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Subject: Re: [RFC] [PATCH] UBI: refine wear leveling logic
From: Artem Bityutskiy <dedekind@infradead.org>
To: Alexander Schmidt <alexs@linux.vnet.ibm.com>
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Date: Thu, 29 Mar 2007 13:36:31 +0300
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Hi Alexander,

On Wed, 2007-03-28 at 15:47 +0200, Alexander Schmidt wrote:
> This patch addresses the handling of blocks that are put by the user
> while they are moved by the wear leveling thread. The schedule_erase
> function is now called by put_peb() itself instead of notifying the wear
> leveling thread.

May I ask you for more explanation why you think your code is correct?

> +
> +	if (in_wl_tree(e, &ubi->used))
> +		used_tree_del(ubi, e);
> +	else if (unlikely(in_wl_tree(e, &ubi->scrub)))
> +		scrub_tree_del(ubi, e);
> +	else if (!in_wl_tree(e, &ubi->free))
> +		prot_tree_del(ubi, e->pnum);
>  	spin_unlock(&ubi->wl_lock);
> =20
>  	err =3D schedule_erase(ubi, e, torture);

Fine, you schedule this eraseblock for erasure. At the same time the the
WL worker moves data in there. The copy_leb() function will notice that
the LEB is unmapped, and won't do copy. Then the WL worker will insert
the eraseblock to a tree. At the same time the erase worker will insert
the same wl_entry to the free tree. One of the trees will be screwed-up.

--=20
Best regards,
Artem Bityutskiy (=D0=91=D0=B8=D1=82=D1=8E=D1=86=D0=BA=D0=B8=D0=B9 =D0=90=
=D1=80=D1=82=D1=91=D0=BC)