linux-kernel - RE: [RFC PATCH v2 2/3] device-dax: use fallback nid when numa

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Date:   Tue, 7 Jul 2020 06:08:21 +0000
From:   Justin He <Justin.He@....com>
To:     Justin He <Justin.He@....com>
CC:     Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Baoquan He <bhe@...hat.com>,
        Chuhong Yuan <hslester96@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        Kaly Xin <Kaly.Xin@....com>,
        Catalin Marinas <Catalin.Marinas@....com>,
        Will Deacon <will@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Subject: RE: [RFC PATCH v2 2/3] device-dax: use fallback nid when numa_node is
 invalid

[+] add Powerpc maintainers to check my concern about memory_add_physaddr_to_nid
Exporting


--
Cheers,
Justin (Jia He)



> -----Original Message-----
> From: Jia He <justin.he@....com>
> Sent: Tuesday, July 7, 2020 1:59 PM
> To: Catalin Marinas <Catalin.Marinas@....com>; Will Deacon
> <will@...nel.org>; Dan Williams <dan.j.williams@...el.com>; Vishal Verma
> <vishal.l.verma@...el.com>; Dave Jiang <dave.jiang@...el.com>
> Cc: Michal Hocko <mhocko@...e.com>; Andrew Morton <akpm@...ux-
> foundation.org>; Mike Rapoport <rppt@...ux.ibm.com>; Baoquan He
> <bhe@...hat.com>; Chuhong Yuan <hslester96@...il.com>; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; linux-
> mm@...ck.org; linux-nvdimm@...ts.01.org; Kaly Xin <Kaly.Xin@....com>;
> Justin He <Justin.He@....com>
> Subject: [RFC PATCH v2 2/3] device-dax: use fallback nid when numa_node is
> invalid
> 
> Previously, numa_off is set unconditionally at the end of
> dummy_numa_init(),
> even with a fake numa node. Then ACPI detects node id as NUMA_NO_NODE(-1)
> in
> acpi_map_pxm_to_node() because it regards numa_off as turning off the numa
> node. Hence dev_dax->target_node is NUMA_NO_NODE on arm64 with fake numa.
> 
> Without this patch, pmem can't be probed as a RAM device on arm64 if SRAT
> table
> isn't present:
> $ndctl create-namespace -fe namespace0.0 --mode=devdax --map=dev -s 1g -a
> 64K
> kmem dax0.0: rejecting DAX region [mem 0x240400000-0x2bfffffff] with
> invalid node: -1
> kmem: probe of dax0.0 failed with error -22
> 
> This fixes it by using fallback memory_add_physaddr_to_nid() as nid.
> 
> Suggested-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Jia He <justin.he@....com>
> ---
> I noticed that on powerpc memory_add_physaddr_to_nid is not exported for
> module
> driver. Set it to RFC due to this concern.
> 
>  drivers/dax/kmem.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> index 275aa5f87399..68e693ca6d59 100644
> --- a/drivers/dax/kmem.c
> +++ b/drivers/dax/kmem.c
> @@ -28,20 +28,22 @@ int dev_dax_kmem_probe(struct device *dev)
>  	resource_size_t kmem_end;
>  	struct resource *new_res;
>  	const char *new_res_name;
> -	int numa_node;
> +	int numa_node, new_node;
>  	int rc;
> 
>  	/*
>  	 * Ensure good NUMA information for the persistent memory.
> -	 * Without this check, there is a risk that slow memory
> -	 * could be mixed in a node with faster memory, causing
> -	 * unavoidable performance issues.
> +	 * Without this check, there is a risk but not fatal that slow
> +	 * memory could be mixed in a node with faster memory, causing
> +	 * unavoidable performance issues. Furthermore, fallback node
> +	 * id can be used when numa_node is invalid.
>  	 */
>  	numa_node = dev_dax->target_node;
>  	if (numa_node < 0) {
> -		dev_warn(dev, "rejecting DAX region %pR with invalid
> node: %d\n",
> -			 res, numa_node);
> -		return -EINVAL;
> +		new_node = memory_add_physaddr_to_nid(kmem_start);
> +		dev_info(dev, "changing nid from %d to %d for DAX
> region %pR\n",
> +			numa_node, new_node, res);
> +		numa_node = new_node;
>  	}
> 
>  	/* Hotplug starting at the beginning of the next block: */
> @@ -100,6 +102,7 @@ static int dev_dax_kmem_remove(struct device *dev)
>  	resource_size_t kmem_start = res->start;
>  	resource_size_t kmem_size = resource_size(res);
>  	const char *res_name = res->name;
> +	int numa_node = dev_dax->target_node;
>  	int rc;
> 
>  	/*
> @@ -108,7 +111,10 @@ static int dev_dax_kmem_remove(struct device *dev)
>  	 * there is no way to hotremove this memory until reboot because
> device
>  	 * unbind will succeed even if we return failure.
>  	 */
> -	rc = remove_memory(dev_dax->target_node, kmem_start, kmem_size);
> +	if (numa_node < 0)
> +		numa_node = memory_add_physaddr_to_nid(kmem_start);
> +
> +	rc = remove_memory(numa_node, kmem_start, kmem_size);
>  	if (rc) {
>  		any_hotremove_failed = true;
>  		dev_err(dev,
> --
> 2.17.1