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Date:   Mon, 28 Mar 2022 10:42:42 +0800
From:   Gao Xiang <hsiangkao@linux.alibaba.com>
To:     Jeffle Xu <jefflexu@linux.alibaba.com>
Cc:     dhowells@redhat.com, linux-cachefs@redhat.com, xiang@kernel.org,
        chao@kernel.org, linux-erofs@lists.ozlabs.org,
        torvalds@linux-foundation.org, gregkh@linuxfoundation.org,
        willy@infradead.org, linux-fsdevel@vger.kernel.org,
        joseph.qi@linux.alibaba.com, bo.liu@linux.alibaba.com,
        tao.peng@linux.alibaba.com, gerry@linux.alibaba.com,
        eguan@linux.alibaba.com, linux-kernel@vger.kernel.org,
        luodaowen.backend@bytedance.com, tianzichen@kuaishou.com,
        fannaihao@baidu.com
Subject: Re: [PATCH v6 10/22] erofs: add mode checking helper
Message-ID: <YkEgoqAKNTf45lJa@B-P7TQMD6M-0146.local>
Mail-Followup-To: Jeffle Xu <jefflexu@linux.alibaba.com>,
        dhowells@redhat.com, linux-cachefs@redhat.com, xiang@kernel.org,
        chao@kernel.org, linux-erofs@lists.ozlabs.org,
        torvalds@linux-foundation.org, gregkh@linuxfoundation.org,
        willy@infradead.org, linux-fsdevel@vger.kernel.org,
        joseph.qi@linux.alibaba.com, bo.liu@linux.alibaba.com,
        tao.peng@linux.alibaba.com, gerry@linux.alibaba.com,
        eguan@linux.alibaba.com, linux-kernel@vger.kernel.org,
        luodaowen.backend@bytedance.com, tianzichen@kuaishou.com,
        fannaihao@baidu.com
References: <20220325122223.102958-1-jefflexu@linux.alibaba.com>
 <20220325122223.102958-11-jefflexu@linux.alibaba.com>
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On Fri, Mar 25, 2022 at 08:22:11PM +0800, Jeffle Xu wrote:
> Until then erofs is exactly blockdev based filesystem. In other using
> scenarios (e.g. container image), erofs needs to run upon files.
> 
> This patch set is going to introduces a new nodev mode, in which erofs
> could be mounted from a bootstrap blob file containing complete erofs
> image.
> 
> Add a helper checking which mode erofs works in.
> 
> Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
> ---
>  fs/erofs/internal.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index e424293f47a2..1486e2573667 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -161,6 +161,11 @@ struct erofs_sb_info {
>  #define set_opt(opt, option)	((opt)->mount_opt |= EROFS_MOUNT_##option)
>  #define test_opt(opt, option)	((opt)->mount_opt & EROFS_MOUNT_##option)
>  
> +static inline bool erofs_is_nodev_mode(struct super_block *sb)

I've seen a lot of such

+		if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) &&
+		    erofs_is_nodev_mode(sb)) {

usages in the followup patches, which makes me wonder if the configuration
can be checked in the helper as well. Also maybe rename it as
erofs_is_fscache_mode()?

Thanks,
Gao Xiang

> +{
> +	return !sb->s_bdev;
> +}
> +
>  enum {
>  	EROFS_ZIP_CACHE_DISABLED,
>  	EROFS_ZIP_CACHE_READAHEAD,
> -- 
> 2.27.0