linux-ext4 - Re: a question for i_inode's i

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Message-ID: <20080920063502.GB12762@mit.edu>
Date:	Sat, 20 Sep 2008 02:35:02 -0400
From:	Theodore Tso <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	홍신 shin hong <hongshin@...il.com>,
	linux-ext4@...r.kernel.org
Subject: Re: a question for i_inode's i_size in ext2

On Sat, Sep 20, 2008 at 05:25:22AM +0200, Jan Kara wrote:
> Reading i_size is a different matter - see
> i_size_read function. We use seqlock for that - essentially we use an
> atomic counter which is incremented on every change of i_size and check
> that it's value before we started reading i_size and after we have
> finished reading it has not changed. I hope this helps.

Just to clarify for Shin Hong's benefit: this is necessary only on SMP
(or CONFIG_PREEMPT) 32-bit platforms in order to make sure we read a
coherent 64-bit i_size value.

						- Ted
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