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

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, May 12, 2026 at 07:35:18AM +0200, Christoph Hellwig wrote:
> 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>

Looks great to me.  I'm glad the weird @span parameter goes away with
this.

Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  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
> 
>