Message-ID: <53323a3d-ca41-4f7d-cf4d-dc54d14f705a@bytedance.com>
Date:   Wed, 8 Feb 2023 16:16:05 +0800
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Subject: Re: [External] [PATCH 2/4] erofs: maintain cookies of share domain in
 self-contained list
To:     Jingbo Xu <jefflexu@linux.alibaba.com>, xiang@kernel.org,
        chao@kernel.org, linux-erofs@lists.ozlabs.org
Cc:     huyue2@coolpad.com, linux-kernel@vger.kernel.org,
        zhujia.zj@bytedance.com
References: <cover.1675840368.git.jefflexu@linux.alibaba.com>
 <99618b85e5802aacf498387b48c61f1307c6f1f7.1675840368.git.jefflexu@linux.alibaba.com>
From:   Jia Zhu <zhujia.zj@bytedance.com>
In-Reply-To: <99618b85e5802aacf498387b48c61f1307c6f1f7.1675840368.git.jefflexu@linux.alibaba.com>
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在 2023/2/8 15:16, Jingbo Xu 写道:
> We'd better not touch sb->s_inodes list and inode->i_count directly.
> Let's maintain cookies of share domain in a self-contained list in erofs.
> 
> Besides, relinquish cookie with the mutext held.  Otherwise if a cookie
                                       ~~~~~~
                                       mutex
Besides this, LGTM.

Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>

> is registered when the old cookie with the same name in the same domain
> has been removed from the list but not relinquished yet, fscache may
> complain "Duplicate cookie detected".
> 
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> ---
>   fs/erofs/fscache.c  | 48 ++++++++++++++++++++++-----------------------
>   fs/erofs/internal.h |  4 ++++
>   2 files changed, 27 insertions(+), 25 deletions(-)
> 
> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> index 03de4dc99302..2f5930e177cc 100644
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@ -7,8 +7,11 @@
>   #include "internal.h"
>   
>   static DEFINE_MUTEX(erofs_domain_list_lock);
> -static DEFINE_MUTEX(erofs_domain_cookies_lock);
>   static LIST_HEAD(erofs_domain_list);
> +
> +static DEFINE_MUTEX(erofs_domain_cookies_lock);
> +static LIST_HEAD(erofs_domain_cookies_list);
> +
>   static struct vfsmount *erofs_pseudo_mnt;
>   
>   struct erofs_fscache_request {
> @@ -318,8 +321,6 @@ const struct address_space_operations erofs_fscache_access_aops = {
>   
>   static void erofs_fscache_domain_put(struct erofs_domain *domain)
>   {
> -	if (!domain)
> -		return;
>   	mutex_lock(&erofs_domain_list_lock);
>   	if (refcount_dec_and_test(&domain->ref)) {
>   		list_del(&domain->list);
> @@ -434,6 +435,8 @@ struct erofs_fscache *erofs_fscache_acquire_cookie(struct super_block *sb,
>   	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
>   	if (!ctx)
>   		return ERR_PTR(-ENOMEM);
> +	INIT_LIST_HEAD(&ctx->node);
> +	refcount_set(&ctx->ref, 1);
>   
>   	cookie = fscache_acquire_cookie(volume, FSCACHE_ADV_WANT_CACHE_SIZE,
>   					name, strlen(name), NULL, 0, 0);
> @@ -479,6 +482,7 @@ static void erofs_fscache_relinquish_cookie(struct erofs_fscache *ctx)
>   	fscache_unuse_cookie(ctx->cookie, NULL, NULL);
>   	fscache_relinquish_cookie(ctx->cookie, false);
>   	iput(ctx->inode);
> +	iput(ctx->anon_inode);
>   	kfree(ctx->name);
>   	kfree(ctx);
>   }
> @@ -511,6 +515,7 @@ struct erofs_fscache *erofs_fscache_domain_init_cookie(struct super_block *sb,
>   
>   	ctx->domain = domain;
>   	ctx->anon_inode = inode;
> +	list_add(&ctx->node, &erofs_domain_cookies_list);
>   	inode->i_private = ctx;
>   	refcount_inc(&domain->ref);
>   	return ctx;
> @@ -524,29 +529,23 @@ struct erofs_fscache *erofs_domain_register_cookie(struct super_block *sb,
>   						   char *name,
>   						   unsigned int flags)
>   {
> -	struct inode *inode;
>   	struct erofs_fscache *ctx;
>   	struct erofs_domain *domain = EROFS_SB(sb)->domain;
> -	struct super_block *psb = erofs_pseudo_mnt->mnt_sb;
>   
>   	mutex_lock(&erofs_domain_cookies_lock);
> -	spin_lock(&psb->s_inode_list_lock);
> -	list_for_each_entry(inode, &psb->s_inodes, i_sb_list) {
> -		ctx = inode->i_private;
> -		if (!ctx || ctx->domain != domain || strcmp(ctx->name, name))
> +	list_for_each_entry(ctx, &erofs_domain_cookies_list, node) {
> +		if (ctx->domain != domain || strcmp(ctx->name, name))
>   			continue;
>   		if (!(flags & EROFS_REG_COOKIE_NEED_NOEXIST)) {
> -			igrab(inode);
> +			refcount_inc(&ctx->ref);
>   		} else {
>   			erofs_err(sb, "%s already exists in domain %s", name,
>   				  domain->domain_id);
>   			ctx = ERR_PTR(-EEXIST);
>   		}
> -		spin_unlock(&psb->s_inode_list_lock);
>   		mutex_unlock(&erofs_domain_cookies_lock);
>   		return ctx;
>   	}
> -	spin_unlock(&psb->s_inode_list_lock);
>   	ctx = erofs_fscache_domain_init_cookie(sb, name, flags);
>   	mutex_unlock(&erofs_domain_cookies_lock);
>   	return ctx;
> @@ -563,23 +562,22 @@ struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,
>   
>   void erofs_fscache_unregister_cookie(struct erofs_fscache *ctx)
>   {
> -	bool drop;
> -	struct erofs_domain *domain;
> +	struct erofs_domain *domain = NULL;
>   
>   	if (!ctx)
>   		return;
> -	domain = ctx->domain;
> -	if (domain) {
> -		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;
> -	}
> +	if (!ctx->domain)
> +		return erofs_fscache_relinquish_cookie(ctx);
>   
> -	erofs_fscache_relinquish_cookie(ctx);
> -	erofs_fscache_domain_put(domain);
> +	mutex_lock(&erofs_domain_cookies_lock);
> +	if (refcount_dec_and_test(&ctx->ref)) {
> +		domain = ctx->domain;
> +		list_del(&ctx->node);
> +		erofs_fscache_relinquish_cookie(ctx);
> +	}
> +	mutex_unlock(&erofs_domain_cookies_lock);
> +	if (domain)
> +		erofs_fscache_domain_put(domain);
>   }
>   
>   int erofs_fscache_register_fs(struct super_block *sb)
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 48a2f33de15a..8358cf5f731e 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -109,7 +109,11 @@ struct erofs_fscache {
>   	struct fscache_cookie *cookie;
>   	struct inode *inode;
>   	struct inode *anon_inode;
> +
> +	/* used for share domain mode */
>   	struct erofs_domain *domain;
> +	struct list_head node;
> +	refcount_t ref;
>   	char *name;
>   };
>