linux-ext4 - Re: [PATCH] ext4: check for a good block group before loading buddy pages

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Message-ID: <20100521031023.GC11651@thunk.org>
Date:	Thu, 20 May 2010 23:10:23 -0400
From:	tytso@....edu
To:	Curt Wohlgemuth <curtw@...gle.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: check for a good block group before loading
 buddy pages

On Fri, May 07, 2010 at 09:00:16AM -0700, Curt Wohlgemuth wrote:
> This adds a new field in ext4_group_info to cache the largest available
> block range in a block group; and don't load the buddy pages until *after*
> we've done a sanity check on the block group.
> 
> With large allocation requests (e.g., fallocate(), 8MiB) and relatively full
> partitions, it's easy to have no block groups with a block extent large
> enough to satisfy the input request length.  This currently causes the loop
> during cr == 0 in ext4_mb_regular_allocator() to load the buddy bitmap pages
> for EVERY block group.  That can be a lot of pages.  The patch below allows
> us to call ext4_mb_good_group() BEFORE we load the buddy pages.
> 
>Signed-off-by: Curt Wohlgemuth <curtw@...gle.com>

Added to the ext4 patch queue.

					- Ted
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