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


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