[External] Re: [PATCH V3 6/6] erofs: Support sharing cookies in the same domain

[Jia Zhu]

在 2022/9/15 14:53, JeffleXu 写道:
> 
> 
> On 9/14/22 6:50 PM, Jia Zhu wrote:
>> Several erofs filesystems can belong to one domain, and data blobs can
>> be shared among these erofs filesystems of same domain.
>>
>> Users could specify domain_id mount option to create or join into a
>> domain.
>>
>> Signed-off-by: Jia Zhu <zhujia.zj at bytedance.com>
>> ---
>>   fs/erofs/fscache.c  | 89 +++++++++++++++++++++++++++++++++++++++++++--
>>   fs/erofs/internal.h |  4 +-
>>   2 files changed, 89 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
>> index 4e0a441afb7d..e9ae1ee963e2 100644
>> --- a/fs/erofs/fscache.c
>> +++ b/fs/erofs/fscache.c
>> @@ -7,6 +7,7 @@
>>   #include "internal.h"
>>   
>>   static DEFINE_MUTEX(erofs_domain_list_lock);
>> +static DEFINE_MUTEX(erofs_domain_cookies_lock);
>>   static LIST_HEAD(erofs_domain_list);
>>   static struct vfsmount *erofs_pseudo_mnt;
>>   
>> @@ -504,7 +505,6 @@ static int erofs_fscache_init_domain(struct super_block *sb)
>>   
>>   	domain->volume = sbi->volume;
>>   	refcount_set(&domain->ref, 1);
>> -	mutex_init(&domain->mutex);
> 
> This needs to be folded into patch 4.
Thanks.
> 
> 
>>   	list_add(&domain->list, &erofs_domain_list);
>>   	return 0;
>>   out:
>> @@ -534,8 +534,8 @@ static int erofs_fscache_register_domain(struct super_block *sb)
>>   	return err;
>>   }
>>   
>> -struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,
>> -						     char *name, bool need_inode)
>> +struct erofs_fscache *erofs_fscache_acquire_cookie(struct super_block *sb,
>> +						    char *name, bool need_inode)
>>   {
>>   	struct fscache_volume *volume = EROFS_SB(sb)->volume;
>>   	struct erofs_fscache *ctx;
>> @@ -585,13 +585,96 @@ struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,
>>   	return ERR_PTR(ret);
>>   }
>>   
>> +static
>> +struct erofs_fscache *erofs_fscache_domain_init_cookie(struct super_block *sb,
>> +							char *name, bool need_inode)
>> +{
>> +	struct inode *inode;
>> +	struct erofs_fscache *ctx;
>> +	struct erofs_sb_info *sbi = EROFS_SB(sb);
>> +	struct erofs_domain *domain = sbi->domain;
>> +
>> +	ctx = erofs_fscache_acquire_cookie(sb, name, need_inode);
>> +	if (IS_ERR(ctx))
>> +		return ctx;
>> +
>> +	ctx->name = kstrdup(name, GFP_KERNEL);
>> +	if (!ctx->name)
>> +		return ERR_PTR(-ENOMEM);
> 
> The previously registered erofs_fscache needs to be cleaned up in the
> error path.
Thanks for catching this. I'll fix it in next version.
> 
>> +
>> +	inode = new_inode(erofs_pseudo_mnt->mnt_sb);
>> +	if (!inode) {
>> +		kfree(ctx->name);
>> +		return ERR_PTR(-ENOMEM);
>> +	}
> 
> Ditto.
> 
>> +
>> +	ctx->domain = domain;
>> +	ctx->anon_inode = inode;
>> +	inode->i_private = ctx;
>> +	erofs_fscache_domain_get(domain);
>> +	return ctx;
>> +}
>> +
>> +static
>> +struct erofs_fscache *erofs_domain_register_cookie(struct super_block *sb,
>> +						    char *name, bool need_inode)
>> +{
>> +	struct inode *inode;
>> +	struct erofs_fscache *ctx;
>> +	struct erofs_sb_info *sbi = EROFS_SB(sb);
>> +	struct erofs_domain *domain = sbi->domain;
>> +	struct super_block *psb = erofs_pseudo_mnt->mnt_sb;
>> +
>> +	mutex_lock(&erofs_domain_cookies_lock);
>> +	list_for_each_entry(inode, &psb->s_inodes, i_sb_list) {
>> +		ctx = inode->i_private;
>> +		if (!ctx)
>> +			continue;
>> +		if (ctx->domain == domain && !strcmp(ctx->name, name)) {
>> +			igrab(inode);
>> +			mutex_unlock(&erofs_domain_cookies_lock);
>> +			return ctx;
>> +		}
>> +	}
>> +	ctx = erofs_fscache_domain_init_cookie(sb, name, need_inode);
>> +	mutex_unlock(&erofs_domain_cookies_lock);
>> +	return ctx;
>> +}
>> +
>> +struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,
>> +						     char *name, bool need_inode)
>> +{
>> +	struct erofs_sb_info *sbi = EROFS_SB(sb);
>> +
>> +	if (sbi->opt.domain_id)
>> +		return erofs_domain_register_cookie(sb, name, need_inode);
>> +	else
>> +		return erofs_fscache_acquire_cookie(sb, name, need_inode);
>> +}
>> +
>>   void erofs_fscache_unregister_cookie(struct erofs_fscache *ctx)
>>   {
>> +	struct erofs_domain *domain;
>> +
>>   	if (!ctx)
>>   		return;
>> +	domain = ctx->domain;
>> +	if (domain) {
>> +		mutex_lock(&erofs_domain_cookies_lock);
>> +		/* Cookie is still in use */
>> +		if (atomic_read(&ctx->anon_inode->i_count) > 1) {
>> +			iput(ctx->anon_inode);
>> +			mutex_unlock(&erofs_domain_cookies_lock);
>> +			return;
>> +		}
>> +		iput(ctx->anon_inode);
>> +		kfree(ctx->name);
>> +		mutex_unlock(&erofs_domain_cookies_lock);
> 
> 		mutex_lock(&erofs_domain_cookies_lock);
> 		drop = atomic_read(&ctx->anon_inode->i_count) == 1;
> 		iput(ctx->anon_inode);
> 		mutex_unlock(&erofs_domain_cookies_lock);
> 
> 		if (!drop)
> 			return;
This code style is more intuitive, I'll revise it, thanks.
>> +	}
>>   >  	fscache_unuse_cookie(ctx->cookie, NULL, NULL);
>>   	fscache_relinquish_cookie(ctx->cookie, false);
>> +	erofs_fscache_domain_put(domain);
>>   	ctx->cookie = NULL;
> 
> 	fscache_unuse_cookie(ctx->cookie, NULL, NULL);
> 	fscache_relinquish_cookie(ctx->cookie, false);
> 	erofs_fscache_domain_put(domain);
> 	kfree(ctx->name);
> 
>>   
>>   	iput(ctx->inode);
>> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
>> index 4dd0b545755a..8a6f94b27a23 100644
>> --- a/fs/erofs/internal.h
>> +++ b/fs/erofs/internal.h
>> @@ -101,7 +101,6 @@ struct erofs_sb_lz4_info {
>>   
>>   struct erofs_domain {
>>   	refcount_t ref;
>> -	struct mutex mutex;
>>   	struct list_head list;
>>   	struct fscache_volume *volume;
>>   	char *domain_id;
>> @@ -110,6 +109,9 @@ struct erofs_domain {
>>   struct erofs_fscache {
>>   	struct fscache_cookie *cookie;
>>   	struct inode *inode;
>> +	struct inode *anon_inode;
>> +	struct erofs_domain *domain;
>> +	char *name;
>>   };
>>   
>>   struct erofs_sb_info {
>