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[Patch v4] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

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  [Patch v4] Do not reserve crashkernel high memory if crashkernel low memory reserving failed Baoquan He <bhe@redhat.com> - 2015-09-22 13:50 +0200
    Re: [Patch v4] Do not reserve crashkernel high memory if crashkernel  low memory reserving failed Baoquan He <bhe@redhat.com> - 2015-09-22 16:00 +0200
    Re: [Patch v4] Do not reserve crashkernel high memory if  crashkernel low memory reserving failed Andrew Morton <akpm@linux-foundation.org> - 2015-09-22 22:00 +0200
      Re: [Patch v4] Do not reserve crashkernel high memory if crashkernel  low memory reserving failed Baoquan He <bhe@redhat.com> - 2015-09-23 02:10 +0200
        Re: [Patch v4] Do not reserve crashkernel high memory if  crashkernel low memory reserving failed Andrew Morton <akpm@linux-foundation.org> - 2015-09-23 02:10 +0200
          Re: [Patch v4] Do not reserve crashkernel high memory if crashkernel  low memory reserving failed Baoquan He <bhe@redhat.com> - 2015-09-23 02:30 +0200

#1230098 — [Patch v4] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

People reported that when allocating crashkernel memory using
",high" and ",low" syntax, there were cases where the reservation
of the "high" portion succeeds, but the reservation of the "low"
portion fails. Then kexec can load kdump kernel successfully, but
the boot of kdump kernel fails as there's no low memory. This is
because allocation of low memory for kdump kernel can fail on large
systems for reasons. E.g it could be manually specified crashkernel
low memory is too large to find in memblock region.

In this patch add return value for reserve_crashkernel_low. Then
try to reserve crashkernel low memory after crashkernel high memory
has been allocated. If crashkernel low memory reservation failed
free crashkernel high memory and return. User can take measures
when they found kdump kernel cann't be loaded successfully.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
v1->v2:
  Boris commented that error value EINVAL is negative, should
  use "return -EINVAL".

v2->v3:
  Yinghai pointed out that during memblock_reserve, we could double
  the memblock reserve array. New memblock reserve could be overlapped
  with range for crashkernel high. So we have to reserve crashkernel
  high firstly, then free it if crashkernel low memory allocation
  failed.

v3->v4:
  Dave suggested using "return -ENOMEM" when low memory reservation
  failed and printing failure message anyway.

 arch/x86/kernel/setup.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index fdb7f2a..e362f92 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -493,7 +493,7 @@ static void __init memblock_x86_reserve_range_setup_data(void)
 # define CRASH_KERNEL_ADDR_HIGH_MAX	MAXMEM
 #endif
 
-static void __init reserve_crashkernel_low(void)
+static int __init reserve_crashkernel_low(void)
 {
 #ifdef CONFIG_X86_64
 	const unsigned long long alignment = 16<<20;	/* 16M */
@@ -522,17 +522,15 @@ static void __init reserve_crashkernel_low(void)
 	} else {
 		/* passed with crashkernel=0,low ? */
 		if (!low_size)
-			return;
+			return 0;
 	}
 
 	low_base = memblock_find_in_range(low_size, (1ULL<<32),
 					low_size, alignment);
 
 	if (!low_base) {
-		if (!auto_set)
-			pr_info("crashkernel low reservation failed - No suitable area found.\n");
-
-		return;
+		pr_info("crashkernel low reservation failed - No suitable area found.\n");
+		return -ENOMEM;
 	}
 
 	memblock_reserve(low_base, low_size);
@@ -544,6 +542,7 @@ static void __init reserve_crashkernel_low(void)
 	crashk_low_res.end   = low_base + low_size - 1;
 	insert_resource(&iomem_resource, &crashk_low_res);
 #endif
+	return 0;
 }
 
 static void __init reserve_crashkernel(void)
@@ -595,6 +594,11 @@ static void __init reserve_crashkernel(void)
 	}
 	memblock_reserve(crash_base, crash_size);
 
+	if (crash_base >= (1ULL<<32) && reserve_crashkernel_low()) {
+		memblock_free(crash_base, crash_size);
+		return;
+	}
+
 	printk(KERN_INFO "Reserving %ldMB of memory at %ldMB "
 			"for crashkernel (System RAM: %ldMB)\n",
 			(unsigned long)(crash_size >> 20),
@@ -604,9 +608,6 @@ static void __init reserve_crashkernel(void)
 	crashk_res.start = crash_base;
 	crashk_res.end   = crash_base + crash_size - 1;
 	insert_resource(&iomem_resource, &crashk_res);
-
-	if (crash_base >= (1ULL<<32))
-		reserve_crashkernel_low();
 }
 #else
 static void __init reserve_crashkernel(void)
-- 
2.1.0

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#1230232 — Re: [Patch v4] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

Add Jerry to CC list. 

On 09/22/15 at 07:48pm, Baoquan He wrote:
> People reported that when allocating crashkernel memory using
> ",high" and ",low" syntax, there were cases where the reservation
> of the "high" portion succeeds, but the reservation of the "low"
> portion fails. Then kexec can load kdump kernel successfully, but
> the boot of kdump kernel fails as there's no low memory. This is
> because allocation of low memory for kdump kernel can fail on large
> systems for reasons. E.g it could be manually specified crashkernel
> low memory is too large to find in memblock region.
> 
> In this patch add return value for reserve_crashkernel_low. Then
> try to reserve crashkernel low memory after crashkernel high memory
> has been allocated. If crashkernel low memory reservation failed
> free crashkernel high memory and return. User can take measures
> when they found kdump kernel cann't be loaded successfully.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
> v1->v2:
>   Boris commented that error value EINVAL is negative, should
>   use "return -EINVAL".
> 
> v2->v3:
>   Yinghai pointed out that during memblock_reserve, we could double
>   the memblock reserve array. New memblock reserve could be overlapped
>   with range for crashkernel high. So we have to reserve crashkernel
>   high firstly, then free it if crashkernel low memory allocation
>   failed.
> 
> v3->v4:
>   Dave suggested using "return -ENOMEM" when low memory reservation
>   failed and printing failure message anyway.
> 
>  arch/x86/kernel/setup.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index fdb7f2a..e362f92 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -493,7 +493,7 @@ static void __init memblock_x86_reserve_range_setup_data(void)
>  # define CRASH_KERNEL_ADDR_HIGH_MAX	MAXMEM
>  #endif
>  
> -static void __init reserve_crashkernel_low(void)
> +static int __init reserve_crashkernel_low(void)
>  {
>  #ifdef CONFIG_X86_64
>  	const unsigned long long alignment = 16<<20;	/* 16M */
> @@ -522,17 +522,15 @@ static void __init reserve_crashkernel_low(void)
>  	} else {
>  		/* passed with crashkernel=0,low ? */
>  		if (!low_size)
> -			return;
> +			return 0;
>  	}
>  
>  	low_base = memblock_find_in_range(low_size, (1ULL<<32),
>  					low_size, alignment);
>  
>  	if (!low_base) {
> -		if (!auto_set)
> -			pr_info("crashkernel low reservation failed - No suitable area found.\n");
> -
> -		return;
> +		pr_info("crashkernel low reservation failed - No suitable area found.\n");
> +		return -ENOMEM;
>  	}
>  
>  	memblock_reserve(low_base, low_size);
> @@ -544,6 +542,7 @@ static void __init reserve_crashkernel_low(void)
>  	crashk_low_res.end   = low_base + low_size - 1;
>  	insert_resource(&iomem_resource, &crashk_low_res);
>  #endif
> +	return 0;
>  }
>  
>  static void __init reserve_crashkernel(void)
> @@ -595,6 +594,11 @@ static void __init reserve_crashkernel(void)
>  	}
>  	memblock_reserve(crash_base, crash_size);
>  
> +	if (crash_base >= (1ULL<<32) && reserve_crashkernel_low()) {
> +		memblock_free(crash_base, crash_size);
> +		return;
> +	}
> +
>  	printk(KERN_INFO "Reserving %ldMB of memory at %ldMB "
>  			"for crashkernel (System RAM: %ldMB)\n",
>  			(unsigned long)(crash_size >> 20),
> @@ -604,9 +608,6 @@ static void __init reserve_crashkernel(void)
>  	crashk_res.start = crash_base;
>  	crashk_res.end   = crash_base + crash_size - 1;
>  	insert_resource(&iomem_resource, &crashk_res);
> -
> -	if (crash_base >= (1ULL<<32))
> -		reserve_crashkernel_low();
>  }
>  #else
>  static void __init reserve_crashkernel(void)
> -- 
> 2.1.0
> 
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#1230898 — Re: [Patch v4] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

On Tue, 22 Sep 2015 19:48:14 +0800 Baoquan He <bhe@redhat.com> wrote:

> People reported that when allocating crashkernel memory using
> ",high" and ",low" syntax, there were cases where the reservation
> of the "high" portion succeeds, but the reservation of the "low"
> portion fails. Then kexec can load kdump kernel successfully, but
> the boot of kdump kernel fails as there's no low memory. This is
> because allocation of low memory for kdump kernel can fail on large
> systems for reasons. E.g it could be manually specified crashkernel
> low memory is too large to find in memblock region.
> 
> In this patch add return value for reserve_crashkernel_low. Then
> try to reserve crashkernel low memory after crashkernel high memory
> has been allocated. If crashkernel low memory reservation failed
> free crashkernel high memory and return. User can take measures
> when they found kdump kernel cann't be loaded successfully.
>
> ...
>
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -493,7 +493,7 @@ static void __init memblock_x86_reserve_range_setup_data(void)
>  # define CRASH_KERNEL_ADDR_HIGH_MAX	MAXMEM
>  #endif
>  
> -static void __init reserve_crashkernel_low(void)
> +static int __init reserve_crashkernel_low(void)
>  {
>  #ifdef CONFIG_X86_64
>  	const unsigned long long alignment = 16<<20;	/* 16M */
> @@ -522,17 +522,15 @@ static void __init reserve_crashkernel_low(void)
>  	} else {
>  		/* passed with crashkernel=0,low ? */
>  		if (!low_size)
> -			return;
> +			return 0;

What's happening here?  It's returning "success" when
parse_crashkernel_low() fails?

>  	}
>  
>  	low_base = memblock_find_in_range(low_size, (1ULL<<32),
>  					low_size, alignment);
>  
>  	if (!low_base) {
> -		if (!auto_set)
> -			pr_info("crashkernel low reservation failed - No suitable area found.\n");
> -
> -		return;
> +		pr_info("crashkernel low reservation failed - No suitable area found.\n");

That's not a terribly useful message.  If kdump is now unavailable and
the operator needs to take some remedial action then we should inform
them of this.

Also, such a message should have higher severity than KERN_INFO?

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#1231055 — Re: [Patch v4] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

On 09/22/15 at 12:54pm, Andrew Morton wrote:
> > --- a/arch/x86/kernel/setup.c
> > +++ b/arch/x86/kernel/setup.c
> > @@ -493,7 +493,7 @@ static void __init memblock_x86_reserve_range_setup_data(void)
> >  # define CRASH_KERNEL_ADDR_HIGH_MAX	MAXMEM
> >  #endif
> >  
> > -static void __init reserve_crashkernel_low(void)
> > +static int __init reserve_crashkernel_low(void)
> >  {
> >  #ifdef CONFIG_X86_64
> >  	const unsigned long long alignment = 16<<20;	/* 16M */
> > @@ -522,17 +522,15 @@ static void __init reserve_crashkernel_low(void)
> >  	} else {
> >  		/* passed with crashkernel=0,low ? */
> >  		if (!low_size)
> > -			return;
> > +			return 0;
> 
> What's happening here?  It's returning "success" when
> parse_crashkernel_low() fails?

It's the case user specify "crashkernel=0,low" to disable
crashkernel low memory allocation explicitly. So here we parse the
cmdline and get it's in this case, reture 0 directly.

> 
> >  	}
> >  
> >  	low_base = memblock_find_in_range(low_size, (1ULL<<32),
> >  					low_size, alignment);
> >  
> >  	if (!low_base) {
> > -		if (!auto_set)
> > -			pr_info("crashkernel low reservation failed - No suitable area found.\n");
> > -
> > -		return;
> > +		pr_info("crashkernel low reservation failed - No suitable area found.\n");
> 
> That's not a terribly useful message.  If kdump is now unavailable and
> the operator needs to take some remedial action then we should inform
> them of this.
> 
> Also, such a message should have higher severity than KERN_INFO?

Yes, how about KERN_ERR? It's an unexpected result from kdump side
though it doesn't harm the normal kernel.


> 
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#1231058 — Re: [Patch v4] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

On Wed, 23 Sep 2015 08:02:55 +0800 Baoquan He <bhe@redhat.com> wrote:

> > 
> > >  	}
> > >  
> > >  	low_base = memblock_find_in_range(low_size, (1ULL<<32),
> > >  					low_size, alignment);
> > >  
> > >  	if (!low_base) {
> > > -		if (!auto_set)
> > > -			pr_info("crashkernel low reservation failed - No suitable area found.\n");
> > > -
> > > -		return;
> > > +		pr_info("crashkernel low reservation failed - No suitable area found.\n");
> > 
> > That's not a terribly useful message.  If kdump is now unavailable and
> > the operator needs to take some remedial action then we should inform
> > them of this.
> > 
> > Also, such a message should have higher severity than KERN_INFO?
> 
> Yes, how about KERN_ERR? It's an unexpected result from kdump side
> though it doesn't harm the normal kernel.

Sure, KERN_ERR is good.  Along with more useful message text.
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#1231068 — Re: [Patch v4] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

On 09/22/15 at 05:08pm, Andrew Morton wrote:
> On Wed, 23 Sep 2015 08:02:55 +0800 Baoquan He <bhe@redhat.com> wrote:
> 
> > > 
> > > >  	}
> > > >  
> > > >  	low_base = memblock_find_in_range(low_size, (1ULL<<32),
> > > >  					low_size, alignment);
> > > >  
> > > >  	if (!low_base) {
> > > > -		if (!auto_set)
> > > > -			pr_info("crashkernel low reservation failed - No suitable area found.\n");
> > > > -
> > > > -		return;
> > > > +		pr_info("crashkernel low reservation failed - No suitable area found.\n");
> > > 
> > > That's not a terribly useful message.  If kdump is now unavailable and
> > > the operator needs to take some remedial action then we should inform
> > > them of this.
> > > 
> > > Also, such a message should have higher severity than KERN_INFO?
> > 
> > Yes, how about KERN_ERR? It's an unexpected result from kdump side
> > though it doesn't harm the normal kernel.
> 
> Sure, KERN_ERR is good.  Along with more useful message text.

OK, will do. Thanks for your suggestion.


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