_swapin(folio); - if (data_race(sis->flags & SWP_FS_OPS)) { - swap_read_folio_fs(folio, plug); - } else if (synchronous) { - swap_read_folio_bdev_sync(folio, sis); - } else { - swap_read_folio_bdev_async(folio, sis); - } + sis->ops->read_folio(sis, folio, plug); finish: if (workingset) { diff --git a/mm/swap.h b/mm/swap.h index a77016f2423b..8d4375f91632 100644 --- a/mm/swap.h +++ b/mm/swap.h @@ -217,6 +217,15 @@ extern void __swap_cluster_free_entries(struct swap_info_struct *si, /* linux/mm/page_io.c */ int sio_pool_init(void); struct swap_iocb; +struct swap_ops { + void (*read_folio)(struct swap_info_struct *sis, + struct folio *folio, + struct swap_iocb **plug); + void (*write_folio)(struct swap_info_struct *sis, + struct folio *folio, + struct swap_iocb **plug); +}; +int init_swap_ops(struct swap_info_struct *sis); void swap_read_folio(struct folio *folio, struct swap_iocb **plug); void __swap_read_unplug(struct swap_iocb *plug); static inline void swap_read_unplug(struct swap_iocb *plug) @@ -226,7 +235,6 @@ static inline void swap_read_unplug(struct swap_iocb *plug) } void swap_write_unplug(struct swap_iocb *sio); int swap_writeout(struct folio *folio, struct swap_iocb **swap_plug); -void __swap_writepage(struct folio *folio, struct swap_iocb **swap_plug); /* linux/mm/swap_state.c */ extern struct address_space swap_space __read_mostly; diff --git a/mm/swapfile.c b/mm/swapfile.c index 9174f1eeffb0..29ae79d0fa2e 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -3597,6 +3597,15 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) } } + /* + * init_swap_ops() sets si->ops based on flags. It does not need + * swapon_mutex, and must complete before enable_swap_info() + * exposes the device. + */ + error = init_swap_ops(si); + if (error) + goto bad_swap_unlock_inode; + error = zswap_swapon(si->type, maxpages); if (error) goto bad_swap_unlock_inode; diff --git a/mm/zswap.c b/mm/zswap.c index 4b5149173b0e..192401f46de4 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1054,7 +1054,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry, folio_set_reclaim(folio); /* start writeback */ - __swap_writepage(folio, NULL); + si->ops->write_folio(si, folio, NULL); out: if (ret && ret != -EEXIST) { -- 2.52.0