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Message-ID: <8097af66-f39d-e197-5a47-a62e731c598a@bytedance.com>
Date:   Thu, 1 Sep 2022 11:45:01 +0800
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Subject: Re: [External] Re: [RFC PATCH 1/5] erofs: add 'domain_id' mount
 option for on-demand read sementics
To:     linux-erofs@lists.ozlabs.org, xiang@kernel.org, chao@kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        yinxin.x@bytedance.com, jefflexu@linux.alibaba.com,
        huyue2@coolpad.com
References: <20220831123125.68693-1-zhujia.zj@bytedance.com>
 <20220831123125.68693-2-zhujia.zj@bytedance.com>
 <YxAnqC8pYf75epr1@B-P7TQMD6M-0146.local>
From:   Jia Zhu <zhujia.zj@bytedance.com>
In-Reply-To: <YxAnqC8pYf75epr1@B-P7TQMD6M-0146.local>
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在 2022/9/1 11:31, Gao Xiang 写道:
> On Wed, Aug 31, 2022 at 08:31:21PM +0800, 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@bytedance.com>
>> ---
>>   fs/erofs/internal.h |  1 +
>>   fs/erofs/super.c    | 17 +++++++++++++++++
>>   2 files changed, 18 insertions(+)
>>
>> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
>> index cfee49d33b95..fe435d077f1a 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;
>>   };
>>   
>>   struct erofs_dev_context {
>> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
>> index 3173debeaa5a..fb5a84a07bd5 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:
>> +		kfree(ctx->opt.domain_id);
>> +		ctx->opt.domain_id = kstrdup(param->string, GFP_KERNEL);
>> +		if (!ctx->opt.domain_id)
>> +			return -ENOMEM;
>> +#ifdef CONFIG_EROFS_FS_ONDEMAND
>> +#else
>> +		errorfc(fc, "domain_id option not supported");
> 
> Just one question, why not write as below?
> 
> #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
> 
> Thanks,
> Gao Xiang
> 
Thanks for catching this. Maybe something went wrong when I split the
patch. I'll fix it in next version.

Thanks,
Zhu Jia
>>   #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;
>>   
>> @@ -838,6 +851,7 @@ 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);
>>   }
>>   
>> @@ -892,6 +906,7 @@ static void erofs_kill_sb(struct super_block *sb)
>>   	erofs_fscache_unregister_cookie(&sbi->s_fscache);
>>   	erofs_fscache_unregister_fs(sb);
>>   	kfree(sbi->opt.fsid);
>> +	kfree(sbi->opt.domain_id);
>>   	kfree(sbi);
>>   	sb->s_fs_info = NULL;
>>   }
>> @@ -1044,6 +1059,8 @@ 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;
>>   }
>> -- 
>> 2.20.1