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Re: [RFC] add FIEMAP ioctl to efficiently map file allocation

To: Anton Altaparmakov <aia21@xxxxxxxxx>, linux-ext4@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, hch@xxxxxxxxxxxxx
Subject: Re: [RFC] add FIEMAP ioctl to efficiently map file allocation
From: Jeff Mahoney <jeffm@xxxxxxxx>
Date: Fri, 13 Apr 2007 10:53:50 -0400
In-reply-to: <20070413040156.GU5967@xxxxxxxxxxxxxxxxxxxx>
Organization: SUSE Labs, Novell, Inc
References: <20070412110550.GM5967@xxxxxxxxxxxxxxxxxxxx> <97211C89-1810-4B22-B2F4-9D206D43C1F6@xxxxxxxxx> <20070413040156.GU5967@xxxxxxxxxxxxxxxxxxxx>
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Andreas Dilger wrote:
> On Apr 12, 2007  12:22 +0100, Anton Altaparmakov wrote:
>> This would say that the offset on disk can move at any time or that  
>> the data is compressed or encrypted on disk thus the data is not  
>> useful for direct disk access.
> 
> This makes sense.  Even for Reiserfs the same is true with packed tails,
> and I believe if FIBMAP is called on a tail it will migrate the tail into
> a block because this is might be a sign that the file is a kernel that
> LILO wants to boot.

Actually, reiserfs_aop_bmap() returns 0 when the requested block is in a
tail. There's a separate ioctl for unpacking them.

- -Jeff

- --
Jeff Mahoney
SUSE Labs
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