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Re: Extended attributes limit in Linux

To: Sun_Blood <sblood@xxxxxxxxx>, xfs@xxxxxxxxxxx
Subject: Re: Extended attributes limit in Linux
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Fri, 31 Jan 2014 16:54:52 +0800
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <CAMN6oR=a0G6O-3CVVkTwhYKavJTa543U3MLezCM8KW1ASZcPnA@xxxxxxxxxxxxxx>
References: <CAMN6oR=a0G6O-3CVVkTwhYKavJTa543U3MLezCM8KW1ASZcPnA@xxxxxxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0

On 01/31 2014 15:40 PM, Sun_Blood wrote:
> Hello,
> If I understands it correctly XFS don't have a limit to the size of
> extended attributes(EA) but Linux impose a limit at 64k.
> What I am trying to do is build a backup server that our Apple computers
> will use together with rsync to backup files to. The problem I face is
> that Apple HFS+ don't have a limit to EA so it has files with more then
> 64k of EA in it.
> The Linux Kernel has a limit imposed to it in include/linux/limits.h
>     #defineXATTR_SIZE_MAX 65536   /* size of an extended attribute value
>     (64k) */
>     #defineXATTR_LIST_MAX 65536   /* size of extended attribute namelist
>     (64k) */

Yes, 64k is the VFS limit per EA value size.
> Changing this values feels unsafe because they will be system wide.
> Is the any possibility to combine Linux + XFS to make a backup that
> works with EA or is this more a question for kernel.org <http://kernel.org>?

So if an EA value size on HFS+ is larger than 64k, I suspect it would failed to 
on Linux+XFS... But if a file has multiple EAs, and each EA's value size is <= 
64K, it
would be works IMO.


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