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From: Christoph Hellwig <hch@lst.de>
To: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Cc: kbusch@kernel.org, hch@lst.de, linux-nvme@lists.infradead.org,
	sagi@grimberg.me
Subject: Re: [PATCH V2 2/2] nvmet: use xarray for ctrl ns storing
Date: Wed, 1 Jul 2020 08:08:20 +0200
Message-ID: <20200701060820.GA28214@lst.de> (raw)
In-Reply-To: <20200701022517.6738-3-chaitanya.kulkarni@wdc.com>

Ok, for the target I can see how this makes sense unlike the host.
Comments below:

> -	u64 host_reads = 0, host_writes = 0;
>  	u64 data_units_read = 0, data_units_written = 0;
> -	struct nvmet_ns *ns;
> +	u64 host_reads = 0, host_writes = 0;
>  	struct nvmet_ctrl *ctrl;
> +	struct nvmet_ns *ns;
> +	unsigned long idx;

Please don't randomly reorder the variable declarations.  Same for
later function.

> diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
> index cea7c3834021..d14edaa22ad5 100644
> --- a/drivers/nvme/target/core.c
> +++ b/drivers/nvme/target/core.c
> @@ -10,6 +10,9 @@
>  #include <linux/pci-p2pdma.h>
>  #include <linux/scatterlist.h>
>  
> +#include "../host/nvme.h"
> +#undef CREATE_TRACE_POINTS

We really shoud not include the host nvme.h in the target code.  What
are you trying to get from it?

>  static unsigned int nvmet_max_nsid(struct nvmet_subsys *subsys)
>  {
> -	struct nvmet_ns *ns;
> +	struct nvmet_ns *cur;
> +	unsigned long idx;
> +	unsigned long nsid;
>  
> -	if (list_empty(&subsys->namespaces))
> +	if (xa_empty(&subsys->namespaces))
>  		return 0;
>  
> -	ns = list_last_entry(&subsys->namespaces, struct nvmet_ns, dev_link);
> -	return ns->nsid;
> +	xa_for_each(&subsys->namespaces, idx, cur)
> +		nsid = cur->nsid;
> +
> +	return nsid;

No need for the xa_empty here.  I also forwarded a question to Matthew
if there is a better way to find the highest index.

>  struct nvmet_ns *nvmet_find_namespace(struct nvmet_ctrl *ctrl, __le32 nsid)
>  {
> +	XA_STATE(xas, &ctrl->subsys->namespaces, le32_to_cpu(nsid));
> +	struct nvmet_ns *ns = NULL;
>  
>  	rcu_read_lock();
> +	do {
> +		ns = xas_load(&xas);
> +		if (xa_is_zero(ns))
> +			ns = NULL;
> +	} while (xas_retry(&xas, ns));
>  	if (ns)
>  		percpu_ref_get(&ns->ref);
>  	rcu_read_unlock();

Why doesn't this use xa_load?

> +	ret = xa_insert(&subsys->namespaces, ns->nsid, ns, GFP_KERNEL);
> +	if (ret) {
> +		switch (ret) {
> +		case -ENOMEM:
> +			pr_err("xa insert memory allocation\n");
> +			goto out_unlock;
> +		case -EBUSY:
> +			pr_err("xa insert entry already present\n");
> +			goto out_unlock;
> +		default:
> +			goto out_unlock;
>  		}
>  	}
> +

I don't think we need the switch statement, just return any error
encountered.

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Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-01  2:25 [PATCH V2 0/2] nvme: replace linked list with xarray for ns tracking Chaitanya Kulkarni
2020-07-01  2:25 ` [PATCH V2 1/2] nvme-core: use xarray for ctrl " Chaitanya Kulkarni
2020-07-01 13:12   ` Christoph Hellwig
2020-07-01 16:44     ` Keith Busch
2020-07-01 18:19     ` Chaitanya Kulkarni
2020-07-01 18:29       ` Keith Busch
2020-07-01 18:40         ` Chaitanya Kulkarni
2020-07-01  2:25 ` [PATCH V2 2/2] nvmet: use xarray for ctrl ns storing Chaitanya Kulkarni
2020-07-01  6:08   ` Christoph Hellwig [this message]
2020-07-01 18:36     ` Chaitanya Kulkarni
2020-07-01  5:36 ` [PATCH V2 0/2] nvme: replace linked list with xarray for ns tracking Christoph Hellwig
2020-07-01 13:21   ` Keith Busch
2020-07-01 16:49     ` Sagi Grimberg
2020-07-01 18:43       ` Chaitanya Kulkarni
2020-07-01 18:41     ` Chaitanya Kulkarni
2020-07-01 18:41   ` Chaitanya Kulkarni

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