[PATCH 20/20 v2] sparc/mm/fault_64.c: Port OOM changes to do_sparc64_fault

[PATCH 20/20 v2] 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..e6da8ca 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);
+	fault = handle_mm_fault(mm, vma, address,
+	flags | ((fault_code & FAULT_CODE_WRITE) ? FAULT_FLAG_WRITE : 0);
+
+	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 v2] sparc/mm/fault_64.c: Port OOM changes to do_sparc64_fault

[David Miller]

From: Kautuk Consul <consul.kautuk@gmail.com>
Date: Sun, 25 Mar 2012 13:59:08 -0400

> +			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
> +					1, regs, address);

Improperly indented still.

> +			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
> +					1, regs, address);

Likewise.

Re: [PATCH 20/20 v2] sparc/mm/fault_64.c: Port OOM changes to do_sparc64_fault

[Kautuk Consul]

On Sun, Mar 25, 2012 at 3:04 PM, David Miller <davem@davemloft.net> wrote:
> From: Kautuk Consul <consul.kautuk@gmail.com>
> Date: Sun, 25 Mar 2012 13:59:08 -0400
>
>> +                     perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
>> +                                     1, regs, address);
>
> Improperly indented still.
>
>> +                     perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
>> +                                     1, regs, address);
>
> Likewise.

I didn't understand what you were saying as I use gmaiil so I could not "see"
what you meant exactly.
I have sent a v3 for this.

Re: [PATCH 20/20 v2] 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 11:36:42 -0400

> I didn't understand what you were saying as I use gmaiil so I could
> not "see" what you meant exactly.

This is not an excuse.

You need to be able to communicate with developers properly, and this
means being able to properly formatted read pure ASCII text in their
emails.  Otherwise people who give you feedback are simply wasting
their time.

We're on V3 of these two sparc patches, which is proof of how much
you're wasting my time.