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Subject: Re: Weirdness when writing to pseudofs file
To: Konstantin Belousov <kostikbel@gmail.com>
Cc: FreeBSD Current <freebsd-current@freebsd.org>
References: <6ec62e4d-9f93-ffe1-646c-3846c9308334@FreeBSD.org>
 <20190522175133.GC2748@kib.kiev.ua>
From: Johannes Lundberg <johalun@FreeBSD.org>
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Date: Wed, 22 May 2019 10:59:06 -0700
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On 5/22/19 10:51 AM, Konstantin Belousov wrote:
> On Wed, May 22, 2019 at 10:36:34AM -0700, Johannes Lundberg wrote:
>> Hi
>>
>> I'm fiddling with lindebugfs, which is based on pseudofs. When writing
>> to a file,
>>
>> this works: # echo  1 >> /path/to/file
>>
>> but this does not: # echo 1 > /path/to/file
>>
>> "Operation not supported." is returned before the pseudofs code is even
>> entered.
>>
>> Is this expected behavior? (if so, why?)
> Does the file exist ?
>
> Pseudofs does not implement VOP_CREATE(), which is reasonable.

Yes, it exists and my custom write function is receiving the call for
">>". (which is for example used by drm driver debugfs to do certain
things on demand by accepting write to a debugfs file)