linux-ext4 - Re: [RFC][PATCH 7/9]ext4: Add the EXT4_IOC_FIEMAP

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Message-ID: <49059633.8080600@rs.jp.nec.com>
Date:	Mon, 27 Oct 2008 19:21:39 +0900
From:	Akira Fujita <a-fujita@...jp.nec.com>
To:	Andreas Dilger <adilger@....com>
CC:	linux-ext4@...r.kernel.org, Theodore Tso <tytso@....edu>,
	Mingming Cao <cmm@...ibm.com>, hch@...radead.org
Subject: Re: [RFC][PATCH 7/9]ext4: Add the EXT4_IOC_FIEMAP_INO ioctl

Hi Andreas,

Andreas Dilger wrote:
> On Oct 24, 2008  19:09 +0900, Akira Fujita wrote:
>> The EXT4_IOC_FIEMAP_INO is used to get extents information of
>> inode which set to ioctl.
>> The defragger uses this ioctl to check the fragment condition
>> and to get extents information in the specified block group.
> 
> Instead of having a separate IOC number for each such ioctl, instead
> we implemented EXT4_IOC_WRAPPER, which is an root-specific ioctl that
> passes in an inode number and a second IOC number so that arbitrary file
> ioctls can be run on any inode by root.

The EXT4_IOC_WRAPPER ioctl seems to be usuful for many situations.
But the EXT4_IOC_FIEMAP_INO ioctl is used not only root user but also
non-root user to call fiemap,
so we cannot use the current EXT4_IOC_WRAPPER ioctl for defrag.

> This was mentioned last time these patches were posted, but there was
> no reply from you.  Christoph suggested a more generic VFS open-by-inum,
> which isn't impossible to do but would cause a lot of controversy I
> think, while the EXT4_IOC_WRAPPER is at least contained within ext4,
> but is more generically useful than EXT4_IOC_FIEMAP_INO.
> 

Do you plan to add EXT4_IOC_WRAPPER into the ext4 patch queue?


Regards,
Akira Fujita
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