[PATCH 02/12] swap: move boilerplate code into the core swap code

[Christoph Hellwig <hch@lst.de>]

Make the core swap code calculate sis->pages, nr_extents and the span,
re-set sis->max based on it and don't require passing the current offset
into the swap file to swap_add_extent as all that can trivially be
calculated internally.  Also truncate the spans based on the available
information.

All this removes a lot of boilerplate code in the callers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 Documentation/filesystems/locking.rst |   2 +-
 Documentation/filesystems/vfs.rst     |   2 +-
 fs/btrfs/inode.c                      |  58 ++-----------
 fs/ext4/inode.c                       |   5 +-
 fs/f2fs/data.c                        |  38 ++-------
 fs/iomap/swapfile.c                   |  58 +------------
 fs/nfs/file.c                         |   9 +-
 fs/ntfs/aops.c                        |   5 +-
 fs/smb/client/file.c                  |   5 +-
 fs/xfs/xfs_aops.c                     |   6 +-
 fs/zonefs/file.c                      |   5 +-
 include/linux/fs.h                    |   3 +-
 include/linux/iomap.h                 |   5 +-
 include/linux/swap.h                  |  11 ++-
 mm/page_io.c                          |  39 ++-------
 mm/swapfile.c                         | 116 ++++++++++++++++----------
 16 files changed, 121 insertions(+), 246 deletions(-)

diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
index 8421ea21bd35..f3658204d070 100644
--- a/Documentation/filesystems/locking.rst
+++ b/Documentation/filesystems/locking.rst
@@ -264,7 +264,7 @@ prototypes::
 	int (*launder_folio)(struct folio *);
 	bool (*is_partially_uptodate)(struct folio *, size_t from, size_t count);
 	int (*error_remove_folio)(struct address_space *, struct folio *);
-	int (*swap_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span)
+	int (*swap_activate)(struct swap_info_struct *sis, struct file *f)
 	int (*swap_deactivate)(struct file *);
 	int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter);
 
diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
index 7c753148af88..4092b2149a5d 100644
--- a/Documentation/filesystems/vfs.rst
+++ b/Documentation/filesystems/vfs.rst
@@ -774,7 +774,7 @@ cache in your filesystem.  The following members are defined:
 					       size_t count);
 		void (*is_dirty_writeback)(struct folio *, bool *, bool *);
 		int (*error_remove_folio)(struct mapping *mapping, struct folio *);
-		int (*swap_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span)
+		int (*swap_activate)(struct swap_info_struct *sis, struct file *f);
 		int (*swap_deactivate)(struct file *);
 		int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter);
 	};
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 906d5c21ebc4..198d87e6f19a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -10204,51 +10204,17 @@ struct btrfs_swap_info {
 	u64 start;
 	u64 block_start;
 	u64 block_len;
-	u64 lowest_ppage;
-	u64 highest_ppage;
-	unsigned long nr_pages;
-	int nr_extents;
 };
 
 static int btrfs_add_swap_extent(struct swap_info_struct *sis,
 				 struct btrfs_swap_info *bsi)
 {
-	unsigned long nr_pages;
-	unsigned long max_pages;
-	u64 first_ppage, first_ppage_reported, next_ppage;
-	int ret;
-
-	/*
-	 * Our swapfile may have had its size extended after the swap header was
-	 * written. In that case activating the swapfile should not go beyond
-	 * the max size set in the swap header.
-	 */
-	if (bsi->nr_pages >= sis->max)
-		return 0;
+	u64 first_ppage, next_ppage;
 
-	max_pages = sis->max - bsi->nr_pages;
 	first_ppage = PAGE_ALIGN(bsi->block_start) >> PAGE_SHIFT;
 	next_ppage = PAGE_ALIGN_DOWN(bsi->block_start + bsi->block_len) >> PAGE_SHIFT;
 
-	if (first_ppage >= next_ppage)
-		return 0;
-	nr_pages = next_ppage - first_ppage;
-	nr_pages = min(nr_pages, max_pages);
-
-	first_ppage_reported = first_ppage;
-	if (bsi->start == 0)
-		first_ppage_reported++;
-	if (bsi->lowest_ppage > first_ppage_reported)
-		bsi->lowest_ppage = first_ppage_reported;
-	if (bsi->highest_ppage < (next_ppage - 1))
-		bsi->highest_ppage = next_ppage - 1;
-
-	ret = add_swap_extent(sis, bsi->nr_pages, nr_pages, first_ppage);
-	if (ret < 0)
-		return ret;
-	bsi->nr_extents += ret;
-	bsi->nr_pages += nr_pages;
-	return 0;
+	return add_swap_extent(sis, next_ppage - first_ppage, first_ppage);
 }
 
 static void btrfs_swap_deactivate(struct file *file)
@@ -10259,8 +10225,7 @@ static void btrfs_swap_deactivate(struct file *file)
 	atomic_dec(&BTRFS_I(inode)->root->nr_swapfiles);
 }
 
-static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file,
-			       sector_t *span)
+static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file)
 {
 	struct inode *inode = file_inode(file);
 	struct btrfs_root *root = BTRFS_I(inode)->root;
@@ -10269,9 +10234,7 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file,
 	struct extent_state *cached_state = NULL;
 	struct btrfs_chunk_map *map = NULL;
 	struct btrfs_device *device = NULL;
-	struct btrfs_swap_info bsi = {
-		.lowest_ppage = (sector_t)-1ULL,
-	};
+	struct btrfs_swap_info bsi = {};
 	struct btrfs_backref_share_check_ctx *backref_ctx = NULL;
 	struct btrfs_path *path = NULL;
 	int ret = 0;
@@ -10570,23 +10533,16 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file,
 	up_write(&BTRFS_I(inode)->i_mmap_lock);
 	btrfs_free_backref_share_ctx(backref_ctx);
 	btrfs_free_path(path);
-	if (ret)
-		return ret;
-
-	if (device)
+	if (!ret && device)
 		sis->bdev = device->bdev;
-	*span = bsi.highest_ppage - bsi.lowest_ppage + 1;
-	sis->max = bsi.nr_pages;
-	sis->pages = bsi.nr_pages - 1;
-	return bsi.nr_extents;
+	return ret;
 }
 #else
 static void btrfs_swap_deactivate(struct file *file)
 {
 }
 
-static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file,
-			       sector_t *span)
+static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c2c2d6ac7f3d..ca7bac4a8b4a 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3940,10 +3940,9 @@ static bool ext4_dirty_folio(struct address_space *mapping, struct folio *folio)
 }
 
 static int ext4_iomap_swap_activate(struct swap_info_struct *sis,
-				    struct file *file, sector_t *span)
+				    struct file *file)
 {
-	return iomap_swapfile_activate(sis, file, span,
-				       &ext4_iomap_report_ops);
+	return iomap_swapfile_activate(sis, file, &ext4_iomap_report_ops);
 }
 
 static const struct address_space_operations ext4_aops = {
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 8d4f1e75dee3..86fabacc67e6 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -4249,7 +4249,7 @@ static int f2fs_migrate_blocks(struct inode *inode, block_t start_blk,
 }
 
 static int check_swap_activate(struct swap_info_struct *sis,
-				struct file *swap_file, sector_t *span)
+				struct file *swap_file)
 {
 	struct address_space *mapping = swap_file->f_mapping;
 	struct inode *inode = mapping->host;
@@ -4257,9 +4257,6 @@ static int check_swap_activate(struct swap_info_struct *sis,
 	block_t cur_lblock;
 	block_t last_lblock;
 	block_t pblock;
-	block_t lowest_pblock = -1;
-	block_t highest_pblock = 0;
-	int nr_extents = 0;
 	unsigned int nr_pblocks;
 	unsigned int blks_per_sec = BLKS_PER_SEC(sbi);
 	unsigned int not_aligned = 0;
@@ -4272,7 +4269,7 @@ static int check_swap_activate(struct swap_info_struct *sis,
 	cur_lblock = 0;
 	last_lblock = F2FS_BYTES_TO_BLK(i_size_read(inode));
 
-	while (cur_lblock < last_lblock && cur_lblock < sis->max) {
+	while (cur_lblock < last_lblock) {
 		struct f2fs_map_blocks map;
 		bool last_extent = false;
 retry:
@@ -4307,8 +4304,6 @@ static int check_swap_activate(struct swap_info_struct *sis,
 			not_aligned++;
 
 			nr_pblocks = roundup(nr_pblocks, blks_per_sec);
-			if (cur_lblock + nr_pblocks > sis->max)
-				nr_pblocks -= blks_per_sec;
 
 			/* this extent is last one */
 			if (!nr_pblocks) {
@@ -4328,31 +4323,14 @@ static int check_swap_activate(struct swap_info_struct *sis,
 			goto retry;
 		}
 
-		if (cur_lblock + nr_pblocks >= sis->max)
-			nr_pblocks = sis->max - cur_lblock;
-
-		if (cur_lblock) {	/* exclude the header page */
-			if (pblock < lowest_pblock)
-				lowest_pblock = pblock;
-			if (pblock + nr_pblocks - 1 > highest_pblock)
-				highest_pblock = pblock + nr_pblocks - 1;
-		}
-
 		/*
 		 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
 		 */
-		ret = add_swap_extent(sis, cur_lblock, nr_pblocks, pblock);
+		ret = add_swap_extent(sis, nr_pblocks, pblock);
 		if (ret < 0)
 			goto out;
-		nr_extents += ret;
 		cur_lblock += nr_pblocks;
 	}
-	ret = nr_extents;
-	*span = 1 + highest_pblock - lowest_pblock;
-	if (cur_lblock == 0)
-		cur_lblock = 1;	/* force Empty message */
-	sis->max = cur_lblock;
-	sis->pages = cur_lblock - 1;
 out:
 	if (not_aligned)
 		f2fs_warn(sbi, "Swapfile (%u) is not align to section: 1) creat(), 2) ioctl(F2FS_IOC_SET_PIN_FILE), 3) fallocate(%lu * N)",
@@ -4360,8 +4338,7 @@ static int check_swap_activate(struct swap_info_struct *sis,
 	return ret;
 }
 
-static int f2fs_swap_activate(struct swap_info_struct *sis, struct file *file,
-				sector_t *span)
+static int f2fs_swap_activate(struct swap_info_struct *sis, struct file *file)
 {
 	struct inode *inode = file_inode(file);
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
@@ -4391,14 +4368,14 @@ static int f2fs_swap_activate(struct swap_info_struct *sis, struct file *file,
 
 	f2fs_precache_extents(inode);
 
-	ret = check_swap_activate(sis, file, span);
+	ret = check_swap_activate(sis, file);
 	if (ret < 0)
 		return ret;
 
 	stat_inc_swapfile_inode(inode);
 	set_inode_flag(inode, FI_PIN_FILE);
 	f2fs_update_time(sbi, REQ_TIME);
-	return ret;
+	return 0;
 }
 
 static void f2fs_swap_deactivate(struct file *file)
@@ -4409,8 +4386,7 @@ static void f2fs_swap_deactivate(struct file *file)
 	clear_inode_flag(inode, FI_PIN_FILE);
 }
 #else
-static int f2fs_swap_activate(struct swap_info_struct *sis, struct file *file,
-				sector_t *span)
+static int f2fs_swap_activate(struct swap_info_struct *sis, struct file *file)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/fs/iomap/swapfile.c b/fs/iomap/swapfile.c
index 0db77c449467..f778b2c6c922 100644
--- a/fs/iomap/swapfile.c
+++ b/fs/iomap/swapfile.c
@@ -11,10 +11,7 @@
 struct iomap_swapfile_info {
 	struct iomap iomap;		/* accumulated iomap */
 	struct swap_info_struct *sis;
-	uint64_t lowest_ppage;		/* lowest physical addr seen (pages) */
-	uint64_t highest_ppage;		/* highest physical addr seen (pages) */
 	unsigned long nr_pages;		/* number of pages collected */
-	int nr_extents;			/* extent count */
 	struct file *file;
 };
 
@@ -27,16 +24,8 @@ struct iomap_swapfile_info {
 static int iomap_swapfile_add_extent(struct iomap_swapfile_info *isi)
 {
 	struct iomap *iomap = &isi->iomap;
-	unsigned long nr_pages;
-	unsigned long max_pages;
 	uint64_t first_ppage;
-	uint64_t first_ppage_reported;
 	uint64_t next_ppage;
-	int error;
-
-	if (unlikely(isi->nr_pages >= isi->sis->max))
-		return 0;
-	max_pages = isi->sis->max - isi->nr_pages;
 
 	/*
 	 * Round the start up and the end down so that the physical
@@ -45,33 +34,7 @@ static int iomap_swapfile_add_extent(struct iomap_swapfile_info *isi)
 	first_ppage = ALIGN(iomap->addr, PAGE_SIZE) >> PAGE_SHIFT;
 	next_ppage = ALIGN_DOWN(iomap->addr + iomap->length, PAGE_SIZE) >>
 			PAGE_SHIFT;
-
-	/* Skip too-short physical extents. */
-	if (first_ppage >= next_ppage)
-		return 0;
-	nr_pages = next_ppage - first_ppage;
-	nr_pages = min(nr_pages, max_pages);
-
-	/*
-	 * Calculate how much swap space we're adding; the first page contains
-	 * the swap header and doesn't count.  The mm still wants that first
-	 * page fed to add_swap_extent, however.
-	 */
-	first_ppage_reported = first_ppage;
-	if (iomap->offset == 0)
-		first_ppage_reported++;
-	if (isi->lowest_ppage > first_ppage_reported)
-		isi->lowest_ppage = first_ppage_reported;
-	if (isi->highest_ppage < (next_ppage - 1))
-		isi->highest_ppage = next_ppage - 1;
-
-	/* Add extent, set up for the next call. */
-	error = add_swap_extent(isi->sis, isi->nr_pages, nr_pages, first_ppage);
-	if (error < 0)
-		return error;
-	isi->nr_extents += error;
-	isi->nr_pages += nr_pages;
-	return 0;
+	return add_swap_extent(isi->sis, next_ppage - first_ppage, first_ppage);
 }
 
 static int iomap_swapfile_fail(struct iomap_swapfile_info *isi, const char *str)
@@ -138,8 +101,7 @@ static int iomap_swapfile_iter(struct iomap_iter *iter,
  * passed to the swapfile subsystem.
  */
 int iomap_swapfile_activate(struct swap_info_struct *sis,
-		struct file *swap_file, sector_t *pagespan,
-		const struct iomap_ops *ops)
+		struct file *swap_file, const struct iomap_ops *ops)
 {
 	struct inode *inode = swap_file->f_mapping->host;
 	struct iomap_iter iter = {
@@ -150,7 +112,6 @@ int iomap_swapfile_activate(struct swap_info_struct *sis,
 	};
 	struct iomap_swapfile_info isi = {
 		.sis = sis,
-		.lowest_ppage = (sector_t)-1ULL,
 		.file = swap_file,
 	};
 	int ret;
@@ -174,19 +135,6 @@ int iomap_swapfile_activate(struct swap_info_struct *sis,
 			return ret;
 	}
 
-	/*
-	 * If this swapfile doesn't contain even a single page-aligned
-	 * contiguous range of blocks, reject this useless swapfile to
-	 * prevent confusion later on.
-	 */
-	if (isi.nr_pages == 0) {
-		pr_warn("swapon: Cannot find a single usable page in file.\n");
-		return -EINVAL;
-	}
-
-	*pagespan = 1 + isi.highest_ppage - isi.lowest_ppage;
-	sis->max = isi.nr_pages;
-	sis->pages = isi.nr_pages - 1;
-	return isi.nr_extents;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(iomap_swapfile_activate);
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 25048a3c2364..74b401aa2b3a 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -567,8 +567,7 @@ static int nfs_launder_folio(struct folio *folio)
 	return ret;
 }
 
-static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file,
-						sector_t *span)
+static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file)
 {
 	unsigned long blocks;
 	long long isize;
@@ -589,19 +588,17 @@ static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file,
 	ret = rpc_clnt_swap_activate(clnt);
 	if (ret)
 		return ret;
-	ret = add_swap_extent(sis, 0, sis->max, 0);
+	ret = add_swap_extent(sis, sis->max, 0);
 	if (ret < 0) {
 		rpc_clnt_swap_deactivate(clnt);
 		return ret;
 	}
 
-	*span = sis->pages;
-
 	if (cl->rpc_ops->enable_swap)
 		cl->rpc_ops->enable_swap(inode);
 
 	sis->flags |= SWP_FS_OPS;
-	return ret;
+	return 0;
 }
 
 static void nfs_swap_deactivate(struct file *file)
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 1fbf832ad165..4b7d019bc6ed 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -271,10 +271,9 @@ static int ntfs_writepages(struct address_space *mapping,
 }
 
 static int ntfs_swap_activate(struct swap_info_struct *sis,
-		struct file *swap_file, sector_t *span)
+		struct file *swap_file)
 {
-	return iomap_swapfile_activate(sis, swap_file, span,
-			&ntfs_read_iomap_ops);
+	return iomap_swapfile_activate(sis, swap_file, &ntfs_read_iomap_ops);
 }
 
 const struct address_space_operations ntfs_aops = {
diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index 664a2c223089..11d4655ef490 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -3287,7 +3287,7 @@ void cifs_oplock_break(struct work_struct *work)
 }
 
 static int cifs_swap_activate(struct swap_info_struct *sis,
-			      struct file *swap_file, sector_t *span)
+			      struct file *swap_file)
 {
 	struct cifsFileInfo *cfile = swap_file->private_data;
 	struct inode *inode = swap_file->f_mapping->host;
@@ -3308,7 +3308,6 @@ static int cifs_swap_activate(struct swap_info_struct *sis,
 		pr_warn("swap activate: swapfile has holes\n");
 		return -EINVAL;
 	}
-	*span = sis->pages;
 
 	pr_warn_once("Swap support over SMB3 is experimental\n");
 
@@ -3329,7 +3328,7 @@ static int cifs_swap_activate(struct swap_info_struct *sis,
 	 */
 
 	sis->flags |= SWP_FS_OPS;
-	return add_swap_extent(sis, 0, sis->max, 0);
+	return add_swap_extent(sis, sis->max, 0);
 }
 
 static void cifs_swap_deactivate(struct file *file)
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index f279055fcea0..1e8662e0e7cd 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -799,8 +799,7 @@ xfs_vm_readahead(
 static int
 xfs_vm_swap_activate(
 	struct swap_info_struct		*sis,
-	struct file			*swap_file,
-	sector_t			*span)
+	struct file			*swap_file)
 {
 	struct xfs_inode		*ip = XFS_I(file_inode(swap_file));
 
@@ -838,8 +837,7 @@ xfs_vm_swap_activate(
 	 */
 	sis->bdev = xfs_inode_buftarg(ip)->bt_bdev;
 
-	return iomap_swapfile_activate(sis, swap_file, span,
-			&xfs_read_iomap_ops);
+	return iomap_swapfile_activate(sis, swap_file, &xfs_read_iomap_ops);
 }
 
 const struct address_space_operations xfs_address_space_operations = {
diff --git a/fs/zonefs/file.c b/fs/zonefs/file.c
index 5ada33f70bb4..214e4bf8e30a 100644
--- a/fs/zonefs/file.c
+++ b/fs/zonefs/file.c
@@ -168,7 +168,7 @@ static int zonefs_writepages(struct address_space *mapping,
 }
 
 static int zonefs_swap_activate(struct swap_info_struct *sis,
-				struct file *swap_file, sector_t *span)
+				struct file *swap_file)
 {
 	struct inode *inode = file_inode(swap_file);
 
@@ -178,8 +178,7 @@ static int zonefs_swap_activate(struct swap_info_struct *sis,
 		return -EINVAL;
 	}
 
-	return iomap_swapfile_activate(sis, swap_file, span,
-				       &zonefs_read_iomap_ops);
+	return iomap_swapfile_activate(sis, swap_file, &zonefs_read_iomap_ops);
 }
 
 const struct address_space_operations zonefs_file_aops = {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 11559c513dfb..b8b6f7a38f4d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -435,8 +435,7 @@ struct address_space_operations {
 	int (*error_remove_folio)(struct address_space *, struct folio *);
 
 	/* swapfile support */
-	int (*swap_activate)(struct swap_info_struct *sis, struct file *file,
-				sector_t *span);
+	int (*swap_activate)(struct swap_info_struct *sis, struct file *file);
 	void (*swap_deactivate)(struct file *file);
 	int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter);
 };
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 2c5685adf3a9..d82126e3d086 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -604,10 +604,9 @@ struct file;
 struct swap_info_struct;
 
 int iomap_swapfile_activate(struct swap_info_struct *sis,
-		struct file *swap_file, sector_t *pagespan,
-		const struct iomap_ops *ops);
+		struct file *swap_file, const struct iomap_ops *ops);
 #else
-# define iomap_swapfile_activate(sis, swapfile, pagespan, ops)	(-EIO)
+# define iomap_swapfile_activate(sis, swapfile, ops)	(-EIO)
 #endif /* CONFIG_SWAP */
 
 extern struct bio_set iomap_ioend_bioset;
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 7a09df6977a5..b8dfe2c6bc98 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -403,10 +403,9 @@ extern void __meminit kswapd_stop(int nid);
 
 #ifdef CONFIG_SWAP
 
-int add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
-		unsigned long nr_pages, sector_t start_block);
-int generic_swapfile_activate(struct swap_info_struct *, struct file *,
-		sector_t *);
+int add_swap_extent(struct swap_info_struct *sis, unsigned long nr_pages,
+		sector_t start_block);
+int generic_swapfile_activate(struct swap_info_struct *, struct file *);
 
 static inline unsigned long total_swapcache_pages(void)
 {
@@ -528,8 +527,8 @@ static inline bool folio_free_swap(struct folio *folio)
 }
 
 static inline int add_swap_extent(struct swap_info_struct *sis,
-				  unsigned long start_page,
-				  unsigned long nr_pages, sector_t start_block)
+		unsigned long start_page, unsigned long nr_pages,
+		sector_t start_block)
 {
 	return -EINVAL;
 }
diff --git a/mm/page_io.c b/mm/page_io.c
index 70cea9e24d2f..f30f36ec1ed0 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -76,19 +76,14 @@ static void end_swap_bio_read(struct bio *bio)
 }
 
 int generic_swapfile_activate(struct swap_info_struct *sis,
-				struct file *swap_file,
-				sector_t *span)
+				struct file *swap_file)
 {
 	struct address_space *mapping = swap_file->f_mapping;
 	struct inode *inode = mapping->host;
 	unsigned blocks_per_page;
-	unsigned long page_no;
 	unsigned blkbits;
 	sector_t probe_block;
 	sector_t last_block;
-	sector_t lowest_block = -1;
-	sector_t highest_block = 0;
-	int nr_extents = 0;
 	int ret;
 
 	blkbits = inode->i_blkbits;
@@ -99,10 +94,8 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
 	 * to be very smart.
 	 */
 	probe_block = 0;
-	page_no = 0;
 	last_block = i_size_read(inode) >> blkbits;
-	while ((probe_block + blocks_per_page) <= last_block &&
-			page_no < sis->max) {
+	while ((probe_block + blocks_per_page) <= last_block) {
 		unsigned block_in_page;
 		sector_t first_block;
 
@@ -137,38 +130,22 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
 			}
 		}
 
-		first_block >>= (PAGE_SHIFT - blkbits);
-		if (page_no) {	/* exclude the header page */
-			if (first_block < lowest_block)
-				lowest_block = first_block;
-			if (first_block > highest_block)
-				highest_block = first_block;
-		}
-
 		/*
 		 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
 		 */
-		ret = add_swap_extent(sis, page_no, 1, first_block);
+		ret = add_swap_extent(sis, 1,
+				first_block >> (PAGE_SHIFT - blkbits));
 		if (ret < 0)
-			goto out;
-		nr_extents += ret;
-		page_no++;
+			return ret;
 		probe_block += blocks_per_page;
 reprobe:
 		continue;
 	}
-	ret = nr_extents;
-	*span = 1 + highest_block - lowest_block;
-	if (page_no == 0)
-		page_no = 1;	/* force Empty message */
-	sis->max = page_no;
-	sis->pages = page_no - 1;
-out:
-	return ret;
+	return 0;
+
 bad_bmap:
 	pr_err("swapon: swapfile has holes\n");
-	ret = -EINVAL;
-	goto out;
+	return -EINVAL;
 }
 
 static bool is_folio_zero_filled(struct folio *folio)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index f7ebd97e28a3..158620fd2978 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2704,15 +2704,21 @@ static void destroy_swap_extents(struct swap_info_struct *sis,
  * Add a block range (and the corresponding page range) into this swapdev's
  * extent tree.
  *
- * This function rather assumes that it is called in ascending page order.
+ * Note that start_block is in units of PAGE_SIZE and not actually in block
+ * layer sectors as the sector_t would suggest.
  */
 int
-add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
-		unsigned long nr_pages, sector_t start_block)
+add_swap_extent(struct swap_info_struct *sis, unsigned long nr_pages,
+		sector_t start_block)
 {
 	struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL;
 	struct swap_extent *se;
-	struct swap_extent *new_se;
+
+	if (!nr_pages)
+		return 0;
+	if (unlikely(sis->pages >= sis->max))
+		return 0;
+	nr_pages = min(nr_pages, sis->max - sis->pages);
 
 	/*
 	 * place the new node at the right most since the
@@ -2725,25 +2731,25 @@ add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
 
 	if (parent) {
 		se = rb_entry(parent, struct swap_extent, rb_node);
-		BUG_ON(se->start_page + se->nr_pages != start_page);
-		if (se->start_block + se->nr_pages == start_block) {
-			/* Merge it */
-			se->nr_pages += nr_pages;
-			return 0;
-		}
+		if (WARN_ON_ONCE(se->start_page + se->nr_pages != sis->pages))
+			return -EINVAL;
+		if (se->start_block + se->nr_pages == start_block)
+			goto add;
 	}
 
 	/* No merge, insert a new extent. */
-	new_se = kmalloc_obj(*se);
-	if (new_se == NULL)
+	se = kzalloc_obj(*se);
+	if (!se)
 		return -ENOMEM;
-	new_se->start_page = start_page;
-	new_se->nr_pages = nr_pages;
-	new_se->start_block = start_block;
-
-	rb_link_node(&new_se->rb_node, parent, link);
-	rb_insert_color(&new_se->rb_node, &sis->swap_extent_root);
-	return 1;
+	rb_link_node(&se->rb_node, parent, link);
+	rb_insert_color(&se->rb_node, &sis->swap_extent_root);
+
+	se->start_page = sis->pages;
+	se->start_block = start_block;
+add:
+	se->nr_pages += nr_pages;
+	sis->pages += nr_pages;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(add_swap_extent);
 
@@ -2775,20 +2781,17 @@ EXPORT_SYMBOL_GPL(add_swap_extent);
  * extents in the rbtree. - akpm.
  */
 static int setup_swap_extents(struct swap_info_struct *sis,
-			      struct file *swap_file, sector_t *span)
+			      struct file *swap_file)
 {
 	struct address_space *mapping = swap_file->f_mapping;
 	struct inode *inode = mapping->host;
 	int ret;
 
-	if (S_ISBLK(inode->i_mode)) {
-		ret = add_swap_extent(sis, 0, sis->max, 0);
-		*span = sis->pages;
-		return ret;
-	}
+	if (S_ISBLK(inode->i_mode))
+		return add_swap_extent(sis, sis->max, 0);
 
 	if (mapping->a_ops->swap_activate) {
-		ret = mapping->a_ops->swap_activate(sis, swap_file, span);
+		ret = mapping->a_ops->swap_activate(sis, swap_file);
 		if (ret < 0)
 			return ret;
 		sis->flags |= SWP_ACTIVATED;
@@ -2800,7 +2803,7 @@ static int setup_swap_extents(struct swap_info_struct *sis,
 		return ret;
 	}
 
-	return generic_swapfile_activate(sis, swap_file, span);
+	return generic_swapfile_activate(sis, swap_file);
 }
 
 static void _enable_swap_info(struct swap_info_struct *si)
@@ -3428,6 +3431,40 @@ static int setup_swap_clusters_info(struct swap_info_struct *si,
 	return err;
 }
 
+static void swap_print_info(struct swap_info_struct *si, const char *name)
+{
+	unsigned int nr_extents = 0;
+	u64 lowest_ppage = (u64)-1;
+	u64 highest_ppage = 0;
+	struct swap_extent *se;
+
+	/*
+	 * Calculate how much swap space we're adding; the first page contains
+	 * the swap header and doesn't count.
+	 */
+	for (se = first_se(si); se; se = next_se(se)) {
+		u64 first_ppage = se->start_block;
+		u64 next_ppage = se->start_block + se->nr_pages;
+
+		if (se->start_page == 0)
+			first_ppage++;
+
+		if (lowest_ppage > first_ppage)
+			lowest_ppage = first_ppage;
+		if (highest_ppage < next_ppage - 1)
+			highest_ppage = next_ppage - 1;
+		nr_extents++;
+	}
+
+	pr_info("Adding %uk swap on %s.  Priority:%d extents:%d across:%lluk %s%s%s%s\n",
+		K(si->pages), name, si->prio, nr_extents,
+		K(highest_ppage - lowest_ppage),
+		(si->flags & SWP_SOLIDSTATE) ? "SS" : "",
+		(si->flags & SWP_DISCARDABLE) ? "D" : "",
+		(si->flags & SWP_AREA_DISCARD) ? "s" : "",
+		(si->flags & SWP_PAGE_DISCARD) ? "c" : "");
+}
+
 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 {
 	struct swap_info_struct *si;
@@ -3437,8 +3474,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	int prio;
 	int error;
 	union swap_header *swap_header;
-	int nr_extents;
-	sector_t span;
 	struct folio *folio = NULL;
 	struct inode *inode = NULL;
 	bool inced_nr_rotate_swap = false;
@@ -3510,24 +3545,25 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 	swap_header = kmap_local_folio(folio, 0);
 
+	si->pages = 0;
 	si->max = read_swap_header(si, swap_header, inode);
 	if (unlikely(!si->max)) {
 		error = -EINVAL;
 		goto bad_swap_unlock_inode;
 	}
 
-	si->pages = si->max - 1;
-	nr_extents = setup_swap_extents(si, swap_file, &span);
-	if (nr_extents < 0) {
-		error = nr_extents;
+	error = setup_swap_extents(si, swap_file);
+	if (error < 0)
 		goto bad_swap_unlock_inode;
-	}
-	if (si->pages != si->max - 1) {
-		pr_err("swap:%u != (max:%u - 1)\n", si->pages, si->max);
+	if (si->pages != si->max) {
+		pr_err("swap:%u != (max:%u)\n", si->pages, si->max);
 		error = -EINVAL;
 		goto bad_swap_unlock_inode;
 	}
 
+	/* Remove the first page countaining the swap header. */
+	si->pages--;
+
 	/* Set up the swap cluster info */
 	error = setup_swap_clusters_info(si, swap_header);
 	if (error)
@@ -3624,13 +3660,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	/* Sets SWP_WRITEOK, resurrect the percpu ref, expose the swap device */
 	enable_swap_info(si);
 
-	pr_info("Adding %uk swap on %s.  Priority:%d extents:%d across:%lluk %s%s%s%s\n",
-		K(si->pages), name->name, si->prio, nr_extents,
-		K((unsigned long long)span),
-		(si->flags & SWP_SOLIDSTATE) ? "SS" : "",
-		(si->flags & SWP_DISCARDABLE) ? "D" : "",
-		(si->flags & SWP_AREA_DISCARD) ? "s" : "",
-		(si->flags & SWP_PAGE_DISCARD) ? "c" : "");
+	swap_print_info(si, name->name);
 
 	mutex_unlock(&swapon_mutex);
 	atomic_inc(&proc_poll_event);
-- 
2.53.0