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Date: 3 Mar 2014 16:03:59 -0500
From: "George Spelvin" <linux@...izon.com>
To: torvalds@...ux-foundation.org
Cc: linux@...izon.com, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, viro@...IV.linux.org.uk
Subject: Re: Update of file offset on write() etc. is non-atomic with I/O
> struct fd {
> struct file *file;
> - int need_put;
> + unsigned need_put:1, need_pos_unlock:1;
> };
Since we're rounding up to 2*sizeof(struct file *) anyway, is this a case
where wasting space on a couple of char (or bool) flags would generate
better code than a bitfield?
In particular, the code to set need_pos_unlock (which will be executed
each read/write for most files) is messy in the bitfield case.
A byte store is much cleaner.
(If you want to use bits, why not use the two lsbits of the file pointer
for the purpose? That would save a lot of space.)
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