Re: [PATCH] erofs: convert to use the new mount fs_context api

[Chao Yu]

Hi Xiang,

On 2019/12/26 10:16, Gao Xiang wrote:
> Hi Chao,
> 
> On Thu, Dec 26, 2019 at 09:50:04AM +0800, Chao Yu wrote:
>> Convert the erofs to use 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.
>>
> 
> How about adding this line...
> 
> Cc: David Howells <dhowells@xxxxxxxxxx>
> 
>> Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
>> Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
> 
> Could we resend this patch with the above commit message Cc fs_context
> owner as well since we are not quite sure if there are still some potential
> thing to consider... If he has some extra time and interest in it...

Sure, will resend soon...

Thanks,

> 
> Thanks,
> Gao Xiang
> 
>> ---
>>  fs/erofs/internal.h |   2 +-
>>  fs/erofs/super.c    | 249 +++++++++++++++++++++-----------------------
>>  2 files changed, 118 insertions(+), 133 deletions(-)
>>
>> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
>> index 1ed5beff7d11..a5fac25db6af 100644
>> --- a/fs/erofs/internal.h
>> +++ b/fs/erofs/internal.h
>> @@ -102,13 +102,13 @@ struct erofs_sb_info {
>>  #define set_opt(sbi, option)	((sbi)->mount_opt |= EROFS_MOUNT_##option)
>>  #define test_opt(sbi, option)	((sbi)->mount_opt & EROFS_MOUNT_##option)
>>  
>> -#ifdef CONFIG_EROFS_FS_ZIP
>>  enum {
>>  	EROFS_ZIP_CACHE_DISABLED,
>>  	EROFS_ZIP_CACHE_READAHEAD,
>>  	EROFS_ZIP_CACHE_READAROUND
>>  };
>>  
>> +#ifdef CONFIG_EROFS_FS_ZIP
>>  #define EROFS_LOCKED_MAGIC     (INT_MIN | 0xE0F510CCL)
>>  
>>  /* basic unit of the workstation of a super_block */
>> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
>> index 057e6d7b5b7f..b90713760885 100644
>> --- a/fs/erofs/super.c
>> +++ b/fs/erofs/super.c
>> @@ -10,6 +10,8 @@
>>  #include <linux/parser.h>
>>  #include <linux/seq_file.h>
>>  #include <linux/crc32c.h>
>> +#include <linux/fs_context.h>
>> +#include <linux/fs_parser.h>
>>  #include "xattr.h"
>>  
>>  #define CREATE_TRACE_POINTS
>> @@ -192,41 +194,6 @@ static int erofs_read_superblock(struct super_block *sb)
>>  	return ret;
>>  }
>>  
>> -#ifdef CONFIG_EROFS_FS_ZIP
>> -static int erofs_build_cache_strategy(struct super_block *sb,
>> -				      substring_t *args)
>> -{
>> -	struct erofs_sb_info *sbi = EROFS_SB(sb);
>> -	const char *cs = match_strdup(args);
>> -	int err = 0;
>> -
>> -	if (!cs) {
>> -		erofs_err(sb, "Not enough memory to store cache strategy");
>> -		return -ENOMEM;
>> -	}
>> -
>> -	if (!strcmp(cs, "disabled")) {
>> -		sbi->cache_strategy = EROFS_ZIP_CACHE_DISABLED;
>> -	} else if (!strcmp(cs, "readahead")) {
>> -		sbi->cache_strategy = EROFS_ZIP_CACHE_READAHEAD;
>> -	} else if (!strcmp(cs, "readaround")) {
>> -		sbi->cache_strategy = EROFS_ZIP_CACHE_READAROUND;
>> -	} else {
>> -		erofs_err(sb, "Unrecognized cache strategy \"%s\"", cs);
>> -		err = -EINVAL;
>> -	}
>> -	kfree(cs);
>> -	return err;
>> -}
>> -#else
>> -static int erofs_build_cache_strategy(struct super_block *sb,
>> -				      substring_t *args)
>> -{
>> -	erofs_info(sb, "EROFS compression is disabled, so cache strategy is ignored");
>> -	return 0;
>> -}
>> -#endif
>> -
>>  /* set up default EROFS parameters */
>>  static void erofs_default_options(struct erofs_sb_info *sbi)
>>  {
>> @@ -251,73 +218,79 @@ enum {
>>  	Opt_err
>>  };
>>  
>> -static match_table_t erofs_tokens = {
>> -	{Opt_user_xattr, "user_xattr"},
>> -	{Opt_nouser_xattr, "nouser_xattr"},
>> -	{Opt_acl, "acl"},
>> -	{Opt_noacl, "noacl"},
>> -	{Opt_cache_strategy, "cache_strategy=%s"},
>> -	{Opt_err, NULL}
>> +static const struct fs_parameter_spec erofs_param_specs[] = {
>> +	fsparam_flag("user_xattr",	Opt_user_xattr),
>> +	fsparam_flag("nouser_xattr",	Opt_nouser_xattr),
>> +	fsparam_flag("acl",		Opt_acl),
>> +	fsparam_flag("noacl",		Opt_noacl),
>> +	fsparam_enum("cache_strategy",	Opt_cache_strategy),
>> +	{}
>>  };
>>  
>> -static int erofs_parse_options(struct super_block *sb, char *options)
>> -{
>> -	substring_t args[MAX_OPT_ARGS];
>> -	char *p;
>> -	int err;
>> -
>> -	if (!options)
>> -		return 0;
>> +static const struct fs_parameter_enum erofs_param_enums[] = {
>> +	{ Opt_cache_strategy, "disabled",	EROFS_ZIP_CACHE_DISABLED },
>> +	{ Opt_cache_strategy, "readahead",	EROFS_ZIP_CACHE_READAHEAD},
>> +	{ Opt_cache_strategy, "readaround",	EROFS_ZIP_CACHE_READAROUND},
>> +	{}
>> +};
>>  
>> -	while ((p = strsep(&options, ","))) {
>> -		int token;
>> +static const struct fs_parameter_description erofs_fs_parameters = {
>> +	.name	= "erofs",
>> +	.specs	= erofs_param_specs,
>> +	.enums	= erofs_param_enums,
>> +};
>>  
>> -		if (!*p)
>> -			continue;
>> +static int erofs_fc_parse_param(struct fs_context *fc,
>> +				struct fs_parameter *param)
>> +{
>> +	struct erofs_sb_info *sbi __maybe_unused = fc->s_fs_info;
>> +	struct fs_parse_result result;
>> +	int opt;
>>  
>> -		args[0].to = args[0].from = NULL;
>> -		token = match_token(p, erofs_tokens, args);
>> +	opt = fs_parse(fc, &erofs_fs_parameters, param, &result);
>> +	if (opt < 0)
>> +		return opt;
>>  
>> -		switch (token) {
>> +	switch (opt) {
>>  #ifdef CONFIG_EROFS_FS_XATTR
>> -		case Opt_user_xattr:
>> -			set_opt(EROFS_SB(sb), XATTR_USER);
>> -			break;
>> -		case Opt_nouser_xattr:
>> -			clear_opt(EROFS_SB(sb), XATTR_USER);
>> -			break;
>> +	case Opt_user_xattr:
>> +		set_opt(sbi, XATTR_USER);
>> +		break;
>> +	case Opt_nouser_xattr:
>> +		clear_opt(sbi, XATTR_USER);
>> +		break;
>>  #else
>> -		case Opt_user_xattr:
>> -			erofs_info(sb, "user_xattr options not supported");
>> -			break;
>> -		case Opt_nouser_xattr:
>> -			erofs_info(sb, "nouser_xattr options not supported");
>> -			break;
>> +	case Opt_user_xattr:
>> +		invalf(fc, "erofs: user_xattr options not supported");
>> +		break;
>> +	case Opt_nouser_xattr:
>> +		invalf(fc, "erofs: nouser_xattr options not supported");
>> +		break;
>>  #endif
>>  #ifdef CONFIG_EROFS_FS_POSIX_ACL
>> -		case Opt_acl:
>> -			set_opt(EROFS_SB(sb), POSIX_ACL);
>> -			break;
>> -		case Opt_noacl:
>> -			clear_opt(EROFS_SB(sb), POSIX_ACL);
>> -			break;
>> +	case Opt_acl:
>> +		set_opt(sbi, POSIX_ACL);
>> +		break;
>> +	case Opt_noacl:
>> +		clear_opt(sbi, POSIX_ACL);
>> +		break;
>> +#else
>> +	case Opt_acl:
>> +		invalf(fc, "erofs: acl options not supported");
>> +		break;
>> +	case Opt_noacl:
>> +		invalf(fc, "erofs: noacl options not supported");
>> +		break;
>> +#endif
>> +	case Opt_cache_strategy:
>> +#ifdef CONFIG_EROFS_FS_ZIP
>> +		sbi->cache_strategy = result.uint_32;
>>  #else
>> -		case Opt_acl:
>> -			erofs_info(sb, "acl options not supported");
>> -			break;
>> -		case Opt_noacl:
>> -			erofs_info(sb, "noacl options not supported");
>> -			break;
>> +		errorf(fc, "erofs: compression not supported, cache strategy ignored");
>>  #endif
>> -		case Opt_cache_strategy:
>> -			err = erofs_build_cache_strategy(sb, args);
>> -			if (err)
>> -				return err;
>> -			break;
>> -		default:
>> -			erofs_err(sb, "Unrecognized mount option \"%s\" or missing value", p);
>> -			return -EINVAL;
>> -		}
>> +		break;
>> +	default:
>> +		return invalf(fc, "erofs: invalid mount option: %s", param->key);
>>  	}
>>  	return 0;
>>  }
>> @@ -381,7 +354,7 @@ static int erofs_init_managed_cache(struct super_block *sb)
>>  static int erofs_init_managed_cache(struct super_block *sb) { return 0; }
>>  #endif
>>  
>> -static int erofs_fill_super(struct super_block *sb, void *data, int silent)
>> +static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>>  {
>>  	struct inode *inode;
>>  	struct erofs_sb_info *sbi;
>> @@ -394,11 +367,7 @@ static int erofs_fill_super(struct super_block *sb, void *data, int silent)
>>  		return -EINVAL;
>>  	}
>>  
>> -	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>> -	if (!sbi)
>> -		return -ENOMEM;
>> -
>> -	sb->s_fs_info = sbi;
>> +	sbi = sb->s_fs_info;
>>  	err = erofs_read_superblock(sb);
>>  	if (err)
>>  		return err;
>> @@ -412,12 +381,6 @@ static int erofs_fill_super(struct super_block *sb, void *data, int silent)
>>  #ifdef CONFIG_EROFS_FS_XATTR
>>  	sb->s_xattr = erofs_xattr_handlers;
>>  #endif
>> -	/* set erofs default mount options */
>> -	erofs_default_options(sbi);
>> -
>> -	err = erofs_parse_options(sb, data);
>> -	if (err)
>> -		return err;
>>  
>>  	if (test_opt(sbi, POSIX_ACL))
>>  		sb->s_flags |= SB_POSIXACL;
>> @@ -450,15 +413,61 @@ static int erofs_fill_super(struct super_block *sb, void *data, int silent)
>>  	if (err)
>>  		return err;
>>  
>> -	erofs_info(sb, "mounted with opts: %s, root inode @ nid %llu.",
>> -		   (char *)data, ROOT_NID(sbi));
>> +	erofs_info(sb, "mounted with root inode @ nid %llu.", ROOT_NID(sbi));
>> +	return 0;
>> +}
>> +
>> +static int erofs_fc_get_tree(struct fs_context *fc)
>> +{
>> +	return get_tree_bdev(fc, erofs_fc_fill_super);
>> +}
>> +
>> +static int erofs_fc_reconfigure(struct fs_context *fc)
>> +{
>> +	struct super_block *sb = fc->root->d_sb;
>> +	struct erofs_sb_info *sbi = EROFS_SB(sb);
>> +
>> +	DBG_BUGON(!sb_rdonly(sb));
>> +
>> +	if (test_opt(sbi, POSIX_ACL))
>> +		fc->sb_flags |= SB_POSIXACL;
>> +	else
>> +		fc->sb_flags &= ~SB_POSIXACL;
>> +
>> +	fc->sb_flags |= SB_RDONLY;
>>  	return 0;
>>  }
>>  
>> -static struct dentry *erofs_mount(struct file_system_type *fs_type, int flags,
>> -				  const char *dev_name, void *data)
>> +static void erofs_fc_free(struct fs_context *fc)
>>  {
>> -	return mount_bdev(fs_type, flags, dev_name, data, erofs_fill_super);
>> +	/*
>> +	 * sbi stored in fs_context will be cleaned after transferring
>> +	 * to corresponding superblock on a successful new mount, or
>> +	 * free it here.
>> +	 */
>> +	kfree(fc->s_fs_info);
>> +}
>> +
>> +static const struct fs_context_operations erofs_context_ops = {
>> +	.parse_param	= erofs_fc_parse_param,
>> +	.get_tree       = erofs_fc_get_tree,
>> +	.reconfigure    = erofs_fc_reconfigure,
>> +	.free		= erofs_fc_free,
>> +};
>> +
>> +static int erofs_init_fs_context(struct fs_context *fc)
>> +{
>> +	struct erofs_sb_info *sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
>> +
>> +	if (!sbi)
>> +		return -ENOMEM;
>> +
>> +	/* set default mount options */
>> +	erofs_default_options(sbi);
>> +
>> +	fc->s_fs_info = sbi;
>> +	fc->ops = &erofs_context_ops;
>> +	return 0;
>>  }
>>  
>>  /*
>> @@ -497,7 +506,7 @@ static void erofs_put_super(struct super_block *sb)
>>  static struct file_system_type erofs_fs_type = {
>>  	.owner          = THIS_MODULE,
>>  	.name           = "erofs",
>> -	.mount          = erofs_mount,
>> +	.init_fs_context = erofs_init_fs_context,
>>  	.kill_sb        = erofs_kill_sb,
>>  	.fs_flags       = FS_REQUIRES_DEV,
>>  };
>> @@ -603,36 +612,12 @@ static int erofs_show_options(struct seq_file *seq, struct dentry *root)
>>  	return 0;
>>  }
>>  
>> -static int erofs_remount(struct super_block *sb, int *flags, char *data)
>> -{
>> -	struct erofs_sb_info *sbi = EROFS_SB(sb);
>> -	unsigned int org_mnt_opt = sbi->mount_opt;
>> -	int err;
>> -
>> -	DBG_BUGON(!sb_rdonly(sb));
>> -	err = erofs_parse_options(sb, data);
>> -	if (err)
>> -		goto out;
>> -
>> -	if (test_opt(sbi, POSIX_ACL))
>> -		sb->s_flags |= SB_POSIXACL;
>> -	else
>> -		sb->s_flags &= ~SB_POSIXACL;
>> -
>> -	*flags |= SB_RDONLY;
>> -	return 0;
>> -out:
>> -	sbi->mount_opt = org_mnt_opt;
>> -	return err;
>> -}
>> -
>>  const struct super_operations erofs_sops = {
>>  	.put_super = erofs_put_super,
>>  	.alloc_inode = erofs_alloc_inode,
>>  	.free_inode = erofs_free_inode,
>>  	.statfs = erofs_statfs,
>>  	.show_options = erofs_show_options,
>> -	.remount_fs = erofs_remount,
>>  };
>>  
>>  module_init(erofs_module_init);
>> -- 
>> 2.18.0.rc1
>>
> .
>