linux-kernel - [PATCH 1/1] arm: fault.c: correct how the tsk->[maj|min]

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Date:	Tue, 20 Mar 2012 12:30:57 -0400
From:	Kautuk Consul <consul.kautuk@...il.com>
To:	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Ingo Molnar <mingo@...e.hu>, Will Deacon <will.deacon@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Kautuk Consul <consul.kautuk@...il.com>
Subject: [PATCH 1/1] arm: fault.c: correct how the tsk->[maj|min]_flt gets incremented

commit 8878a539ff19a43cf3729e7562cd528f490246ae was done by me
to make the page fault handler retryable as well as interruptible.

Due to this commit, there is a mistake in the way in which
tsk->[maj|min]_flt counter gets incremented for VM_FAULT_ERROR:
If VM_FAULT_ERROR is returned in the fault flags by handle_mm_fault,
then either maj_flt or min_flt will get incremented. This is wrong
as in the case of a VM_FAULT_ERROR we need to be skip ahead to the
error handling code in do_page_fault.

Added a check after the call to __do_page_fault() to check for
(fault & VM_FAULT_ERROR).

Signed-off-by: Kautuk Consul <consul.kautuk@...il.com>
---
 arch/arm/mm/fault.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index bb7eac3..ec8c88b 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -318,7 +318,7 @@ retry:
 	 */

 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
-	if (flags & FAULT_FLAG_ALLOW_RETRY) {
+	if (!(fault & VM_FAULT_ERROR) && (flags & FAULT_FLAG_ALLOW_RETRY)) {
 		if (fault & VM_FAULT_MAJOR) {
 			tsk->maj_flt++;
 			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
-- 
1.7.5.4

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