Re: [EXT4 set 4][PATCH 1/5] i_version:64 bit inode version

From: Andrew Morton
Date: Wed Jul 11 2007 - 01:22:39 EST


On Wed, 11 Jul 2007 15:05:27 +1000 Neil Brown <neilb@xxxxxxx> wrote:

>
> It just occurred to me:
>
> If i_version is 64bit, then knfsd would need to be careful when
> reading it on a 32bit host. What are the locking rules?
>
> Presumably it is only updated under i_mutex protection, but having to
> get i_mutex to read it would seem a little heavy handed.
>
> Should it use a seqlock like i_size?
> Could we use the same seqlock that i_size uses, or would we need a
> separate one?
>

seqlocks are a bit of a pain to use (we've had plenty of deadlocks on the
i_size one). We could reuse inode.i_lock for this modification. Its
mandate is "general purpose innermost lock to protect stuff in this inode".


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