linux-kernel - Re: [RESEND] [PATCH] lseek: remove i

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Message-Id: <20090205120519.a62e8c4f.akpm@linux-foundation.org>
Date:	Thu, 5 Feb 2009 12:05:19 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RESEND] [PATCH] lseek: remove i_mutex

On Tue, 03 Feb 2009 17:04:40 +0900
Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp> wrote:

> I removed i_mutex from generic_file_llseek.
> I think that the reason of protecting lseek with i_mutex is just
> touching i_size atomically.
> 
> So I introduce i_size_read here so i_mutex is no longer needed.
> 
> Following patch removes i_mutex from generic_file_llseek, and deletes 
> generic_file_llseek_nolock totally.
> 
> Currently there is i_mutex contention not only around lseek, but also fsync or write.
> So,  I think we can mitigate i_mutex contention between fsync lseek and write by
> removing i_mutex.

Prior to this change, generic_file_llseek() modified file->f_pos
atomically with respect to other i_mutex holders.

After this change, it doesn't.
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