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Re: DMAPI and dump/restore

To: James A Goodwin <jagoodwi@xxxxxxxxxx>
Subject: Re: DMAPI and dump/restore
From: Timothy Shimmin <tes@xxxxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 10 Jul 2001 12:47:59 +1000
Cc: "linux-xfs@xxxxxxxxxxx" <linux-xfs@xxxxxxxxxxx>
In-reply-to: <OF863FBA34.3C7B6B8D-ON86256A84.0051D026@LocalDomain>; from jagoodwi@xxxxxxxxxx on Mon, Jul 09, 2001 at 10:05:37AM -0500
References: <OF863FBA34.3C7B6B8D-ON86256A84.0051D026@LocalDomain>
Sender: owner-linux-xfs@xxxxxxxxxxx
Hi James,

On Mon, Jul 09, 2001 at 10:05:37AM -0500, James A Goodwin wrote:
> Does anyone know the extent to which DMAPI information is handled by
> xfsdump/xfsrestore?  There are two things that worry me:
> 
> 1. Are xfsdump/xfsrestore smart enough to realize when data is not resident
> on XFS disks?  In other words, the data has been migrated by the DMAPI
> client, and dm_puch_hole() was used to free up the XFS disk resources.
> When doing a dump, I'd rather have xfsdump note that there is a hole rather
> than dredging all the migrated data back up through the DMAPI.
> 
> The xfsdump man page mentions a "-a" option for
> working with DMF that sounds a lot like an answer to #1, but I'd be
> surprised if there was any relationship between DMF and DMAPI.
>
I'm not that "au fait" with DMAPI stuff - Dean (roehrich@xxxxxxx)
would be the one with answers to such questions :)

However,
the "-a" option is used to dump DMF dual-state and unmigrating
files as offline (so no data is dumped). 
Looking at the code,
   - its extent data will be dumped as 1 extent with a hole
     (so the data aint dumped)
   - its DMF attributes won't be dumped but a replacement DMF attribute 
     (i.e. DMF_ST_OFFLINE) will be dumped in its place
   - the stat buf's bs_devmask will be or'ed with DM_EVENT_READ

(I don't know if this is enought for all DMAPI users or just DMF ?)

Having said that, all the relevant code is #ifdef'ed out
by the DMEXTATTR macro, and DMEXTATTR is commented out in the Makefile
for LCFLAGS.
Andrew Gildfind (ajag@xxxxxxx) did this, I believe as the
DMAPI code wasn't complete at the time.
Turning it back on may require some porting issues. 
Any comments, Andrew ?
Someone should look into getting this going.

> 2. What do xfsdump/xfsrestore do with DM attributes, regions, and event
> lists?  Are they stored, ignored, or something else?
> 
I presumed all the DMAPI event stuff and other related data is
in extended attributes. And all the extended attributes are
dumped out (unless the -A option is used).


Hmmmm....xfsrestore takes the -D option to restore DMAPI event
settings. If F_FSSETDM macro is set then it uses fcntl(F_FSSETDM).
All this code is #ifdef'ed out by the macro F_FSSETDM.
This doesn't seem to be turned on in IRIX or Linux.
Dean, is it not necessary to call fcntl(F_FSSETDM) ?
Thanks.


Cheers,
--Tim

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