Re: [PATCH] fs: clean up usage of noop_dirty_folio

[Jan Kara]

On Sat 19-08-23 20:42:25, Xueshi Hu wrote:
> In folio_mark_dirty(), it will automatically fallback to
> noop_dirty_folio() if a_ops->dirty_folio is not registered.
> 
> As anon_aops, dev_dax_aops and fb_deferred_io_aops becames empty, remove
> them too.
> 
> Signed-off-by: Xueshi Hu <xueshi.hu@xxxxxxxxxx>

Yeah, looks sensible to me but for some callbacks we are oscilating between
all users having to provide some callback and providing some default
behavior for NULL callback. I don't have a strong opinion either way so
feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

But I guess let's see what Matthew thinks about this and what plans he has
so that we don't switch back again in the near future. Matthew?

								Honza

> ---
>  drivers/dax/device.c                | 5 -----
>  drivers/video/fbdev/core/fb_defio.c | 5 -----
>  fs/aio.c                            | 1 -
>  fs/ext2/inode.c                     | 1 -
>  fs/ext4/inode.c                     | 1 -
>  fs/fuse/dax.c                       | 1 -
>  fs/hugetlbfs/inode.c                | 1 -
>  fs/libfs.c                          | 5 -----
>  fs/xfs/xfs_aops.c                   | 1 -
>  include/linux/pagemap.h             | 1 -
>  mm/page-writeback.c                 | 6 +++---
>  mm/secretmem.c                      | 1 -
>  mm/shmem.c                          | 1 -
>  mm/swap_state.c                     | 1 -
>  14 files changed, 3 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/dax/device.c b/drivers/dax/device.c
> index 30665a3ff6ea..018aa9f88ec7 100644
> --- a/drivers/dax/device.c
> +++ b/drivers/dax/device.c
> @@ -345,10 +345,6 @@ static unsigned long dax_get_unmapped_area(struct file *filp,
>  	return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
>  }
>  
> -static const struct address_space_operations dev_dax_aops = {
> -	.dirty_folio	= noop_dirty_folio,
> -};
> -
>  static int dax_open(struct inode *inode, struct file *filp)
>  {
>  	struct dax_device *dax_dev = inode_dax(inode);
> @@ -358,7 +354,6 @@ static int dax_open(struct inode *inode, struct file *filp)
>  	dev_dbg(&dev_dax->dev, "trace\n");
>  	inode->i_mapping = __dax_inode->i_mapping;
>  	inode->i_mapping->host = __dax_inode;
> -	inode->i_mapping->a_ops = &dev_dax_aops;
>  	filp->f_mapping = inode->i_mapping;
>  	filp->f_wb_err = filemap_sample_wb_err(filp->f_mapping);
>  	filp->f_sb_err = file_sample_sb_err(filp);
> diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
> index 274f5d0fa247..08be3592281f 100644
> --- a/drivers/video/fbdev/core/fb_defio.c
> +++ b/drivers/video/fbdev/core/fb_defio.c
> @@ -221,10 +221,6 @@ static const struct vm_operations_struct fb_deferred_io_vm_ops = {
>  	.page_mkwrite	= fb_deferred_io_mkwrite,
>  };
>  
> -static const struct address_space_operations fb_deferred_io_aops = {
> -	.dirty_folio	= noop_dirty_folio,
> -};
> -
>  int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
>  {
>  	vma->vm_ops = &fb_deferred_io_vm_ops;
> @@ -307,7 +303,6 @@ void fb_deferred_io_open(struct fb_info *info,
>  {
>  	struct fb_deferred_io *fbdefio = info->fbdefio;
>  
> -	file->f_mapping->a_ops = &fb_deferred_io_aops;
>  	fbdefio->open_count++;
>  }
>  EXPORT_SYMBOL_GPL(fb_deferred_io_open);
> diff --git a/fs/aio.c b/fs/aio.c
> index 77e33619de40..4cf386f9cb1c 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -484,7 +484,6 @@ static int aio_migrate_folio(struct address_space *mapping, struct folio *dst,
>  #endif
>  
>  static const struct address_space_operations aio_ctx_aops = {
> -	.dirty_folio	= noop_dirty_folio,
>  	.migrate_folio	= aio_migrate_folio,
>  };
>  
> diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
> index 75983215c7a1..ce191bdf1c78 100644
> --- a/fs/ext2/inode.c
> +++ b/fs/ext2/inode.c
> @@ -971,7 +971,6 @@ const struct address_space_operations ext2_aops = {
>  static const struct address_space_operations ext2_dax_aops = {
>  	.writepages		= ext2_dax_writepages,
>  	.direct_IO		= noop_direct_IO,
> -	.dirty_folio		= noop_dirty_folio,
>  };
>  
>  /*
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 43775a6ca505..67c1710c01b0 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3561,7 +3561,6 @@ static const struct address_space_operations ext4_da_aops = {
>  static const struct address_space_operations ext4_dax_aops = {
>  	.writepages		= ext4_dax_writepages,
>  	.direct_IO		= noop_direct_IO,
> -	.dirty_folio		= noop_dirty_folio,
>  	.bmap			= ext4_bmap,
>  	.swap_activate		= ext4_iomap_swap_activate,
>  };
> diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
> index 8e74f278a3f6..50ca767cbd5e 100644
> --- a/fs/fuse/dax.c
> +++ b/fs/fuse/dax.c
> @@ -1326,7 +1326,6 @@ bool fuse_dax_inode_alloc(struct super_block *sb, struct fuse_inode *fi)
>  static const struct address_space_operations fuse_dax_file_aops  = {
>  	.writepages	= fuse_dax_writepages,
>  	.direct_IO	= noop_direct_IO,
> -	.dirty_folio	= noop_dirty_folio,
>  };
>  
>  static bool fuse_should_enable_dax(struct inode *inode, unsigned int flags)
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 7b17ccfa039d..5404286f0c13 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -1266,7 +1266,6 @@ static void hugetlbfs_destroy_inode(struct inode *inode)
>  static const struct address_space_operations hugetlbfs_aops = {
>  	.write_begin	= hugetlbfs_write_begin,
>  	.write_end	= hugetlbfs_write_end,
> -	.dirty_folio	= noop_dirty_folio,
>  	.migrate_folio  = hugetlbfs_migrate_folio,
>  	.error_remove_page	= hugetlbfs_error_remove_page,
>  };
> diff --git a/fs/libfs.c b/fs/libfs.c
> index 5b851315eeed..982f220a9ee3 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -627,7 +627,6 @@ const struct address_space_operations ram_aops = {
>  	.read_folio	= simple_read_folio,
>  	.write_begin	= simple_write_begin,
>  	.write_end	= simple_write_end,
> -	.dirty_folio	= noop_dirty_folio,
>  };
>  EXPORT_SYMBOL(ram_aops);
>  
> @@ -1231,16 +1230,12 @@ EXPORT_SYMBOL(kfree_link);
>  
>  struct inode *alloc_anon_inode(struct super_block *s)
>  {
> -	static const struct address_space_operations anon_aops = {
> -		.dirty_folio	= noop_dirty_folio,
> -	};
>  	struct inode *inode = new_inode_pseudo(s);
>  
>  	if (!inode)
>  		return ERR_PTR(-ENOMEM);
>  
>  	inode->i_ino = get_next_ino();
> -	inode->i_mapping->a_ops = &anon_aops;
>  
>  	/*
>  	 * Mark the inode dirty from the very beginning,
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 451942fb38ec..300acea9ee63 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -590,6 +590,5 @@ const struct address_space_operations xfs_address_space_operations = {
>  
>  const struct address_space_operations xfs_dax_aops = {
>  	.writepages		= xfs_dax_writepages,
> -	.dirty_folio		= noop_dirty_folio,
>  	.swap_activate		= xfs_iomap_swapfile_activate,
>  };
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 716953ee1ebd..9de3be51dee2 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -1074,7 +1074,6 @@ bool folio_clear_dirty_for_io(struct folio *folio);
>  bool clear_page_dirty_for_io(struct page *page);
>  void folio_invalidate(struct folio *folio, size_t offset, size_t length);
>  int __set_page_dirty_nobuffers(struct page *page);
> -bool noop_dirty_folio(struct address_space *mapping, struct folio *folio);
>  
>  #ifdef CONFIG_MIGRATION
>  int filemap_migrate_folio(struct address_space *mapping, struct folio *dst,
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index d3f42009bb70..638ec965cf0b 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2588,13 +2588,12 @@ int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
>  /*
>   * For address_spaces which do not use buffers nor write back.
>   */
> -bool noop_dirty_folio(struct address_space *mapping, struct folio *folio)
> +static bool noop_dirty_folio(struct address_space *mapping, struct folio *folio)
>  {
>  	if (!folio_test_dirty(folio))
>  		return !folio_test_set_dirty(folio);
>  	return false;
>  }
> -EXPORT_SYMBOL(noop_dirty_folio);
>  
>  /*
>   * Helper function for set_page_dirty family.
> @@ -2799,7 +2798,8 @@ bool folio_mark_dirty(struct folio *folio)
>  		 */
>  		if (folio_test_reclaim(folio))
>  			folio_clear_reclaim(folio);
> -		return mapping->a_ops->dirty_folio(mapping, folio);
> +		if (mapping->a_ops->dirty_folio)
> +			return mapping->a_ops->dirty_folio(mapping, folio);
>  	}
>  
>  	return noop_dirty_folio(mapping, folio);
> diff --git a/mm/secretmem.c b/mm/secretmem.c
> index 86442a15d12f..3fe1c35f9c8d 100644
> --- a/mm/secretmem.c
> +++ b/mm/secretmem.c
> @@ -157,7 +157,6 @@ static void secretmem_free_folio(struct folio *folio)
>  }
>  
>  const struct address_space_operations secretmem_aops = {
> -	.dirty_folio	= noop_dirty_folio,
>  	.free_folio	= secretmem_free_folio,
>  	.migrate_folio	= secretmem_migrate_folio,
>  };
> diff --git a/mm/shmem.c b/mm/shmem.c
> index f5af4b943e42..90a7c046894a 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -4088,7 +4088,6 @@ static int shmem_error_remove_page(struct address_space *mapping,
>  
>  const struct address_space_operations shmem_aops = {
>  	.writepage	= shmem_writepage,
> -	.dirty_folio	= noop_dirty_folio,
>  #ifdef CONFIG_TMPFS
>  	.write_begin	= shmem_write_begin,
>  	.write_end	= shmem_write_end,
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index f8ea7015bad4..3666439487db 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -30,7 +30,6 @@
>   */
>  static const struct address_space_operations swap_aops = {
>  	.writepage	= swap_writepage,
> -	.dirty_folio	= noop_dirty_folio,
>  #ifdef CONFIG_MIGRATION
>  	.migrate_folio	= migrate_folio,
>  #endif
> -- 
> 2.40.1
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR