linux-kernel - Re: [PATCH 4/7][TAKE5] support new modes in fallocate

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Date:	Wed, 04 Jul 2007 15:37:01 +1000
From:	Timothy Shimmin <tes@....com>
To:	"Amit K. Arora" <aarora@...ux.vnet.ibm.com>
CC:	Christoph Hellwig <hch@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-ext4@...r.kernel.org, adilger@...sterfs.com,
	David Chinner <dgc@....com>, suparna@...ibm.com,
	cmm@...ibm.com, xfs@....sgi.com
Subject: Re: [PATCH 4/7][TAKE5] support new modes in fallocate

Amit K. Arora wrote:
>>>> FA_FL_NO_MTIME	0x10 /* keep same mtime (default change on size, data change) */
>>>> FA_FL_NO_CTIME	0x20 /* keep same ctime (default change on size, data change) */
>> NACK to these aswell.  If i_size changes c/mtime need updates, if the size
>> doesn't chamge they don't.  No need to add more flags for this.
> 
> This requirement was from the point of view of HSM applications. Hope
> you saw Andreas previous post and are keeping that in mind.
> 
We use this capability in XFS at the moment.
I think this is mainly for DMF (HSM) but is done via the xfs handle interface
(xfs_open_by_handle) AFAICT.

This sets up a set of invisible operations (xfs_invis_file_operations).
xfs_file_ioctl_invis goes on to set IO_INVIS which goes on to set ATTR_DMI
which is then tested in xfs_change_file_space() (which handles XFS_IOC_RESVSP & friends)
for whether xfs_ichgtime(ip, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG)
is called or not.

--Tim
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