linux-kernel - Re: splice(-> FIFO) never wakes up inotify IN

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Message-ID: <20230626135159.wzbtjgo6qryfet4e@quack3>
Date:   Mon, 26 Jun 2023 15:51:59 +0200
From:   Jan Kara <jack@...e.cz>
To:     Ahelenia Ziemiańska 
        <nabijaczleweli@...ijaczleweli.xyz>
Cc:     Amir Goldstein <amir73il@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jan Kara <jack@...e.cz>
Subject: Re: splice(-> FIFO) never wakes up inotify IN_MODIFY?

On Mon 26-06-23 14:57:55, Ahelenia Ziemiańska wrote:
> On Mon, Jun 26, 2023 at 02:19:42PM +0200, Ahelenia Ziemiańska wrote:
> > > splice(2) differentiates three different cases:
> > >         if (ipipe && opipe) {
> > > ...
> > >         if (ipipe) {
> > > ...
> > >         if (opipe) {
> > > ...
> > > 
> > > IN_ACCESS will only be generated for non-pipe input
> > > IN_MODIFY will only be generated for non-pipe output
> > >
> > > Similarly FAN_ACCESS_PERM fanotify permission events
> > > will only be generated for non-pipe input.
> Sorry, I must've misunderstood this as "splicing to a pipe generates
> *ACCESS". Testing reveals this is not the case. So is it really true
> that the only way to poll a pipe is a sleep()/read(O_NONBLOCK) loop?

So why doesn't poll(3) work? AFAIK it should...

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR