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

[Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>]

On Wed, Sep 14, 2022 at 06:50:41PM +0800, 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@xxxxxxxxxxxxx>
> ---
>  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);
>  	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;

	struct erofs_domain *domain = EROFS_SB(sb)->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);
> +
> +	inode = new_inode(erofs_pseudo_mnt->mnt_sb);
> +	if (!inode) {
> +		kfree(ctx->name);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	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 erofs_domain *domain = EROFS_SB(sb)->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;
> +		}

		if (!ctx || ctx->domain != domain ||
		    strcmp(ctx->name, name))
			continue;
		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);

	if (EROFS_SB(sb)->opt.domain_id)
		return erofs_domain_register_cookie(sb, name, need_inode);
	Return erofs_fscache_acquire_cookie(sb, name, need_inode);

Thanks,
Gao Xiang