Re: [PATCH v8 20/20] erofs: add 'fsid' mount option

[Gao Xiang]

On Wed, Apr 06, 2022 at 03:56:12PM +0800, Jeffle Xu wrote:
> Introduce 'fsid' mount option to enable on-demand read sementics, in
> which case, erofs will be mounted from data blobs. Users could specify
> the name of primary data blob by this mount option.
> 
> Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
> ---
>  fs/erofs/super.c | 48 ++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 42 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index a5e4de60a0d8..292b4a70ce19 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -398,6 +398,7 @@ enum {
>  	Opt_dax,
>  	Opt_dax_enum,
>  	Opt_device,
> +	Opt_fsid,
>  	Opt_err
>  };
>  
> @@ -422,6 +423,7 @@ static const struct fs_parameter_spec erofs_fs_parameters[] = {
>  	fsparam_flag("dax",             Opt_dax),
>  	fsparam_enum("dax",		Opt_dax_enum, erofs_dax_param_enums),
>  	fsparam_string("device",	Opt_device),
> +	fsparam_string("fsid",		Opt_fsid),
>  	{}
>  };
>  
> @@ -517,6 +519,16 @@ static int erofs_fc_parse_param(struct fs_context *fc,
>  		}
>  		++ctx->devs->extra_devices;
>  		break;
> +	case Opt_fsid:
> +#ifdef CONFIG_EROFS_FS_ONDEMAND
> +		kfree(ctx->opt.fsid);
> +		ctx->opt.fsid = kstrdup(param->string, GFP_KERNEL);
> +		if (!ctx->opt.fsid)
> +			return -ENOMEM;
> +#else
> +		errorfc(fc, "fsid option not supported");
> +#endif
> +		break;
>  	default:
>  		return -ENOPARAM;
>  	}
> @@ -597,9 +609,14 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>  	sb->s_maxbytes = MAX_LFS_FILESIZE;
>  	sb->s_op = &erofs_sops;
>  
> -	if (!sb_set_blocksize(sb, EROFS_BLKSIZ)) {
> -		erofs_err(sb, "failed to set erofs blksize");
> -		return -EINVAL;
> +	if (erofs_is_fscache_mode(sb)) {
> +		sb->s_blocksize = EROFS_BLKSIZ;
> +		sb->s_blocksize_bits = LOG_BLOCK_SIZE;
> +	} else {
> +		if (!sb_set_blocksize(sb, EROFS_BLKSIZ)) {
> +			erofs_err(sb, "failed to set erofs blksize");
> +			return -EINVAL;
> +		}
>  	}
>  
>  	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
> @@ -608,7 +625,7 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>  
>  	sb->s_fs_info = sbi;
>  	sbi->opt = ctx->opt;
> -	sbi->dax_dev = fs_dax_get_by_bdev(sb->s_bdev, &sbi->dax_part_off);
> +	ctx->opt.fsid = NULL;
>  	sbi->devs = ctx->devs;
>  	ctx->devs = NULL;
>  
> @@ -625,6 +642,8 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>  		err = super_setup_bdi(sb);
>  		if (err)
>  			return err;
> +	} else {
> +		sbi->dax_dev = fs_dax_get_by_bdev(sb->s_bdev, &sbi->dax_part_off);

It should go with the previous patch? And even over long line here.

Thanks,
Gao Xiang

>  	}
>  
>  	err = erofs_read_superblock(sb);
> @@ -684,6 +703,11 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>  
>  static int erofs_fc_get_tree(struct fs_context *fc)
>  {
> +	struct erofs_fs_context *ctx = fc->fs_private;
> +
> +	if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && ctx->opt.fsid)
> +		return get_tree_nodev(fc, erofs_fc_fill_super);
> +
>  	return get_tree_bdev(fc, erofs_fc_fill_super);
>  }
>  
> @@ -733,6 +757,7 @@ static void erofs_fc_free(struct fs_context *fc)
>  	struct erofs_fs_context *ctx = fc->fs_private;
>  
>  	erofs_free_dev_context(ctx->devs);
> +	kfree(ctx->opt.fsid);
>  	kfree(ctx);
>  }
>  
> @@ -773,7 +798,10 @@ static void erofs_kill_sb(struct super_block *sb)
>  
>  	WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);
>  
> -	kill_block_super(sb);
> +	if (erofs_is_fscache_mode(sb))
> +		generic_shutdown_super(sb);
> +	else
> +		kill_block_super(sb);
>  
>  	sbi = EROFS_SB(sb);
>  	if (!sbi)
> @@ -783,6 +811,7 @@ static void erofs_kill_sb(struct super_block *sb)
>  	fs_put_dax(sbi->dax_dev);
>  	erofs_fscache_unregister_cookie(&sbi->s_fscache);
>  	erofs_fscache_unregister_fs(sb);
> +	kfree(sbi->opt.fsid);
>  	kfree(sbi);
>  	sb->s_fs_info = NULL;
>  }
> @@ -884,7 +913,10 @@ static int erofs_statfs(struct dentry *dentry, struct kstatfs *buf)
>  {
>  	struct super_block *sb = dentry->d_sb;
>  	struct erofs_sb_info *sbi = EROFS_SB(sb);
> -	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
> +	u64 id = 0;
> +
> +	if (!erofs_is_fscache_mode(sb))
> +		id = huge_encode_dev(sb->s_bdev->bd_dev);
>  
>  	buf->f_type = sb->s_magic;
>  	buf->f_bsize = EROFS_BLKSIZ;
> @@ -929,6 +961,10 @@ static int erofs_show_options(struct seq_file *seq, struct dentry *root)
>  		seq_puts(seq, ",dax=always");
>  	if (test_opt(opt, DAX_NEVER))
>  		seq_puts(seq, ",dax=never");
> +#ifdef CONFIG_EROFS_FS_ONDEMAND
> +	if (opt->fsid)
> +		seq_printf(seq, ",fsid=%s", opt->fsid);
> +#endif
>  	return 0;
>  }
>  
> -- 
> 2.27.0
>