[PATCH 19/20 v4] sparc/mm/fault_32.c: Port OOM changes to do_sparc_fault

[PATCH 19/20 v4] sparc/mm/fault_32.c: Port OOM changes to do_sparc_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 32-bit sparc.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
---
 arch/sparc/mm/fault_32.c |   37 ++++++++++++++++++++++++++++++-------
 1 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/arch/sparc/mm/fault_32.c b/arch/sparc/mm/fault_32.c
index 8023fd7..6da1818 100644
--- a/arch/sparc/mm/fault_32.c
+++ b/arch/sparc/mm/fault_32.c
@@ -226,6 +226,8 @@ asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
 	unsigned long g2;
 	int from_user = !(regs->psr & PSR_PS);
 	int fault, code;
+	unsigned int flags = (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+			      (write ? FAULT_FLAG_WRITE : 0));
 
 	if(text_fault)
 		address = regs->pc;
@@ -252,6 +254,7 @@ asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
+retry:
 	down_read(&mm->mmap_sem);
 
 	/*
@@ -290,7 +293,11 @@ good_area:
 	 * make sure we exit gracefully rather than endlessly redo
 	 * the fault.
 	 */
-	fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0);
+	fault = handle_mm_fault(mm, vma, address, flags);
+
+	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+		return;
+
 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		if (fault & VM_FAULT_OOM)
 			goto out_of_memory;
@@ -298,13 +305,29 @@ good_area:
 			goto do_sigbus;
 		BUG();
 	}
-	if (fault & VM_FAULT_MAJOR) {
-		current->maj_flt++;
-		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
-	} else {
-		current->min_flt++;
-		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
+
+	if (flags & FAULT_FLAG_ALLOW_RETRY) {
+		if (fault & VM_FAULT_MAJOR) {
+			current->maj_flt++;
+			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
+				      1, regs, address);
+		} 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;
+		}
 	}
+
 	up_read(&mm->mmap_sem);
 	return;
 
-- 
1.7.5.4

Re: [PATCH 19/20 v4] sparc/mm/fault_32.c: Port OOM changes to do_sparc_fault

[David Miller]

From: Kautuk Consul <consul.kautuk@gmail.com>
Date: Mon, 26 Mar 2012 12:47:54 -0400

> 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 32-bit sparc.
> 
> Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>

Acked-by: David S. Miller <davem@davemloft.net>

Re: [PATCH 19/20 v4] sparc/mm/fault_32.c: Port OOM changes to do_sparc_fault

[Kautuk Consul]

On Tue, Mar 27, 2012 at 3:06 AM, David Miller <davem@davemloft.net> wrote:
> From: Kautuk Consul <consul.kautuk@gmail.com>
> Date: Mon, 26 Mar 2012 12:47:54 -0400
>
>> 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 32-bit sparc.
>>
>> Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
>
> Acked-by: David S. Miller <davem@davemloft.net>

Thanks David.

Since one or two of my other patches are being taken by the other arch
owners in their branches,
can you take this patch and apply it to your branch also ?

Much obliged if you do !

Re: [PATCH 19/20 v4] sparc/mm/fault_32.c: Port OOM changes to do_sparc_fault

[David Miller]

From: Kautuk Consul <consul.kautuk@gmail.com>
Date: Wed, 4 Apr 2012 20:00:01 +0530

> Since one or two of my other patches are being taken by the other arch
> owners in their branches,
> can you take this patch and apply it to your branch also ?

Both sparc patches applied, thanks.