Re: [RESEND] [PATCH] lseek: remove i_mutex

[Andrew Morton]

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