linux-ext4 - Re: [PATCH 0/4] FS: userspace notification of errors

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Date:	Wed, 10 Jun 2009 23:05:07 +0200
From:	Pavel Machek <pavel@....cz>
To:	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Karpov Denis.2 (EXT-Teleca/Helsinki)" <ext-denis.2.karpov@...ia.com>,
	"axboe@...nel.dk" <axboe@...nel.dk>,
	"hirofumi@...l.parknet.co.jp" <hirofumi@...l.parknet.co.jp>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Hunter Adrian (Nokia-D/Helsinki)" <adrian.hunter@...ia.com>
Subject: Re: [PATCH 0/4] FS: userspace notification of errors

On Thu 2009-06-04 08:57:58, Artem Bityutskiy wrote:
> Andrew Morton wrote:
>> hm, I'm uncertain on the desirability or otherwise of the overall feature.
>>
>> Are there users or distros or device manufacturers asking for this?  
>> Where did the requirement come from?
>>
>> What downstream application will handle the uevent messages?  Do you
>> have some userspace design/plan in mind?
>>
>> IOW, it would be useful if we were told more about all of this, rather
>> than just staring at a kernel patch!
>
> As the original idea came from me, while whole implementation
> and design was done by Denis, I'll comment on this.
>
> Our use-case is about hand-held devices. We are particularly
> working with large FAT volumes on MMC. Do not question please
> why it is FAT and not something else :-) Anyway, FAT is very
> unreliable, and often hits errors, in which case it simply
> switches to read-only mode, and usually prints something to
> the printk ring buffer.

So fsck the mmc card on card insertion...? fsck.vfat on flash is
pretty fast operation (as it onl needs to read directories +
FATs). Android 1.5 implements this.

...otherwise you will loose data on two files sharing clusters, will
never recover lost clusters, etc.

Perhaps it would be feasible  to permit read-only mount of unclean
VFAT, run fsck in background, and buffer any changes in memory until
fsck finishes?

									Pavel

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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