linux-kernel - Re: [PATCH V3 3/6] erofs: introduce 'domain

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Message-ID: <6644b9eb-d477-bbca-bbbe-b41776e38a46@linux.alibaba.com>
Date:   Thu, 15 Sep 2022 15:30:17 +0800
From:   JeffleXu <jefflexu@...ux.alibaba.com>
To:     Jia Zhu <zhujia.zj@...edance.com>, linux-erofs@...ts.ozlabs.org,
        xiang@...nel.org, chao@...nel.org
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        yinxin.x@...edance.com, huyue2@...lpad.com
Subject: Re: [PATCH V3 3/6] erofs: introduce 'domain_id' mount option



On 9/14/22 6:50 PM, Jia Zhu wrote:
> Introduce 'domain_id' mount option to enable shared domain sementics.
> In which case, the related cookie is shared if two mountpoints in the
> same domain have the same data blob. Users could specify the name of
> domain by this mount option.
> 
> Signed-off-by: Jia Zhu <zhujia.zj@...edance.com>

Could you please move this patch to the end of this patch set, so that
once the "domain_id" mount option is visible to users, this feature
really works?


> ---
>  fs/erofs/internal.h |  1 +
>  fs/erofs/super.c    | 17 +++++++++++++++++
>  fs/erofs/sysfs.c    | 19 +++++++++++++++++--
>  3 files changed, 35 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index aa71eb65e965..2d129c6b3027 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -76,6 +76,7 @@ struct erofs_mount_opts {
>  #endif
>  	unsigned int mount_opt;
>  	char *fsid;
> +	char *domain_id;
>  };

Indeed we can add @domain_id field into struct erofs_mount_opts in prep
for the following implementation of the domain_id feature. IOW, the
above change can be folded into patch 4, just like what [1] does.

[1]
https://github.com/torvalds/linux/commit/c6be2bd0a5dd91f98d6b5d2df2c79bc32993352c#diff-eee5fb30f4e83505af808386e84c953266d2fd2e76b6e66cb94cf6e849881240R77


>  
>  struct erofs_dev_context {
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index 7aa57dcebf31..856758ee4869 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -440,6 +440,7 @@ enum {
>  	Opt_dax_enum,
>  	Opt_device,
>  	Opt_fsid,
> +	Opt_domain_id,
>  	Opt_err
>  };
>  
> @@ -465,6 +466,7 @@ static const struct fs_parameter_spec erofs_fs_parameters[] = {
>  	fsparam_enum("dax",		Opt_dax_enum, erofs_dax_param_enums),
>  	fsparam_string("device",	Opt_device),
>  	fsparam_string("fsid",		Opt_fsid),
> +	fsparam_string("domain_id",	Opt_domain_id),
>  	{}
>  };
>  
> @@ -568,6 +570,16 @@ static int erofs_fc_parse_param(struct fs_context *fc,
>  			return -ENOMEM;
>  #else
>  		errorfc(fc, "fsid option not supported");
> +#endif
> +		break;
> +	case Opt_domain_id:
> +#ifdef CONFIG_EROFS_FS_ONDEMAND
> +		kfree(ctx->opt.domain_id);
> +		ctx->opt.domain_id = kstrdup(param->string, GFP_KERNEL);
> +		if (!ctx->opt.domain_id)
> +			return -ENOMEM;
> +#else
> +		errorfc(fc, "domain_id option not supported");
>  #endif
>  		break;
>  	default:
> @@ -695,6 +707,7 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>  	sb->s_fs_info = sbi;
>  	sbi->opt = ctx->opt;
>  	ctx->opt.fsid = NULL;
> +	ctx->opt.domain_id = NULL;
>  	sbi->devs = ctx->devs;
>  	ctx->devs = NULL;
>  
> @@ -834,6 +847,7 @@ static void erofs_fc_free(struct fs_context *fc)
>  
>  	erofs_free_dev_context(ctx->devs);
>  	kfree(ctx->opt.fsid);
> +	kfree(ctx->opt.domain_id);
>  	kfree(ctx);
>  }
>  
> @@ -887,6 +901,7 @@ static void erofs_kill_sb(struct super_block *sb)
>  	fs_put_dax(sbi->dax_dev, NULL);
>  	erofs_fscache_unregister_fs(sb);
>  	kfree(sbi->opt.fsid);
> +	kfree(sbi->opt.domain_id);
>  	kfree(sbi);
>  	sb->s_fs_info = NULL;
>  }
> @@ -1040,6 +1055,8 @@ static int erofs_show_options(struct seq_file *seq, struct dentry *root)
>  #ifdef CONFIG_EROFS_FS_ONDEMAND
>  	if (opt->fsid)
>  		seq_printf(seq, ",fsid=%s", opt->fsid);
> +	if (opt->domain_id)
> +		seq_printf(seq, ",domain_id=%s", opt->domain_id);
>  #endif
>  	return 0;
>  }
> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> index c1383e508bbe..341fb43ad587 100644
> --- a/fs/erofs/sysfs.c
> +++ b/fs/erofs/sysfs.c
> @@ -201,12 +201,27 @@ static struct kobject erofs_feat = {
>  int erofs_register_sysfs(struct super_block *sb)
>  {
>  	struct erofs_sb_info *sbi = EROFS_SB(sb);
> +	char *name;
> +	char *str = NULL;
>  	int err;
>  
> +	if (erofs_is_fscache_mode(sb)) {
> +		if (sbi->opt.domain_id) {
> +			str = kasprintf(GFP_KERNEL, "%s,%s", sbi->opt.domain_id,
> +					sbi->opt.fsid);
> +			if (!str)
> +				return -ENOMEM;
> +			name = str;
> +		} else {
> +			name = sbi->opt.fsid;
> +		}
> +	} else {
> +		name = sb->s_id;
> +	}
>  	sbi->s_kobj.kset = &erofs_root;
>  	init_completion(&sbi->s_kobj_unregister);
> -	err = kobject_init_and_add(&sbi->s_kobj, &erofs_sb_ktype, NULL, "%s",
> -			erofs_is_fscache_mode(sb) ? sbi->opt.fsid : sb->s_id);
> +	err = kobject_init_and_add(&sbi->s_kobj, &erofs_sb_ktype, NULL, "%s", name);
> +	kfree(str);
>  	if (err)
>  		goto put_sb_kobj;
>  	return 0;

-- 
Thanks,
Jingbo