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Message-ID: <874mdhx7mj.fsf@linux.vnet.ibm.com>
Date: Wed, 10 Feb 2016 14:30:20 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: David Gibson <david@...son.dropbear.id.au>, mpe@...erman.id.au,
paulus@...ba.org, benh@...nel.crashing.org
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
David Gibson <david@...son.dropbear.id.au>
Subject: Re: [PATCH 3/4] powerpc/mm: Clean up memory hotplug failure paths
David Gibson <david@...son.dropbear.id.au> writes:
> This makes a number of cleanups to handling of mapping failures during
> memory hotplug on Power:
>
> For errors creating the linear mapping for the hot-added region:
> * This is now reported with EFAULT which is more appropriate than the
> previous EINVAL (the failure is unlikely to be related to the
> function's parameters)
> * An error in this path now prints a warning message, rather than just
> silently failing to add the extra memory.
> * Previously a failure here could result in the region being partially
> mapped. We now clean up any partial mapping before failing.
>
> For errors creating the vmemmap for the hot-added region:
> * This is now reported with EFAULT instead of causing a BUG() - this
> could happen for external reason (e.g. full hash table) so it's better
> to handle this non-fatally
> * An error message is also printed, so the failure won't be silent
> * As above a failure could cause a partially mapped region, we now
> clean this up.
>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> Signed-off-by: David Gibson <david@...son.dropbear.id.au>
> Reviewed-by: Paul Mackerras <paulus@...ba.org>
> ---
> arch/powerpc/mm/hash_utils_64.c | 13 ++++++++++---
> arch/powerpc/mm/init_64.c | 38 ++++++++++++++++++++++++++------------
> arch/powerpc/mm/mem.c | 10 ++++++++--
> 3 files changed, 44 insertions(+), 17 deletions(-)
>
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index 99fbee0..fdcf9d1 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -640,9 +640,16 @@ static unsigned long __init htab_get_table_size(void)
> #ifdef CONFIG_MEMORY_HOTPLUG
> int create_section_mapping(unsigned long start, unsigned long end)
> {
> - return htab_bolt_mapping(start, end, __pa(start),
> - pgprot_val(PAGE_KERNEL), mmu_linear_psize,
> - mmu_kernel_ssize);
> + int rc = htab_bolt_mapping(start, end, __pa(start),
> + pgprot_val(PAGE_KERNEL), mmu_linear_psize,
> + mmu_kernel_ssize);
> +
> + if (rc < 0) {
> + int rc2 = htab_remove_mapping(start, end, mmu_linear_psize,
> + mmu_kernel_ssize);
> + BUG_ON(rc2 && (rc2 != -ENOENT));
> + }
> + return rc;
> }
>
> int remove_section_mapping(unsigned long start, unsigned long end)
> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index baa1a23..fbc9448 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -188,9 +188,9 @@ static int __meminit vmemmap_populated(unsigned long start, int page_size)
> */
>
> #ifdef CONFIG_PPC_BOOK3E
> -static void __meminit vmemmap_create_mapping(unsigned long start,
> - unsigned long page_size,
> - unsigned long phys)
> +static int __meminit vmemmap_create_mapping(unsigned long start,
> + unsigned long page_size,
> + unsigned long phys)
> {
> /* Create a PTE encoding without page size */
> unsigned long i, flags = _PAGE_PRESENT | _PAGE_ACCESSED |
> @@ -208,6 +208,8 @@ static void __meminit vmemmap_create_mapping(unsigned long start,
> */
> for (i = 0; i < page_size; i += PAGE_SIZE)
> BUG_ON(map_kernel_page(start + i, phys, flags));
> +
> + return 0;
> }
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> @@ -217,15 +219,20 @@ static void vmemmap_remove_mapping(unsigned long start,
> }
> #endif
> #else /* CONFIG_PPC_BOOK3E */
> -static void __meminit vmemmap_create_mapping(unsigned long start,
> - unsigned long page_size,
> - unsigned long phys)
> +static int __meminit vmemmap_create_mapping(unsigned long start,
> + unsigned long page_size,
> + unsigned long phys)
> {
> - int mapped = htab_bolt_mapping(start, start + page_size, phys,
> - pgprot_val(PAGE_KERNEL),
> - mmu_vmemmap_psize,
> - mmu_kernel_ssize);
> - BUG_ON(mapped < 0);
> + int rc = htab_bolt_mapping(start, start + page_size, phys,
> + pgprot_val(PAGE_KERNEL),
> + mmu_vmemmap_psize, mmu_kernel_ssize);
> + if (rc < 0) {
> + int rc2 = htab_remove_mapping(start, start + page_size,
> + mmu_vmemmap_psize,
> + mmu_kernel_ssize);
> + BUG_ON(rc2 && (rc2 != -ENOENT));
> + }
> + return rc;
> }
>
> #ifdef CONFIG_MEMORY_HOTPLUG
> @@ -304,6 +311,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
>
> for (; start < end; start += page_size) {
> void *p;
> + int rc;
>
> if (vmemmap_populated(start, page_size))
> continue;
> @@ -317,7 +325,13 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
> pr_debug(" * %016lx..%016lx allocated at %p\n",
> start, start + page_size, p);
>
> - vmemmap_create_mapping(start, page_size, __pa(p));
> + rc = vmemmap_create_mapping(start, page_size, __pa(p));
> + if (rc < 0) {
> + pr_warning(
> + "vmemmap_populate: Unable to create vmemmap mapping: %d\n",
> + rc);
> + return -EFAULT;
> + }
> }
>
> return 0;
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index d0f0a51..f980da6 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -119,12 +119,18 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
> struct zone *zone;
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
> + int rc;
>
> pgdata = NODE_DATA(nid);
>
> start = (unsigned long)__va(start);
> - if (create_section_mapping(start, start + size))
> - return -EINVAL;
> + rc = create_section_mapping(start, start + size);
> + if (rc) {
> + pr_warning(
> + "Unable to create mapping for hot added memory 0x%llx..0x%llx: %d\n",
> + start, start + size, rc);
> + return -EFAULT;
> + }
>
> /* this should work for most non-highmem platforms */
> zone = pgdata->node_zones +
> --
> 2.5.0
>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@...ts.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
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