Re: [PATCH v2 03/28] fs: Remove FS_THP_SUPPORT

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

On Mon, Nov 08, 2021 at 04:05:26AM +0000, Matthew Wilcox (Oracle) wrote:
> Instead of setting a bit in the fs_flags to set a bit in the
> address_space, set the bit in the address_space directly.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Makes sense,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/inode.c              |  2 --
>  include/linux/fs.h      |  1 -
>  include/linux/pagemap.h | 16 ++++++++++++++++
>  mm/shmem.c              |  3 ++-
>  4 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index 9abc88d7959c..d6386b6d5a6e 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -180,8 +180,6 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
>  	mapping->a_ops = &empty_aops;
>  	mapping->host = inode;
>  	mapping->flags = 0;
> -	if (sb->s_type->fs_flags & FS_THP_SUPPORT)
> -		__set_bit(AS_THP_SUPPORT, &mapping->flags);
>  	mapping->wb_err = 0;
>  	atomic_set(&mapping->i_mmap_writable, 0);
>  #ifdef CONFIG_READ_ONLY_THP_FOR_FS
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 4137a9bfae7a..3c2fcabf9d12 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2518,7 +2518,6 @@ struct file_system_type {
>  #define FS_USERNS_MOUNT		8	/* Can be mounted by userns root */
>  #define FS_DISALLOW_NOTIFY_PERM	16	/* Disable fanotify permission events */
>  #define FS_ALLOW_IDMAP         32      /* FS has been updated to handle vfs idmappings. */
> -#define FS_THP_SUPPORT		8192	/* Remove once all fs converted */
>  #define FS_RENAME_DOES_D_MOVE	32768	/* FS will handle d_move() during rename() internally. */
>  	int (*init_fs_context)(struct fs_context *);
>  	const struct fs_parameter_spec *parameters;
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index db2c3e3eb1cf..471f0c422831 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -126,6 +126,22 @@ static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
>  	m->gfp_mask = mask;
>  }
>  
> +/**
> + * mapping_set_large_folios() - Indicate the file supports multi-page folios.
> + * @mapping: The file.
> + *
> + * The filesystem should call this function in its inode constructor to
> + * indicate that the VFS can use multi-page folios to cache the contents
> + * of the file.
> + *
> + * Context: This should not be called while the inode is active as it
> + * is non-atomic.
> + */
> +static inline void mapping_set_large_folios(struct address_space *mapping)
> +{
> +	__set_bit(AS_THP_SUPPORT, &mapping->flags);
> +}
> +
>  static inline bool mapping_thp_support(struct address_space *mapping)
>  {
>  	return test_bit(AS_THP_SUPPORT, &mapping->flags);
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 23c91a8beb78..54422933fa2d 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2303,6 +2303,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
>  		INIT_LIST_HEAD(&info->swaplist);
>  		simple_xattrs_init(&info->xattrs);
>  		cache_no_acl(inode);
> +		mapping_set_large_folios(inode->i_mapping);
>  
>  		switch (mode & S_IFMT) {
>  		default:
> @@ -3920,7 +3921,7 @@ static struct file_system_type shmem_fs_type = {
>  	.parameters	= shmem_fs_parameters,
>  #endif
>  	.kill_sb	= kill_litter_super,
> -	.fs_flags	= FS_USERNS_MOUNT | FS_THP_SUPPORT,
> +	.fs_flags	= FS_USERNS_MOUNT,
>  };
>  
>  int __init shmem_init(void)
> -- 
> 2.33.0
>