linux-kernel - Re: [PATCH V1 00/17] ext4: Add inline data support.

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Message-ID: <4EA962B2.3030402@tao.ma>
Date:	Thu, 27 Oct 2011 21:54:58 +0800
From:	Tao Ma <tm@....ma>
To:	Valdis.Kletnieks@...edu
CC:	Ted Ts'o <tytso@....edu>,
	ext4 development <linux-ext4@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andreas Dilger <adilger@...ger.ca>
Subject: Re: [PATCH V1 00/17] ext4: Add inline data support.

On 10/27/2011 03:10 PM, Valdis.Kletnieks@...edu wrote:
> On Wed, 26 Oct 2011 15:32:24 +0800, Tao Ma said:
> 
>> Currently I use all the space between i_extra_isize and inode_size if
>> inode_size = 256. For inode_size > 256, half of that space is used so as
>> to leave some space for other xattrs.
> 
> I didn't check the code too closely - does this code DTRT if the user tries to
> then attach a moby-sized xattr (or set of xattrs - if it's got a security.selinux
> tag on it, and a security.capabilities xattr, and a user xattr or two, things are
> going to be getting full).
sure, it will work and all these stuff will be inserted to the external
xattr block since the in-inode space is full.
> 
>> This is only a V1 and there are still something to do(e.g. I am thinking
>> of using unused extent space), but I'd like to send it out earlier so
>> that it can be reviewed ASAP.
> 
> If this works out, would it make sense to investigate doing this for all
> tails in a V2?  So if your file was 4099 bytes long, you could save allocating
> a second block.  Assuming random distribution of tail sizes, this wil save
> an average of (space avail for tail)/(blocksize) per file.
uh, it seems like a good suggestion, but it will make the code a little
bit complicated(at least compared to the current version) and I am not
sure whether the maintainer like it or not ;) . So Ted and Andreas, What
do you think of this?

Thanks
Tao

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