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Re: Extended attributes limit in Linux

To: Jeff Liu <jeff.liu@xxxxxxxxxx>, xfs@xxxxxxxxxxx
Subject: Re: Extended attributes limit in Linux
From: Sun_Blood <sblood@xxxxxxxxx>
Date: Fri, 31 Jan 2014 20:25:08 +0100
Cc: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
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On 31 jan 2014, at 15:33, Jeff Liu <jeff.liu@xxxxxxxxxx> wrote:

> 
> On 01/31 2014 22:21 PM, Vyacheslav Dubeyko wrote:
>> On Fri, 2014-01-31 at 21:39 +0800, Jeff Liu wrote:
>> 
>>>> 
>>>> I checked the same under Mac OS X 10.6.8 (Snow Leopard). And I have
>>>> failed on 3803 bytes size of xattr. So, I suppose that you have Mac OS X
>>>> Lion. And EAs is larger under Lion yet.
>>>> 
>>>> What version of Mac OS X have you?
>>>> 
>>> Yup, Mountain Lion v10.8.4 :)
>>> 
>> 
>> I suspect that xattrs with significant size is stored in compressed
>> state on HFS+. I implemented support of compressed xattrs partially but
>> I don't share this code yet. But, yes, EAs with size greater than 64 KB
>> can be a problem.


FYI, Example of output from one of the failing files. First from OS X and then 
same file after failed copy to XFS.

OS X Maverik:
file: "/Users/username/Pictures/iPhoto Library/Database/apdb/BigBlobs.apdb"
type: "\0\0\0\0"
creator: "\0\0\0\0"
attributes: avbstclinmedz
created: 01/25/2014 11:43:17
modified: 01/28/2014 20:02:46


Ubunutu 
getfattr: Removing leading '/' from absolute path names
# file: srv/nas/home/apple_bak_rsync/username/Pictures/iPhoto 
Library/Database/BigBlobs.apdb
user.com.apple.quarantine="0006;52e39545;iPhoto;”

>> 
>>> FYI, there have a couple of things regarding HFSPlus+xattr+acl on Linux 
>>> might be
>>> deserved to discuss together.
>>> 
>>> We once have a discussion about the errno in case of hit the limits of 
>>> ACLs, which
>>> could be referred to:
>>> http://www.spinics.net/lists/linux-fsdevel/msg71125.html
>>> 
>>> HFSPlus return ENOMEM in this case, but it should be E2BIG as per Dave's 
>>> comments.
>>> I worked out a patch series includes HFSPlus, but not yet posted for some 
>>> reasons.
>>> 
>>> Also, it seems to me we'd better consolidate the errno for EA as well, that 
>>> is to
>>> say, it's better to fix the return error to be consistent with VFS 
>>> interface in case
>>> of the given EA name/value length is larger than the specified limits.
>>> 
>>> Would you like to take a look at the following two patches?
>>> 
>> 
>> Yes, sure. Patches looks correct and good for me. But did you take into
>> account recent significant changes of Christoph Hellwig? If so, then all
>> looks good.
> 
> Thanks for the review.  That's one major reason I postpone the patch set 
> submission
> as I did it before Christoph's changes got merged, it looks like no obvious 
> conflicts
> with that, but I will find time to double check and sent it to you -- still 
> on vacation
> for Chinese Spring Festival.
> 
> Thanks,
> -Jeff

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