linux-kernel - Re: [GIT PULL] 9p update for 5.7

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Message-ID: <20200406164641.GF21484@bombadil.infradead.org>
Date:   Mon, 6 Apr 2020 09:46:41 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Dominique Martinet <asmadeus@...ewreck.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        v9fs-developer@...ts.sourceforge.net,
        Sergey Alirzaev <l29ah@...k.li>
Subject: Re: [GIT PULL] 9p update for 5.7

On Mon, Apr 06, 2020 at 06:40:57PM +0200, Dominique Martinet wrote:
> Anyway, I agree looking at O_NONBLOCK for that isn't obvious.
> I agree with the usecase here and posix allows short reads regardless of
> the flag so the behaviour is legal either way ; the filesystem is
> allowed to return whenever it wants on a whim - let's just add some docs
> as you suggest unless Sergey has something to add.

Ahahahahhahahahahaha.

POSIX may well "allow" short reads, but userspace programmers basically
never check the return value from read().  Short reads aren't actually
allowed.  That's why signals are only allowed to interrupt syscalls if
they're fatal (and the application will never see the returned value
because it's already dead).