linux-kernel - Are there u32 atomic bitops? (or dealing w/ i

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Message-ID: <CALCETrXs15M-cJRGD_R7fXBxOXR=Pyqsh2dVC78DgShxwn60nA@mail.gmail.com>
Date:	Mon, 17 Dec 2012 17:10:21 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	linux-kernel@...r.kernel.org,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Are there u32 atomic bitops? (or dealing w/ i_flags)

I want to change inode->i_flags access to be atomic -- there are some
locking oddities right now, I think, and I want to use a new inode
flag to signal mtime updates from page_mkwrite.  The problem is that
i_flags is an unsigned int, and making it an unsigned long seems like
a waste, but there aren't any u32 atomic bitops.

What should I do?  Suck it up and waste four bytes on 64-bit machines?

In general, having atomic flag words be long seems likely to waste
bits on 64-bit architectures.

--Andy
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