Re: [RFCv2 4/9] arch/powerpc: Clean up memory hotplug failure paths

[Paul Mackerras]

On Fri, Jan 29, 2016 at 04:23:58PM +1100, David Gibson wrote:
> 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.
> 
> Signed-off-by: David Gibson 

Reviewed-by: Paul Mackerras 
___
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev

Re: [RFCv2 4/9] arch/powerpc: Clean up memory hotplug failure paths

[David Gibson]

On Tue, Feb 02, 2016 at 09:04:23AM -0600, Nathan Fontenot wrote:
> On 01/28/2016 11:23 PM, David Gibson wrote:
> > 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.
> > 
> > Signed-off-by: David Gibson 
> > ---
> >  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 0737eae..e88a86e 100644
> > --- a/arch/powerpc/mm/hash_utils_64.c
> > +++ b/arch/powerpc/mm/hash_utils_64.c
> > @@ -635,9 +635,16 @@ 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;
> >  }
> >  
> 
> <-- snip -->
> 
> >  #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;
> >  }
> >  
> 
> If I'm reading this correctly it appears that create_section_mapping() and
> vmemmap_create_mapping() for !PPC_BOOK3E are identical. Any reason to not
> have one routine, perhaps just have vmemmap_create_mapping() just call
> create_section_mapping()?

Not really, apart from documenting what they're used for.  They're
both fairly trivial wrappers around htab_bolt_mapping().  I think
cleaning this up is outside the scope of this series though.

-- 
David Gibson| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson


signature.asc
Description: PGP signature
___
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev

Re: [RFCv2 4/9] arch/powerpc: Clean up memory hotplug failure paths

[Nathan Fontenot]

On 01/28/2016 11:23 PM, David Gibson wrote:
> 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.
> 
> Signed-off-by: David Gibson 
> ---
>  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 0737eae..e88a86e 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -635,9 +635,16 @@ 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;
>  }
>  

<-- snip -->

>  #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;
>  }
>  

If I'm reading this correctly it appears that create_section_mapping() and
vmemmap_create_mapping() for !PPC_BOOK3E are identical. Any reason to not
have one routine, perhaps just have vmemmap_create_mapping() just call
create_section_mapping()?

-Nathan

___
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev

Re: [RFCv2 4/9] arch/powerpc: Clean up memory hotplug failure paths

[Anshuman Khandual]

On 01/29/2016 10:53 AM, David Gibson wrote:
> 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.

Yeah this greatly improves graceful fall back when when memory mapping
failure happens at the last level during memory hotplug.

___
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev

[RFCv2 4/9] arch/powerpc: Clean up memory hotplug failure paths

[David Gibson]

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.

Signed-off-by: David Gibson 
---
 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 0737eae..e88a86e 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -635,9 +635,16 @@ 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