[PATCH 04/20 v3] powerpc/mm/fault.c: Port OOM changes to do_page_fault

[PATCH 04/20 v3] powerpc/mm/fault.c: Port OOM changes to do_page_fault

[Kautuk Consul]

Commit d065bd810b6deb67d4897a14bfe21f8eb526ba99
(mm: retry page fault when blocking on disk transfer) and
commit 37b23e0525d393d48a7d59f870b3bc061a30ccdb
(x86,mm: make pagefault killable)

The above commits introduced changes into the x86 pagefault handler
for making the page fault handler retryable as well as killable.

These changes reduce the mmap_sem hold time, which is crucial
during OOM killer invocation.

Port these changes to powerpc.

Signed-off-by: Mohd. Faris <mohdfarisq2010@gmail.com>
Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
---
 arch/powerpc/mm/fault.c |   51 +++++++++++++++++++++++++++++++++-------------
 1 files changed, 36 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 2f0d1b0..a3b1176 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -129,6 +129,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
 	int is_write = 0, ret;
 	int trap = TRAP(regs);
  	int is_exec = trap == 0x400;
+	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
 	/*
@@ -212,6 +213,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
 		if (!user_mode(regs) && !search_exception_tables(regs->nip))
 			goto bad_area_nosemaphore;
 
+retry:
 		down_read(&mm->mmap_sem);
 	}
 
@@ -313,6 +315,7 @@ good_area:
 	} else if (is_write) {
 		if (!(vma->vm_flags & VM_WRITE))
 			goto bad_area;
+		flags |= FAULT_FLAG_WRITE;
 	/* a read */
 	} else {
 		/* protection fault */
@@ -327,7 +330,11 @@ good_area:
 	 * make sure we exit gracefully rather than endlessly redo
 	 * the fault.
 	 */
-	ret = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
+	ret = handle_mm_fault(mm, vma, address, flags);
+
+	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+		return 0;
+
 	if (unlikely(ret & VM_FAULT_ERROR)) {
 		if (ret & VM_FAULT_OOM)
 			goto out_of_memory;
@@ -335,22 +342,36 @@ good_area:
 			goto do_sigbus;
 		BUG();
 	}
-	if (ret & VM_FAULT_MAJOR) {
-		current->maj_flt++;
-		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
-				     regs, address);
-#ifdef CONFIG_PPC_SMLPAR
-		if (firmware_has_feature(FW_FEATURE_CMO)) {
-			preempt_disable();
-			get_lppaca()->page_ins += (1 << PAGE_FACTOR);
-			preempt_enable();
+	if (flags & FAULT_FLAG_ALLOW_RETRY) {
+		if (ret & VM_FAULT_MAJOR) {
+			current->maj_flt++;
+			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
+					     regs, address);
+#ifdef CONFIG_PPC_SMLPAR
+			if (firmware_has_feature(FW_FEATURE_CMO)) {
+				preempt_disable();
+				get_lppaca()->page_ins += (1 << PAGE_FACTOR);
+				preempt_enable();
+			}
+#endif
+		} else {
+			current->min_flt++;
+			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
+					     regs, address);
+		}
+		if (fault & VM_FAULT_RETRY) {
+			flags &= ~FAULT_FLAG_ALLOW_RETRY;
+
+			/*
+			 * No need to up_read(&mm->mmap_sem) as we would
+			 * have already released it in __lock_page_or_retry
+			 * in mm/filemap.c.
+			 */
+
+			goto retry;
 		}
-#endif
-	} else {
-		current->min_flt++;
-		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
-				     regs, address);
 	}
+
 	up_read(&mm->mmap_sem);
 	return 0;
 
-- 
1.7.5.4

Re: [PATCH 04/20 v3] powerpc/mm/fault.c: Port OOM changes to do_page_fault

[Benjamin Herrenschmidt]

On Tue, 2012-03-20 at 12:01 -0400, Kautuk Consul wrote:
> Commit d065bd810b6deb67d4897a14bfe21f8eb526ba99
> (mm: retry page fault when blocking on disk transfer) and
> commit 37b23e0525d393d48a7d59f870b3bc061a30ccdb
> (x86,mm: make pagefault killable)
> 
> The above commits introduced changes into the x86 pagefault handler
> for making the page fault handler retryable as well as killable.
> 
> These changes reduce the mmap_sem hold time, which is crucial
> during OOM killer invocation.
> 
> Port these changes to powerpc.

I have done that port already :-) It's in powerpc-next which I will send
to Linus to pull today or tomorrow....

Cheers,
Ben.

> Signed-off-by: Mohd. Faris <mohdfarisq2010@gmail.com>
> Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
> ---
>  arch/powerpc/mm/fault.c |   51 +++++++++++++++++++++++++++++++++-------------
>  1 files changed, 36 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 2f0d1b0..a3b1176 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -129,6 +129,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
>  	int is_write = 0, ret;
>  	int trap = TRAP(regs);
>   	int is_exec = trap == 0x400;
> +	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
>  
>  #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
>  	/*
> @@ -212,6 +213,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
>  		if (!user_mode(regs) && !search_exception_tables(regs->nip))
>  			goto bad_area_nosemaphore;
>  
> +retry:
>  		down_read(&mm->mmap_sem);
>  	}
>  
> @@ -313,6 +315,7 @@ good_area:
>  	} else if (is_write) {
>  		if (!(vma->vm_flags & VM_WRITE))
>  			goto bad_area;
> +		flags |= FAULT_FLAG_WRITE;
>  	/* a read */
>  	} else {
>  		/* protection fault */
> @@ -327,7 +330,11 @@ good_area:
>  	 * make sure we exit gracefully rather than endlessly redo
>  	 * the fault.
>  	 */
> -	ret = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
> +	ret = handle_mm_fault(mm, vma, address, flags);
> +
> +	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
> +		return 0;
> +
>  	if (unlikely(ret & VM_FAULT_ERROR)) {
>  		if (ret & VM_FAULT_OOM)
>  			goto out_of_memory;
> @@ -335,22 +342,36 @@ good_area:
>  			goto do_sigbus;
>  		BUG();
>  	}
> -	if (ret & VM_FAULT_MAJOR) {
> -		current->maj_flt++;
> -		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
> -				     regs, address);
> -#ifdef CONFIG_PPC_SMLPAR
> -		if (firmware_has_feature(FW_FEATURE_CMO)) {
> -			preempt_disable();
> -			get_lppaca()->page_ins += (1 << PAGE_FACTOR);
> -			preempt_enable();
> +	if (flags & FAULT_FLAG_ALLOW_RETRY) {
> +		if (ret & VM_FAULT_MAJOR) {
> +			current->maj_flt++;
> +			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
> +					     regs, address);
> +#ifdef CONFIG_PPC_SMLPAR
> +			if (firmware_has_feature(FW_FEATURE_CMO)) {
> +				preempt_disable();
> +				get_lppaca()->page_ins += (1 << PAGE_FACTOR);
> +				preempt_enable();
> +			}
> +#endif
> +		} else {
> +			current->min_flt++;
> +			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
> +					     regs, address);
> +		}
> +		if (fault & VM_FAULT_RETRY) {
> +			flags &= ~FAULT_FLAG_ALLOW_RETRY;
> +
> +			/*
> +			 * No need to up_read(&mm->mmap_sem) as we would
> +			 * have already released it in __lock_page_or_retry
> +			 * in mm/filemap.c.
> +			 */
> +
> +			goto retry;
>  		}
> -#endif
> -	} else {
> -		current->min_flt++;
> -		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
> -				     regs, address);
>  	}
> +
>  	up_read(&mm->mmap_sem);
>  	return 0;
>  

Re: [PATCH 04/20 v3] powerpc/mm/fault.c: Port OOM changes to do_page_fault

[Benjamin Herrenschmidt]

On Wed, 2012-03-21 at 08:28 +1100, Benjamin Herrenschmidt wrote:
> On Tue, 2012-03-20 at 12:01 -0400, Kautuk Consul wrote:
> > Commit d065bd810b6deb67d4897a14bfe21f8eb526ba99
> > (mm: retry page fault when blocking on disk transfer) and
> > commit 37b23e0525d393d48a7d59f870b3bc061a30ccdb
> > (x86,mm: make pagefault killable)
> > 
> > The above commits introduced changes into the x86 pagefault handler
> > for making the page fault handler retryable as well as killable.
> > 
> > These changes reduce the mmap_sem hold time, which is crucial
> > during OOM killer invocation.
> > 
> > Port these changes to powerpc.
> 
> I have done that port already :-) It's in powerpc-next which I will send
> to Linus to pull today or tomorrow....

BTW. Feel free to review what I've done, it's quite possible that I have
screwed something up ...

Cheers,
Ben.

> Cheers,
> Ben.
> 
> > Signed-off-by: Mohd. Faris <mohdfarisq2010@gmail.com>
> > Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
> > ---
> >  arch/powerpc/mm/fault.c |   51 +++++++++++++++++++++++++++++++++-------------
> >  1 files changed, 36 insertions(+), 15 deletions(-)
> > 
> > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> > index 2f0d1b0..a3b1176 100644
> > --- a/arch/powerpc/mm/fault.c
> > +++ b/arch/powerpc/mm/fault.c
> > @@ -129,6 +129,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
> >  	int is_write = 0, ret;
> >  	int trap = TRAP(regs);
> >   	int is_exec = trap == 0x400;
> > +	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
> >  
> >  #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
> >  	/*
> > @@ -212,6 +213,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
> >  		if (!user_mode(regs) && !search_exception_tables(regs->nip))
> >  			goto bad_area_nosemaphore;
> >  
> > +retry:
> >  		down_read(&mm->mmap_sem);
> >  	}
> >  
> > @@ -313,6 +315,7 @@ good_area:
> >  	} else if (is_write) {
> >  		if (!(vma->vm_flags & VM_WRITE))
> >  			goto bad_area;
> > +		flags |= FAULT_FLAG_WRITE;
> >  	/* a read */
> >  	} else {
> >  		/* protection fault */
> > @@ -327,7 +330,11 @@ good_area:
> >  	 * make sure we exit gracefully rather than endlessly redo
> >  	 * the fault.
> >  	 */
> > -	ret = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
> > +	ret = handle_mm_fault(mm, vma, address, flags);
> > +
> > +	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
> > +		return 0;
> > +
> >  	if (unlikely(ret & VM_FAULT_ERROR)) {
> >  		if (ret & VM_FAULT_OOM)
> >  			goto out_of_memory;
> > @@ -335,22 +342,36 @@ good_area:
> >  			goto do_sigbus;
> >  		BUG();
> >  	}
> > -	if (ret & VM_FAULT_MAJOR) {
> > -		current->maj_flt++;
> > -		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
> > -				     regs, address);
> > -#ifdef CONFIG_PPC_SMLPAR
> > -		if (firmware_has_feature(FW_FEATURE_CMO)) {
> > -			preempt_disable();
> > -			get_lppaca()->page_ins += (1 << PAGE_FACTOR);
> > -			preempt_enable();
> > +	if (flags & FAULT_FLAG_ALLOW_RETRY) {
> > +		if (ret & VM_FAULT_MAJOR) {
> > +			current->maj_flt++;
> > +			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
> > +					     regs, address);
> > +#ifdef CONFIG_PPC_SMLPAR
> > +			if (firmware_has_feature(FW_FEATURE_CMO)) {
> > +				preempt_disable();
> > +				get_lppaca()->page_ins += (1 << PAGE_FACTOR);
> > +				preempt_enable();
> > +			}
> > +#endif
> > +		} else {
> > +			current->min_flt++;
> > +			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
> > +					     regs, address);
> > +		}
> > +		if (fault & VM_FAULT_RETRY) {
> > +			flags &= ~FAULT_FLAG_ALLOW_RETRY;
> > +
> > +			/*
> > +			 * No need to up_read(&mm->mmap_sem) as we would
> > +			 * have already released it in __lock_page_or_retry
> > +			 * in mm/filemap.c.
> > +			 */
> > +
> > +			goto retry;
> >  		}
> > -#endif
> > -	} else {
> > -		current->min_flt++;
> > -		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
> > -				     regs, address);
> >  	}
> > +
> >  	up_read(&mm->mmap_sem);
> >  	return 0;
> >  
> 

Re: [PATCH 04/20 v3] powerpc/mm/fault.c: Port OOM changes to do_page_fault

[Kautuk Consul]

>>
>> I have done that port already :-) It's in powerpc-next which I will send
>> to Linus to pull today or tomorrow....

Oops, sorry I didn't know that as I don't regularly follow the powerpc tree.
I just did this change for all architectures. :)

>
> BTW. Feel free to review what I've done, it's quite possible that I have
> screwed something up ...

Okay, I'll take a look at it. Thanks again. :)

>
> Cheers,
> Ben.