[PATCH 20/20 v4] sparc/mm/fault_64.c: Port OOM changes to do_sparc64_fault

[PATCH 20/20 v4] sparc/mm/fault_64.c: Port OOM changes to do_sparc64_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 64-bit sparc.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
---
 arch/sparc/mm/fault_64.c |   37 ++++++++++++++++++++++++++++++-------
 1 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/arch/sparc/mm/fault_64.c b/arch/sparc/mm/fault_64.c
index 504c062..d8692e4 100644
--- a/arch/sparc/mm/fault_64.c
+++ b/arch/sparc/mm/fault_64.c
@@ -279,6 +279,7 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
 	unsigned int insn = 0;
 	int si_code, fault_code, fault;
 	unsigned long address, mm_rss;
+	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
 	fault_code = get_thread_fault_code();
 
@@ -333,6 +334,8 @@ asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
 			insn = get_fault_insn(regs, insn);
 			goto handle_kernel_fault;
 		}
+
+retry:
 		down_read(&mm->mmap_sem);
 	}
 
@@ -423,7 +426,12 @@ good_area:
 			goto bad_area;
 	}
 
-	fault = handle_mm_fault(mm, vma, address, (fault_code & FAULT_CODE_WRITE) ? FAULT_FLAG_WRITE : 0);
+	flags |= ((fault_code & FAULT_CODE_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;
@@ -431,12 +439,27 @@ 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);
 
-- 
1.7.5.4

Re: [PATCH 20/20 v4] sparc/mm/fault_64.c: Port OOM changes to do_sparc64_fault

[David Miller]

From: Kautuk Consul <consul.kautuk@gmail.com>
Date: Mon, 26 Mar 2012 12:40:49 -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 64-bit sparc.
> 
> Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>

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

Re: [PATCH 20/20 v4] sparc/mm/fault_64.c: Port OOM changes to do_sparc64_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 12:40:49 -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 64-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 !