linux-ext4 - Re: [PATCH 2/3] ext4: Context support

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Date:	Fri, 22 Jun 2012 16:29:13 +0300
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Arnd Bergmann <arnd.bergmann@...aro.org>
Cc:	Ted Ts'o <tytso@....edu>, Alex Lemberg <Alex.Lemberg@...disk.com>,
	HYOJIN JEONG <syr.jeong@...sung.com>,
	Saugata Das <saugata.das@...aro.org>,
	Saugata Das <saugata.das@...ricsson.com>,
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mmc@...r.kernel.org, patches@...aro.org, venkat@...aro.org,
	"Luca Porzio (lporzio)" <lporzio@...ron.com>
Subject: Re: [PATCH 2/3] ext4: Context support

On Wed, 2012-06-13 at 19:44 +0000, Arnd Bergmann wrote:
> I think using the inode number is a reasonable fit. Using the
> inode number of the parent directory might be more appropriate
> but it breaks with hard links and cross-directory renames (we
> must not use the same LBA with conflicting context numbers,
> or flush the old context inbetween).

I would put it this way.

1. contex = inode number for data blocks.
2. context = parent directory's inode number for stat data (times,
permissions, etc) blocks and directory entry blocks. Should help things
like readdir and readdir + stat. Besides, this stuff tend to change more
often than the data, so mixing it with the data in the same eraseblock
is not smart.
3. context = parent inode number for all the stuff belonging to xattrs.

We do something similar in UBIFS.

-- 
Best Regards,
Artem Bityutskiy

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