linux-ext4 - Re: [PATCH 1/2] ext4: introduce new i_write

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Message-ID: <20140529162810.GG25041@thunk.org>
Date:	Thu, 29 May 2014 12:28:10 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Lukáš Czerner <lczerner@...hat.com>
Cc:	Namjae Jeon <namjae.jeon@...sung.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	Ashish Sangwan <a.sangwan@...sung.com>
Subject: Re: [PATCH 1/2] ext4: introduce new i_write_mutex to protect
 fallocate

On Thu, May 29, 2014 at 02:42:04PM +0200, Lukáš Czerner wrote:
> 
> I wonder what is the performance impact of this change ? Especially
> since we're not longer taking the lock only in unaligned aio/dio
> case but in all cases ?

Thinking about this some more, this is also going to break parallel
writes, which would be unfortunate.  We might want to change this to
using a rw mutex, where writes take a shared lock, and require
fallocate to take an exclusive lock....

				- Ted
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