linux-kernel - Re: [PATCH] vfs: make open_with_fake_path() not contribute to nr

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Message-ID: <18289.1531987758@warthog.procyon.org.uk>
Date:   Thu, 19 Jul 2018 09:09:18 +0100
From:   David Howells <dhowells@...hat.com>
To:     Miklos Szeredi <mszeredi@...hat.com>
Cc:     dhowells@...hat.com, Al Viro <viro@...iv.linux.org.uk>,
        linux-unionfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] vfs: make open_with_fake_path() not contribute to nr_files

Miklos Szeredi <mszeredi@...hat.com> wrote:

> Stacking file operations in overlay will store an extra open file for each
> overlay file opened.
> 
> The overhead is just that of "struct file" which is about 256bytes, because
> overlay already pins an extra dentry and inode when the file is open, which
> add up to a much larger overhead.
> 
> For fear of breaking working setups, don't start accounting the extra file.

Sounds useful for cachefiles too, though Christoph Hellwig objected strongly
last time I tried this, so you might want to check with him directly.

David