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Date:   Mon, 1 Apr 2019 11:25:16 -0400 (EDT)
From:   Nicolas Pitre <nico@fluxnic.net>
To:     David Howells <dhowells@redhat.com>
cc:     viro@zeniv.linux.org.uk, linux-mtd@lists.infradead.org,
        linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 48/68] vfs: Convert cramfs to use the new mount API
In-Reply-To: <155373039704.7602.6796835761744428479.stgit@warthog.procyon.org.uk>
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References: <155372999953.7602.13784796495137723805.stgit@warthog.procyon.org.uk> <155373039704.7602.6796835761744428479.stgit@warthog.procyon.org.uk>
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On Wed, 27 Mar 2019, David Howells wrote:

> Convert the cramfs filesystem to the new internal mount API as the old
> one will be obsoleted and removed.  This allows greater flexibility in
> communication of mount parameters between userspace, the VFS and the
> filesystem.
> 
> See Documentation/filesystems/mount_api.txt for more information.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Nicolas Pitre <nico@linaro.org>
> cc: linux-mtd@lists.infradead.org
> cc: linux-block@vger.kernel.org

Tested-by: Nicolas Pitre <nico@fluxnic.net>
Acked-by: Nicolas Pitre <nico@fluxnic.net>


> ---
> 
>  fs/cramfs/inode.c |   69 ++++++++++++++++++++++++++++++-----------------------
>  1 file changed, 39 insertions(+), 30 deletions(-)
> 
> diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> index 9352487bd0fc..2ee89a353d64 100644
> --- a/fs/cramfs/inode.c
> +++ b/fs/cramfs/inode.c
> @@ -24,6 +24,7 @@
>  #include <linux/blkdev.h>
>  #include <linux/mtd/mtd.h>
>  #include <linux/mtd/super.h>
> +#include <linux/fs_context.h>
>  #include <linux/slab.h>
>  #include <linux/vfs.h>
>  #include <linux/mutex.h>
> @@ -506,18 +507,19 @@ static void cramfs_kill_sb(struct super_block *sb)
>  	kfree(sbi);
>  }
>  
> -static int cramfs_remount(struct super_block *sb, int *flags, char *data)
> +static int cramfs_reconfigure(struct fs_context *fc)
>  {
> -	sync_filesystem(sb);
> -	*flags |= SB_RDONLY;
> +	sync_filesystem(fc->root->d_sb);
> +	fc->sb_flags |= SB_RDONLY;
>  	return 0;
>  }
>  
> -static int cramfs_read_super(struct super_block *sb,
> -			     struct cramfs_super *super, int silent)
> +static int cramfs_read_super(struct super_block *sb, struct fs_context *fc,
> +			     struct cramfs_super *super)
>  {
>  	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
>  	unsigned long root_offset;
> +	bool silent = fc->sb_flags & SB_SILENT;
>  
>  	/* We don't know the real size yet */
>  	sbi->size = PAGE_SIZE;
> @@ -532,7 +534,7 @@ static int cramfs_read_super(struct super_block *sb,
>  		/* check for wrong endianness */
>  		if (super->magic == CRAMFS_MAGIC_WEND) {
>  			if (!silent)
> -				pr_err("wrong endianness\n");
> +				errorf(fc, "cramfs: wrong endianness");
>  			return -EINVAL;
>  		}
>  
> @@ -544,22 +546,22 @@ static int cramfs_read_super(struct super_block *sb,
>  		mutex_unlock(&read_mutex);
>  		if (super->magic != CRAMFS_MAGIC) {
>  			if (super->magic == CRAMFS_MAGIC_WEND && !silent)
> -				pr_err("wrong endianness\n");
> +				errorf(fc, "cramfs: wrong endianness");
>  			else if (!silent)
> -				pr_err("wrong magic\n");
> +				errorf(fc, "cramfs: wrong magic");
>  			return -EINVAL;
>  		}
>  	}
>  
>  	/* get feature flags first */
>  	if (super->flags & ~CRAMFS_SUPPORTED_FLAGS) {
> -		pr_err("unsupported filesystem features\n");
> +		errorf(fc, "cramfs: unsupported filesystem features");
>  		return -EINVAL;
>  	}
>  
>  	/* Check that the root inode is in a sane state */
>  	if (!S_ISDIR(super->root.mode)) {
> -		pr_err("root is not a directory\n");
> +		errorf(fc, "cramfs: root is not a directory");
>  		return -EINVAL;
>  	}
>  	/* correct strange, hard-coded permissions of mkcramfs */
> @@ -578,12 +580,12 @@ static int cramfs_read_super(struct super_block *sb,
>  	sbi->magic = super->magic;
>  	sbi->flags = super->flags;
>  	if (root_offset == 0)
> -		pr_info("empty filesystem");
> +		infof(fc, "cramfs: empty filesystem");
>  	else if (!(super->flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
>  		 ((root_offset != sizeof(struct cramfs_super)) &&
>  		  (root_offset != 512 + sizeof(struct cramfs_super))))
>  	{
> -		pr_err("bad root offset %lu\n", root_offset);
> +		errorf(fc, "cramfs: bad root offset %lu", root_offset);
>  		return -EINVAL;
>  	}
>  
> @@ -607,8 +609,7 @@ static int cramfs_finalize_super(struct super_block *sb,
>  	return 0;
>  }
>  
> -static int cramfs_blkdev_fill_super(struct super_block *sb, void *data,
> -				    int silent)
> +static int cramfs_blkdev_fill_super(struct super_block *sb, struct fs_context *fc)
>  {
>  	struct cramfs_sb_info *sbi;
>  	struct cramfs_super super;
> @@ -623,14 +624,13 @@ static int cramfs_blkdev_fill_super(struct super_block *sb, void *data,
>  	for (i = 0; i < READ_BUFFERS; i++)
>  		buffer_blocknr[i] = -1;
>  
> -	err = cramfs_read_super(sb, &super, silent);
> +	err = cramfs_read_super(sb, fc, &super);
>  	if (err)
>  		return err;
>  	return cramfs_finalize_super(sb, &super.root);
>  }
>  
> -static int cramfs_mtd_fill_super(struct super_block *sb, void *data,
> -				 int silent)
> +static int cramfs_mtd_fill_super(struct super_block *sb, struct fs_context *fc)
>  {
>  	struct cramfs_sb_info *sbi;
>  	struct cramfs_super super;
> @@ -652,7 +652,7 @@ static int cramfs_mtd_fill_super(struct super_block *sb, void *data,
>  
>  	pr_info("checking physical address %pap for linear cramfs image\n",
>  		&sbi->linear_phys_addr);
> -	err = cramfs_read_super(sb, &super, silent);
> +	err = cramfs_read_super(sb, fc, &super);
>  	if (err)
>  		return err;
>  
> @@ -947,32 +947,41 @@ static const struct inode_operations cramfs_dir_inode_operations = {
>  };
>  
>  static const struct super_operations cramfs_ops = {
> -	.remount_fs	= cramfs_remount,
>  	.statfs		= cramfs_statfs,
>  };
>  
> -static struct dentry *cramfs_mount(struct file_system_type *fs_type, int flags,
> -				   const char *dev_name, void *data)
> +static int cramfs_get_tree(struct fs_context *fc)
>  {
> -	struct dentry *ret = ERR_PTR(-ENOPROTOOPT);
> +	int ret = -ENOPROTOOPT;
>  
>  	if (IS_ENABLED(CONFIG_CRAMFS_MTD)) {
> -		ret = mount_mtd(fs_type, flags, dev_name, data,
> -				cramfs_mtd_fill_super);
> -		if (!IS_ERR(ret))
> +		ret = vfs_get_mtd_super(fc, cramfs_mtd_fill_super);
> +		if (ret < 0)
>  			return ret;
>  	}
> -	if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV)) {
> -		ret = mount_bdev(fs_type, flags, dev_name, data,
> -				 cramfs_blkdev_fill_super);
> -	}
> +	if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
> +		ret = vfs_get_block_super(fc, cramfs_blkdev_fill_super);
>  	return ret;
>  }
>  
> +static const struct fs_context_operations cramfs_context_ops = {
> +	.get_tree	= cramfs_get_tree,
> +	.reconfigure	= cramfs_reconfigure,
> +};
> +
> +/*
> + * Set up the filesystem mount context.
> + */
> +static int cramfs_init_fs_context(struct fs_context *fc)
> +{
> +	fc->ops = &cramfs_context_ops;
> +	return 0;
> +}
> +
>  static struct file_system_type cramfs_fs_type = {
>  	.owner		= THIS_MODULE,
>  	.name		= "cramfs",
> -	.mount		= cramfs_mount,
> +	.init_fs_context = cramfs_init_fs_context,
>  	.kill_sb	= cramfs_kill_sb,
>  	.fs_flags	= FS_REQUIRES_DEV,
>  };
> 
>