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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1776243441; 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=hS5qpEiCkYhxSwO473MIhVovQuf7CZrjA9Nb/Pirvks=; b=KsL0a7bC9pDxfCYS0pbMhEeCJ3V6Z4KmdX93mIJ4/P3N4/MA/we2Nm/qapyNOrPSY8UUuz 3QWCwZXwwB+CRKYKIgoYPWZCZ36T+vBk4qkYJwrSOmmTQYAw9PFUByeFGVosaBjYhLUeDK y2VmiVxwWKOc/yTQ1EZJwFuowO32vPg= From: Baoquan He To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, baohua@kernel.org, chrisl@kernel.org, kasong@tencent.com, nphamcs@gmail.com, shikemeng@huaweicloud.com, youngjun.park@lge.com, linux-kernel@vger.kernel.org, Baoquan He Subject: [PATCH v3 2/3] mm/swap: use swap_ops to register swap device's methods Date: Wed, 15 Apr 2026 16:56:57 +0800 Message-ID: <20260415085658.993859-3-baoquan.he@linux.dev> In-Reply-To: <20260415085658.993859-1-baoquan.he@linux.dev> References: <20260415085658.993859-1-baoquan.he@linux.dev> MIME-Version: 1.0 Content-type: text/plain Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: F0E6180008 X-Stat-Signature: 1s1kkbgn6gmf6nj39x84yjhpxsq5c8sx X-HE-Tag: 1776243443-605350 X-HE-Meta: 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 vrWq0icn JeijTSwFXIfDTiWbC5PyqyUcixg5M9z5qS1a0bB+IXTtA2yNBsrbvqZuJMExxAENlEh4jyR3ZlxIYv7Tv6eFrFnuHmw6+/50EkiqCLTklS0rsZqC93qwomeNIVF+eII0PIZ1BwZOosLpC9Zkl4a+RDqf0vPeJ8X9mGTIQXh+ET33hMNgE0LXn2Nsf40/lRxYGuPJiHmZ3gwBUI/Cam2v73nsGS8cs+w/vw/u8ptFlYZSyLw1mMEjY27HGsZdS0SjZfIPMWt7nbKNOGbWVHVfrA8GIkQm0Rz7hn/cMiYrdT/METb4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 opeations adapted into swap_ops. Suggested-by: Chris Li Co-developed-by: Barry Song Signed-off-by: Barry Song Signed-off-by: Baoquan He --- include/linux/swap.h | 2 + mm/swap.h | 10 ++++- mm/swap_io.c | 102 +++++++++++++++++++++++++------------------ mm/swapfile.c | 5 +++ mm/zswap.c | 2 +- 5 files changed, 76 insertions(+), 45 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 62fc7499b408..3069bbfd7a05 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -255,6 +255,7 @@ struct swap_sequential_cluster { unsigned int next[SWAP_NR_ORDERS]; /* Likely next allocation offset */ }; +struct swap_ops; /* * The in-memory structure used to track swap areas. */ @@ -300,6 +301,7 @@ 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/swap.h b/mm/swap.h index 81a80605fc6a..0f4c597e3f28 100644 --- a/mm/swap.h +++ b/mm/swap.h @@ -213,6 +213,15 @@ extern void swap_entries_free(struct swap_info_struct *si, /* linux/mm/swap_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) @@ -222,7 +231,6 @@ 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/swap_io.c b/mm/swap_io.c index 4bf210bd677e..602e9b871b30 100644 --- a/mm/swap_io.c +++ b/mm/swap_io.c @@ -238,6 +238,7 @@ 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); if (folio_free_swap(folio)) goto out_unlock; @@ -279,7 +280,7 @@ int swap_writeout(struct folio *folio, struct swap_iocb **swap_plug) return AOP_WRITEPAGE_ACTIVATE; } - __swap_writepage(folio, swap_plug); + sis->ops->write_folio(sis, folio, swap_plug); return 0; out_unlock: folio_unlock(folio); @@ -369,10 +370,11 @@ 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); @@ -405,8 +407,9 @@ 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; @@ -425,8 +428,9 @@ 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; @@ -442,29 +446,6 @@ 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 (scan_swap_map_slots), - * 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 (scan_swap_map_slots), - * 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; @@ -533,9 +514,10 @@ 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); @@ -567,8 +549,9 @@ 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; @@ -589,8 +572,9 @@ 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; @@ -604,6 +588,44 @@ 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 -1; + + return 0; +} + void swap_read_folio(struct folio *folio, struct swap_iocb **plug) { struct swap_info_struct *sis = __swap_entry_to_info(folio->swap); @@ -638,13 +660,7 @@ 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/swapfile.c b/mm/swapfile.c index 60e21414624b..7e1660f59c00 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -3413,6 +3413,11 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) goto bad_swap_unlock_inode; } + if (init_swap_ops(si)) { + error = -EINVAL; + goto bad_swap_unlock_inode; + } + si->max = maxpages; si->pages = maxpages - 1; nr_extents = setup_swap_extents(si, &span); diff --git a/mm/zswap.c b/mm/zswap.c index 16b2ef7223e1..d8930d9054df 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1061,7 +1061,7 @@ 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