From: Ted Ts'o <tytso@mit.edu>
Subject: Re: [PATCH 0/5] mballoc: trivial code cleanup
Date: Mon, 7 Feb 2011 12:41:25 -0500
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	Alex Tomas <alex@clusterfs.com>,
	Theodore Tso <tytso@google.com>
To: Amir Goldstein <amir73il@gmail.com>
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On Sun, Feb 06, 2011 at 10:43:58AM +0200, Amir Goldstein wrote:
> When looking at alloc_sem, I realized that it is only needed to avoid
> race with adjacent group buddy initialization.

Actually, alloc_sem is used to protect all of the block group specific
data structures; the buddy bitmap counters, adjusting the buddy bitmap
itself, the largest free order in a block group, etc.  So even in the
case where block_size == page_size, alloc_sem is still needed!

     	   	      	 	    	      	 - Ted