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From: Tao Lyu <tao.lyu@epfl.ch>
To: "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Question about O_APPEND | O_DIRECT
Thread-Topic: Question about O_APPEND | O_DIRECT
Thread-Index: AQHaHjflhODFfyeMXUSkxSGiPt/2HA==
Date: Thu, 23 Nov 2023 18:14:51 +0000
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Hi,

Sorry to bother you here.

I'm using NFS and realize it doesn't support opening a file with "O_DIRECT =
| O_APPEND".

After checking the source code,=20
I found it has one function that checks explicitly whether there is a combi=
nation flag of "O_APPEND | O_DIRECT".
If so, it will return invalid arguments.

int nfs_check_flags(int flags)
{
=A0=A0=A0 if ((flags & (O_APPEND | O_DIRECT)) =3D=3D (O_APPEND | O_DIRECT))
=A0=A0=A0=A0=A0=A0=A0 return -EINVAL;

=A0=A0=A0 return 0;
}

But I don't understand why NFS doesn't support this flag combination.
I'd appreciate it if someone could explain this to me.

Thanks in advance.

Best,
Tao