linux-kernel - Re: [PATCH] UBI: flush wl before clearing update marker

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Message-ID: <20091202154223.GA5895@suse.de>
Date:	Wed, 2 Dec 2009 07:42:23 -0800
From:	Greg KH <gregkh@...e.de>
To:	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
Cc:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>,
	stable@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] UBI: flush wl before clearing update marker

On Wed, Dec 02, 2009 at 08:48:43AM +0200, Artem Bityutskiy wrote:
> From: Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
> 
> ubiupdatevol -t does the following:
> - ubi_start_update()
>   - set_update_marker()
>   - for all LEBs ubi_eba_unmap_leb()
>   - clear_update_marker()
>   - ubi_wl_flush()
> 
> ubi_wl_flush() physically erases all PEB, once it returns all PEBs are
> empty. clear_update_marker() has the update marker written after return.
> If there is a power cut between the last two functions then the UBI
> volume has no longer the "update" marker set and may have some valid
> LEBs while some of them may be gone.
> If that volume in question happens to be a UBIFS volume, then mount
> will fail with
> 
> |UBIFS error (pid 1361): ubifs_read_node: bad node type (255 but expected 6)
> |UBIFS error (pid 1361): ubifs_read_node: bad node at LEB 0:0
> |Not a node, first 24 bytes:
> |00000000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> 
> if there is at least one valid LEB and the wear-leveling worker managed
> to clear LEB 0.
> 
> The patch waits for the wl worker to finish prior clearing the "update"
> marker on flash. The two new LEB which are scheduled for erasing after
> clear_update_marker() should not matter because they are only visible to
> UBI.
> 
> Signed-off-by: Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
> Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
> Cc: stable@...nel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/mtd/ubi/upd.c |   20 +++++++++++---------


I'm not the mtd or ubi maintainer, so why did you send this to me?

confused,

greg k-h
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