linux-kernel - Re: [PATCH v3 0/3+1] fanotify accounting for fs/splice.c

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Message-ID: <20230628103821.dnrbnext26ojviyz@quack3>
Date:   Wed, 28 Jun 2023 12:38:21 +0200
From:   Jan Kara <jack@...e.cz>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Ahelenia Ziemiańska 
        <nabijaczleweli@...ijaczleweli.xyz>,
        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>,
        Chung-Chiang Cheng <cccheng@...ology.com>, ltp@...r.kernel.org
Subject: Re: [PATCH v3 0/3+1] fanotify accounting for fs/splice.c

On Tue 27-06-23 21:51:05, Christoph Hellwig wrote:
> Can you please resend this outside this thread?  I really cant't see
> what's new or old here if you have a reply-to in the old thread.
> 
> On Tue, Jun 27, 2023 at 06:55:22PM +0200, Ahelenia Ziemiańska wrote:
> > In 1/3 I've applied if/else if/else tree like you said,
> > and expounded a bit in the message.
> > 
> > This is less pretty now, however, since it turns out that
> > iter_file_splice_write() already marks the out fd as written because it
> > writes to it via vfs_iter_write(), and that sent a double notification.
> 
> It seems like vfs_iter_write is the wrong level to implement
> ->splice_write given that the the ->splice_write caller has already
> checked f_mode, done the equivalent of rw_verify_area and
> should do the fsnotify_modify.  I'd suggest to just open code the
> relevant parts of vfs_iocb_iter_write in iter_file_splice_write.

Yeah, looking into the code I agree (with a small remark that unlike
vfs_iocb_iter_write() this particular variant also needs to work with files
providing only ->write and not ->write_iter). But we can live with
duplicate events for now and this seems like a rather separate cleanup to
do.

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