linux-kernel - Re: [PATCH] nfs: pass flags to second superblock

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Message-ID: <CAFX2Jfk=FUNYecYT15_FQSKv6ajcWuM-724hUeryTJc7auhCHg@mail.gmail.com>
Date: Mon, 25 Nov 2024 17:34:39 -0500
From: Anna Schumaker <anna@...nel.org>
To: Li Lingfeng <lilingfeng3@...wei.com>
Cc: trondmy@...nel.org, trond.myklebust@...merspace.com, jlayton@...nel.org, 
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
	yukuai1@...weicloud.com, houtao1@...wei.com, yi.zhang@...wei.com, 
	yangerkun@...wei.com, lilingfeng@...weicloud.com
Subject: Re: [PATCH] nfs: pass flags to second superblock

Hi Li,

On Wed, Nov 13, 2024 at 11:33 PM Li Lingfeng <lilingfeng3@...wei.com> wrote:
>
> During the process of mounting an NFSv4 client, two superblocks will be
> created in sequence. The first superblock corresponds to the root
> directory exported by the server, and the second superblock corresponds to
> the directory that will be actually mounted. The first superblock will
> eventually be destroyed.
> The flag passed from user mode will only be passed to the first
> superblock, resulting in the actual used superblock not carrying the flag
> passed from user mode(fs_context_for_submount() will set sb_flags as 0).
>
> Since the superblock of NFS does not carry the ro tag, the file system
> status displayed by /proc/self/mountstats shows that NFS is always in the
> rw state, which may mislead users.
>
> Pass sb_flags of the fc which carry flags passed by user to second
> superblock to fix it.
>
> Fixes: 281cad46b34d ("NFS: Create a submount rpc_op")
> Signed-off-by: Li Lingfeng <lilingfeng3@...wei.com>
> ---
>  fs/nfs/nfs4super.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/fs/nfs/nfs4super.c b/fs/nfs/nfs4super.c
> index b29a26923ce0..9a3b73a33fbf 100644
> --- a/fs/nfs/nfs4super.c
> +++ b/fs/nfs/nfs4super.c
> @@ -233,6 +233,7 @@ static int do_nfs4_mount(struct nfs_server *server,
>         if (IS_ERR(dentry))
>                 return PTR_ERR(dentry);
>
> +       dentry->d_sb->s_flags = fc->sb_flags;

I'm seeing a handful of new xfstests failures that I bisected to this
patch: generic/157, generic/184, generic/306, generic/564, and
generic/598.

I'm seeing this on NFS v4.1 and v4.2, and it looks like each one of
these failures is due to a new -EIO error being generated. Any
thoughts about what could be causing this?

Thanks,
Anna


>         fc->root = dentry;
>         return 0;
>  }
> --
> 2.31.1
>