linux-ext4 - Re: [PATCH RESEND] ext4: Fix kernel BUG at fs/ext4/mballoc.c:910!

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Date:	Thu, 14 Feb 2008 15:33:39 -0800
From:	Mingming Cao <cmm@...ibm.com>
To:	Andreas Dilger <adilger@....com>
Cc:	Valerie Clement <valerie.clement@...l.net>,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: [PATCH RESEND] ext4: Fix kernel BUG at fs/ext4/mballoc.c:910!

On Thu, 2008-02-14 at 15:13 -0700, Andreas Dilger wrote:
> On Feb 14, 2008  17:35 +0100, Valerie Clement wrote:
> > From: Valerie Clement <valerie.clement@...l.net>
> > 
> > With the flex_bg feature enabled, a large file creation oopses the
> > kernel.
> > The BUG_ON is:
> > 	BUG_ON(len >= EXT4_BLOCKS_PER_GROUP(sb));
> > 
> > As the allocation of the bitmaps and the inode table can be done
> > outside the block group with flex_bg, this allows to allocate up to
> > EXT4_BLOCKS_PER_GROUP blocks in a group.
> > Depending on the group size and the block size, extents might be 
> > larger than BLOCKS_PER_GROUP(); use EXT_INIT_MAX_LEN instead of 
> > BLOCKS_PER_GROUP().
> 
> In fact, my earlier review of this patch was incorrect, and Aneesh pointed
> out the correct answer.  The ext4_mb_mark_free_simple() function is only
> called from ext4_mb_generate_buddy() to generate the buddy bitmap from the
> on-disk block bitmap, and in that case the @len parameter should always
> be <= EXT4_BLOCKS_PER_GROUP().  I think the original patch was correct.
> 
> Sorry about the confusion.  I thought at first glance this was for
> freeing the blocks from releasing an extent, but that is incorrect.
> 
Ok, I added the revised first patch
http://repo.or.cz/w/ext4-patch-queue.git?a=blob;f=ext4_fix_BUGON_at_mballoc.patch;h=c2d11bd2ec46c8103d4fad7c62cd792b7daec202;hb=067598f1a058a05342afee9720a0538b871c61f4

Mingming
> Cheers, Andreas
> --
> Andreas Dilger
> Sr. Staff Engineer, Lustre Group
> Sun Microsystems of Canada, Inc.
> 

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