erofs: protect s_inodes with s_inode_list_lock for fscache

s_inodes is superblock-specific resource, which should be
protected by sb's specific lock s_inode_list_lock.

Link: https://lore.kernel.org/r/TYCP286MB23238380DE3B74874E8D78ABCA299@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM
Fixes: 7d419637 ("erofs: Support sharing cookies in the same domain")
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Dawei Li <set_pte_at@outlook.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

fs/erofs/fscache.c

@@ -590,14 +590,17 @@ struct erofs_fscache *erofs_domain_register_cookie(struct super_block *sb,
 	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))
 			continue;
 		igrab(inode);
+		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, need_inode);
 	mutex_unlock(&erofs_domain_cookies_lock);
 	return ctx;