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Subject[PATCH 17/20] sh/mm/fault_32.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 the 32-bit SH platform.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
---
arch/sh/mm/fault_32.c | 39 ++++++++++++++++++++++++++++++---------
1 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/arch/sh/mm/fault_32.c b/arch/sh/mm/fault_32.c
index 7bebd04..7b279a7 100644
--- a/arch/sh/mm/fault_32.c
+++ b/arch/sh/mm/fault_32.c
@@ -129,6 +129,8 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
int si_code;
int fault;
siginfo_t info;
+ unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+ (writeaccess ? FAULT_FLAG_WRITE : 0);

tsk = current;
mm = tsk->mm;
@@ -169,6 +171,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
if (in_atomic() || !mm)
goto no_context;

+retry:
down_read(&mm->mmap_sem);

vma = find_vma(mm, address);
@@ -200,7 +203,11 @@ good_area:
* make sure we exit gracefully rather than endlessly redo
* the fault.
*/
- fault = handle_mm_fault(mm, vma, address, writeaccess ? 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;
@@ -208,14 +215,28 @@ good_area:
goto do_sigbus;
BUG();
}
- if (fault & VM_FAULT_MAJOR) {
- tsk->maj_flt++;
- perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
- regs, address);
- } else {
- tsk->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) {
+ tsk->maj_flt++;
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
+ regs, address);
+ } else {
+ tsk->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


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