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

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Message-ID: <87f94c370906250547l338fd357s2e51291185bc3b2c@mail.gmail.com>
Date:	Thu, 25 Jun 2009 08:47:59 -0400
From:	Greg Freemyer <greg.freemyer@...il.com>
To:	Andreas Dilger <adilger@....com>
Cc:	Akira Fujita <a-fujita@...jp.nec.com>, linux-ext4@...r.kernel.org,
	"Theodore Ts'o" <tytso@....edu>, linux-fsdevel@...r.kernel.org,
	Aneesh Kumar <aneesh.kumar@...il.com>
Subject: Re: [RFC][PATCH 1/7]ext4: Add EXT4_IOC_ADD_GLOBAL_ALLOC_RULE 
	restricts block allocation

Aneesh,

Can you provide the below requested info?

Thanks
Greg

On Tue, Jun 23, 2009 at 8:11 PM, Andreas Dilger<adilger@....com> wrote:
> 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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