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From:   David Howells <dhowells@redhat.com>
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References: <542f749c-b0f1-1de6-cb41-26e296afb2df@linux.alibaba.com> <20220406075612.60298-5-jefflexu@linux.alibaba.com> <20220406075612.60298-1-jefflexu@linux.alibaba.com> <1091405.1649680508@warthog.procyon.org.uk>
To:     JeffleXu <jefflexu@linux.alibaba.com>
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Subject: Re: [PATCH v8 04/20] cachefiles: notify user daemon when withdrawing cookie
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Date:   Mon, 11 Apr 2022 14:42:34 +0100
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JeffleXu <jefflexu@linux.alibaba.com> wrote:

> > 
> >> +	if (fd == 0)
> >> +		return -ENOENT;
> > 
> > 0 is a valid fd.
> 
> Yeah, but IMHO fd 0 is always for stdin? I think the allocated anon_fd
> won't install at fd 0. Please correct me if I'm wrong.

If someone has closed 0, then you'll get 0 next, I'm pretty sure.  Try it and
see.

> In fact I wanna use "fd == 0" as the initial state as struct
> cachefiles_object is allocated with kmem_cache_zalloc().

I would suggest presetting it to something like -2 to avoid confusion.

David