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From:   =?utf-8?Q?Javier_Gonz=C3=A1lez?= <javier@javigon.com>
Message-Id: <2608BA38-98D6-487C-BC50-45799D5DEE18@javigon.com>
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Subject: Re: [PATCH V2] lightnvm: pblk: extend line wp balance check
Date:   Wed, 30 Jan 2019 10:38:49 +0100
In-Reply-To: <20190130081857.6779-1-hans@owltronix.com>
Cc:     =?utf-8?Q?Matias_Bj=C3=B8rling?= <mb@lightnvm.io>,
        Zhoujie Wu <zjwu@marvell.com>, linux-block@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Hans Holmberg <hans.holmberg@cnexlabs.com>
To:     Hans Holmberg <hans@owltronix.com>
References: <20190130081857.6779-1-hans@owltronix.com>
Sender: linux-kernel-owner@vger.kernel.org
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> On 30 Jan 2019, at 09.18, hans@owltronix.com wrote:
>=20
> From: Hans Holmberg <hans.holmberg@cnexlabs.com>
>=20
> pblk stripes writes of minimal write size across all non-offline =
chunks
> in a line, which means that the maximum write pointer delta should not
> exceed the minimal write size.
>=20
> Extend the line write pointer balance check to cover this case, and
> ignore the offline chunk wps.
>=20
> This will render us a warning during recovery if something unexpected
> has happened to the chunk write pointers (i.e. powerloss,  a spurious
> chunk reset, ..).
>=20
> Reported-by: Zhoujie Wu <zjwu@marvell.com>
> Tested-by: Zhoujie Wu <zjwu@marvell.com>
> Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
> ---
>=20
> Changes since V1:
>=20
> 	* Squashed with Zhoujie's:
> 	 "lightnvm: pblk: ignore bad block wp for =
pblk_line_wp_is_unbalanced"
> 	* Clarified commit message based on Javier's comments.
>=20
>=20
> drivers/lightnvm/pblk-recovery.c | 56 ++++++++++++++++++++++----------
> 1 file changed, 38 insertions(+), 18 deletions(-)
>=20
> diff --git a/drivers/lightnvm/pblk-recovery.c =
b/drivers/lightnvm/pblk-recovery.c
> index 6761d2afa4d0..d86f580036d3 100644
> --- a/drivers/lightnvm/pblk-recovery.c
> +++ b/drivers/lightnvm/pblk-recovery.c
> @@ -302,35 +302,55 @@ static int pblk_pad_distance(struct pblk *pblk, =
struct pblk_line *line)
> 	return (distance > line->left_msecs) ? line->left_msecs : =
distance;
> }
>=20
> -static int pblk_line_wp_is_unbalanced(struct pblk *pblk,
> -				      struct pblk_line *line)
> +/* Return a chunk belonging to a line by stripe(write order) index */
> +static struct nvm_chk_meta *pblk_get_stripe_chunk(struct pblk *pblk,
> +						  struct pblk_line =
*line,
> +						  int index)
> {
> 	struct nvm_tgt_dev *dev =3D pblk->dev;
> 	struct nvm_geo *geo =3D &dev->geo;
> -	struct pblk_line_meta *lm =3D &pblk->lm;
> 	struct pblk_lun *rlun;
> -	struct nvm_chk_meta *chunk;
> 	struct ppa_addr ppa;
> -	u64 line_wp;
> -	int pos, i;
> +	int pos;
>=20
> -	rlun =3D &pblk->luns[0];
> +	rlun =3D &pblk->luns[index];
> 	ppa =3D rlun->bppa;
> 	pos =3D pblk_ppa_to_pos(geo, ppa);
> -	chunk =3D &line->chks[pos];
>=20
> -	line_wp =3D chunk->wp;
> +	return &line->chks[pos];
> +}
>=20
> -	for (i =3D 1; i < lm->blk_per_line; i++) {
> -		rlun =3D &pblk->luns[i];
> -		ppa =3D rlun->bppa;
> -		pos =3D pblk_ppa_to_pos(geo, ppa);
> -		chunk =3D &line->chks[pos];
> +static int pblk_line_wps_are_unbalanced(struct pblk *pblk,
> +				      struct pblk_line *line)
> +{
> +	struct pblk_line_meta *lm =3D &pblk->lm;
> +	int blk_in_line =3D lm->blk_per_line;
> +	struct nvm_chk_meta *chunk;
> +	u64 max_wp, min_wp;
> +	int i;
> +
> +	i =3D find_first_zero_bit(line->blk_bitmap, blk_in_line);
>=20
> -		if (chunk->wp > line_wp)
> +	/* If there is one or zero good chunks in the line,
> +	 * the write pointers can't be unbalanced.
> +	 */
> +	if (i >=3D (blk_in_line - 1))
> +		return 0;
> +
> +	chunk =3D pblk_get_stripe_chunk(pblk, line, i);
> +	max_wp =3D chunk->wp;
> +	if (max_wp > pblk->max_write_pgs)
> +		min_wp =3D max_wp - pblk->max_write_pgs;
> +	else
> +		min_wp =3D 0;
> +
> +	i =3D find_next_zero_bit(line->blk_bitmap, blk_in_line, i + 1);
> +	while (i < blk_in_line) {
> +		chunk =3D pblk_get_stripe_chunk(pblk, line, i);
> +		if (chunk->wp > max_wp || chunk->wp < min_wp)
> 			return 1;
> -		else if (chunk->wp < line_wp)
> -			line_wp =3D chunk->wp;
> +
> +		i =3D find_next_zero_bit(line->blk_bitmap, blk_in_line, =
i + 1);
> 	}
>=20
> 	return 0;
> @@ -356,7 +376,7 @@ static int pblk_recov_scan_oob(struct pblk *pblk, =
struct pblk_line *line,
> 	int ret;
> 	u64 left_ppas =3D pblk_sec_in_open_line(pblk, line) - =
lm->smeta_sec;
>=20
> -	if (pblk_line_wp_is_unbalanced(pblk, line))
> +	if (pblk_line_wps_are_unbalanced(pblk, line))
> 		pblk_warn(pblk, "recovering unbalanced line (%d)\n", =
line->id);
>=20
> 	ppa_list =3D p.ppa_list;
> --
> 2.17.1

Looks good to me.

Reviewed-by: Javier Gonz=C3=A1lez <javier@javigon.com>


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