linux-kernel - Re: [PATCH] tmpfs: preserve SB_I

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Message-ID: <0a5c4b7deb443ac5f62d00b0bd0e1dd649bef8fe.camel@kernel.org>
Date: Tue, 19 Aug 2025 06:08:47 -0400
From: Jeff Layton <jlayton@...nel.org>
To: libaokun@...weicloud.com, linux-mm@...ck.org
Cc: hughd@...gle.com, baolin.wang@...ux.alibaba.com,
 akpm@...ux-foundation.org, 	linux-kernel@...r.kernel.org, Baokun Li
 <libaokun1@...wei.com>
Subject: Re: [PATCH] tmpfs: preserve SB_I_VERSION on remount

On Tue, 2025-08-19 at 14:18 +0800, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> Now tmpfs enables i_version by default and tmpfs does not modify it. But
> SB_I_VERSION can also be modified via sb_flags, and reconfigure_super()
> always overwrites the existing flags with the latest ones. This means that
> if tmpfs is remounted without specifying iversion, the default i_version
> will be unexpectedly disabled.
> 
> To ensure iversion remains enabled, SB_I_VERSION is now always set for
> fc->sb_flags in shmem_init_fs_context(), instead of for sb->s_flags in
> shmem_fill_super().
> 
> Fixes: 36f05cab0a2c ("tmpfs: add support for an i_version counter")
> Signed-off-by: Baokun Li <libaokun1@...wei.com>
> ---
>  mm/shmem.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index e2c76a30802b..eebe12ff5bc6 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -5081,7 +5081,7 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
>  		sb->s_flags |= SB_NOUSER;
>  	}
>  	sb->s_export_op = &shmem_export_ops;
> -	sb->s_flags |= SB_NOSEC | SB_I_VERSION;
> +	sb->s_flags |= SB_NOSEC;
>  
>  #if IS_ENABLED(CONFIG_UNICODE)
>  	if (!ctx->encoding && ctx->strict_encoding) {
> @@ -5385,6 +5385,9 @@ int shmem_init_fs_context(struct fs_context *fc)
>  
>  	fc->fs_private = ctx;
>  	fc->ops = &shmem_fs_context_ops;
> +#ifdef CONFIG_TMPFS
> +	fc->sb_flags |= SB_I_VERSION;
> +#endif
>  	return 0;
>  }
>  

Reviewed-by: Jeff Layton <jlayton@...nel.org>