linux-ext4 - Re: [RFC][PATCH 1/7]ext4: Add EXT4_IOC_ADD_GLOBAL_ALLOC

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Date:	Wed, 24 Jun 2009 02:11:58 +0200
From:	Andreas Dilger <adilger@....com>
To:	Greg Freemyer <greg.freemyer@...il.com>
Cc:	Akira Fujita <a-fujita@...jp.nec.com>, linux-ext4@...r.kernel.org,
	"Theodore Ts'o" <tytso@....edu>, linux-fsdevel@...r.kernel.org
Subject: Re: [RFC][PATCH 1/7]ext4: Add EXT4_IOC_ADD_GLOBAL_ALLOC_RULE	restricts
 block allocation

On Jun 23, 2009  20:02 -0400, Greg Freemyer wrote:
> On Tue, Jun 23, 2009 at 7:19 PM, Andreas Dilger<adilger@....com> wrote:
> > On Jun 23, 2009  17:25 +0900, Akira Fujita wrote:
> >> alloc_flag of ext4_alloc_rule structure is set as "mandatory" or "advisory".
> >> Restricted blocks with "mandatory" are never used by block allocator.
> >> But in "advisory" case, block allocator is allowed to use restricted blocks
> >> when there are no free blocks on FS.
> >
> > Would it make more sense to implement the range protections via the
> > existing preallocation ranges (PA)?  An inode can have multiple
> > PAs attached to it to have it prefer allocations from that range.
> >
> > We could also attach PAs to the superblock to prevent other files from
> > allocating out of those ranges.  This would work better with the existing
> > allocation code instead of creating a second similar mechanism.
> 
> Where can I find documentation about how PA works?  Or is it just in
> the source?  If so, what are one or two calls that cause the PA ranges
> to be set, etc.

Aneesh is the expert on the preallocation code.

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

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