linux-kernel - Re: [RFC PATCH 06/13] scsi: scsi_dh: ufshpb: Prepare for L2P cache management

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Date:   Fri, 15 May 2020 19:13:29 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Avri Altman <avri.altman@....com>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     alim.akhtar@...sung.com, asutoshd@...eaurora.org,
        Zang Leigang <zangleigang@...ilicon.com>,
        Avi Shchislowski <avi.shchislowski@....com>,
        Bean Huo <beanhuo@...ron.com>, cang@...eaurora.org,
        stanley.chu@...iatek.com,
        MOHAMMED RAFIQ KAMAL BASHA <md.rafiq@...sung.com>,
        Sang-yoon Oh <sangyoon.oh@...sung.com>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        Jinyoung CHOI <j-young.choi@...sung.com>
Subject: Re: [RFC PATCH 06/13] scsi: scsi_dh: ufshpb: Prepare for L2P cache
 management

On 2020-05-15 03:30, Avri Altman wrote:
> +static int ufshpb_mempool_init(struct ufshpb_dh_lun *hpb)
> +{
> +	unsigned int max_active_subregions = hpb->max_active_regions *
> +		subregions_per_region;
> +	int i;
> +
> +	INIT_LIST_HEAD(&hpb->lh_map_ctx);
> +	spin_lock_init(&hpb->map_list_lock);
> +
> +	for (i = 0 ; i < max_active_subregions; i++) {
> +		struct ufshpb_map_ctx *mctx =
> +			kzalloc(sizeof(struct ufshpb_map_ctx), GFP_KERNEL);
> +
> +		if (!mctx) {
> +			/*
> +			 * mctxs already added in lh_map_ctx will be removed in
> +			 * detach
> +			 */
> +			return -ENOMEM;
> +		}
> +
> +		/* actual page allocation is done upon subregion activation */
> +
> +		INIT_LIST_HEAD(&mctx->list);
> +		list_add(&mctx->list, &hpb->lh_map_ctx);
> +	}
> +
> +	return 0;
> +
> +}

Could kmem_cache_create() have been used instead of implementing yet
another memory pool implementation?

> +static int ufshpb_region_tbl_init(struct ufshpb_dh_lun *hpb)
> +{
> +	struct ufshpb_region *regions;
> +	int i, j;
> +
> +	regions = kcalloc(hpb->regions_per_lun, sizeof(*regions), GFP_KERNEL);
> +	if (!regions)
> +		return -ENOMEM;
> +
> +	atomic_set(&hpb->active_regions, 0);
> +
> +	for (i = 0 ; i < hpb->regions_per_lun; i++) {
> +		struct ufshpb_region *r = regions + i;
> +		struct ufshpb_subregion *subregions;
> +
> +		subregions = kcalloc(subregions_per_region, sizeof(*subregions),
> +				     GFP_KERNEL);
> +		if (!subregions)
> +			goto release_mem;
> +
> +		for (j = 0; j < subregions_per_region; j++) {
> +			struct ufshpb_subregion *s = subregions + j;
> +
> +			s->hpb = hpb;
> +			s->r = r;
> +			s->region = i;
> +			s->subregion = j;
> +		}
> +
> +		r->subregion_tbl = subregions;
> +		r->hpb = hpb;
> +		r->region = i;
> +	}
> +
> +	hpb->region_tbl = regions;
> +
> +	return 0;

Could kvmalloc() have been used to allocate multiple subregion data
structures instead of calling kcalloc() multiple times?

> +	spin_lock(&hpb->map_list_lock);
> +
> +	list_for_each_entry_safe(mctx, next, &hpb->lh_map_ctx, list) {
> +		list_del(&mctx->list);
> +		kfree(mctx);
> +	}
> +
> +	spin_unlock(&hpb->map_list_lock);

Spinlocks should be held during a short time. I'm not sure that's the
case for the above loop.

Thanks,

Bart.