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Re: [PATCH 2/6] fiemap: add fe_phys_length and EXTENT_PHYS_LENGTH flag

To: David Sterba <dsterba@xxxxxxx>
Subject: Re: [PATCH 2/6] fiemap: add fe_phys_length and EXTENT_PHYS_LENGTH flag
From: Andreas Dilger <adilger@xxxxxxxxx>
Date: Wed, 30 Jul 2014 14:06:16 -0600
Cc: linux-fsdevel@xxxxxxxxxxxxxxx, hch@xxxxxxxxxxxxx, mfasheh@xxxxxxxx, viro@xxxxxxxxxxxxxxxxxx, david@xxxxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-nilfs@xxxxxxxxxxxxxxx, ocfs2-devel@xxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, linux-btrfs@xxxxxxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <f257ce29393707293c0ce056bd8c6a7b3daa6082.1406739708.git.dsterba@xxxxxxx>
References: <cover.1406739708.git.dsterba@xxxxxxx> <f257ce29393707293c0ce056bd8c6a7b3daa6082.1406739708.git.dsterba@xxxxxxx>
On Jul 30, 2014, at 11:18 AM, David Sterba <dsterba@xxxxxxx> wrote:
> Add a new member to fiemap_extent that represents the physical extent
> length. This value is undefined if the flag EXTENT_PHYS_LENGTH is not
> set.

The description here of PHYS_LENGTH makes sense...

The patch description should also mention the name of the new member,
namely "fe_phys_length"

> +#define FIEMAP_EXTENT_PHYS_LENGTH    0x00000010 /* Physical length of extent
> +                                                 * not the same as logical */

But the comment doesn't match.  This implies that if PHYS_LENGTH is
set, fe_phys_length != fe_logi_length, but I don't think that is
necessarily correct.  I think it makes more sense to just set
PHYS_LENGTH when fe_phys_length is valid, and if PHYS_LENGTH is not
set then fe_phys_length aware applications should just use
fe_phys_length = fe_logi_length, and older applications would just
use fe_length for both as they would already today.

Cheers, Andreas

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