linux-kernel - Re: [PATCH] tmpfs: use ida to get inode number

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Message-ID: <20191120154552.GS20752@bombadil.infradead.org>
Date:   Wed, 20 Nov 2019 07:45:52 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     zhengbin <zhengbin13@...wei.com>
Cc:     viro@...iv.linux.org.uk, hughd@...gle.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, houtao1@...wei.com,
        yi.zhang@...wei.com
Subject: Re: [PATCH] tmpfs: use ida to get inode number

On Wed, Nov 20, 2019 at 10:23:18PM +0800, zhengbin wrote:
> I have tried to change last_ino type to unsigned long, while this was
> rejected, see details on https://patchwork.kernel.org/patch/11023915.

Did you end up trying sbitmap?

What I think is fundamentally wrong with this patch is that you've found a
problem in get_next_ino() and decided to use a different scheme for this
one filesystem, leaving every other filesystem which uses get_next_ino()
facing the same problem.

That could be acceptable if you explained why tmpfs is fundamentally
different from all the other filesystems that use get_next_ino(), but
you haven't (and I don't think there is such a difference.  eg pipes,
autofs and ipc mqueue could all have the same problem.

There are some other problems I noticed, but they're not worth bringing
up until this fundamental design choice is justified.