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Re: retrieving exteneded attributes speed issues

To: Nathan Scott <nathans@xxxxxxx>
Subject: Re: retrieving exteneded attributes speed issues
From: Tim Shimmin <tes@xxxxxxx>
Date: Mon, 3 Jun 2002 13:43:10 +1000
Cc: anmar@xxxxxxxxxx, linux-xfs@xxxxxxxxxxx
In-reply-to: <20020601125351.X207538@xxxxxxxxxxxxxxxxxxxxxxxx>; from nathans@xxxxxxx on Sat, Jun 01, 2002 at 12:53:51PM +1000
References: <3CF7DB07.2060205@xxxxxxxxxxxxxxxxxxxxxx> <20020601125351.X207538@xxxxxxxxxxxxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
On Sat, Jun 01, 2002 at 12:53:51PM +1000, Nathan Scott wrote:
> hi,
> 
> On Fri, May 31, 2002 at 01:20:23PM -0700, Anmar Oueja wrote:
> > What's the best way of efficiently retrieving all extended attributes of
> > a file on an XFS partition?
> > 
> > Now I'm doing what the utility getattr does:
> 
> 
[...stuff deleted...]
> There is another solution as well, as Steve has pointed out - xfsdump
> uses some XFS-specific ioctl's to get back multiple attribute values
> at once.  Such a program would only work on XFS filesystems though,
> where as getfattr will work for all filesystems supporting EAs.
> 
On IRIX and old linux-xfs, a low syscall count solution for
what you want is attr_multi (and attr_list). 
It would for instance, allow you to get all the values for a list of names
in 2 syscalls.
However, with the syscall reorg, attr_multi is now done as
multiple syscalls. 

xfsdump uses jdm_attr_list and jdm_attr_multi (these have been retained).
jdm_attr_list is used to get the list of names and valuelen's
to put into a multi struct, and jdm_attr_multi is used to
get all the values in one syscall.
These are done as single ioctls so retain the efficiency.

I'm not so famiiliar with the jdm_*() calls, but I
think one would need to call jdm_getfshandle(mntpt)
to get an fshandle, and one also needs an xfs_bstat_t
(for an ino#/gen#) which one normally gets from
a bulkstat ioctl (XFS_IOC_FSBULKSTAT, XFS_IOC_FSBULKSTAT_SINGLE). 

--Tim


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