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Date: Sun, 25 Mar 2012 06:37:48 -0400
From: Kautuk Consul <consul.kautuk@...il.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: linux-m68k@...ts.linux-m68k.org, linux-arch@...r.kernel.org,
linux-kernel@...r.kernel.org,
Kautuk Consul <consul.kautuk@...il.com>
Subject: [PATCH 08/20 v3] m68k/mm/fault.c: Port OOM changes to do_page_fault
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 m68k.
Signed-off-by: Kautuk Consul <consul.kautuk@...il.com>
---
arch/m68k/mm/fault.c | 42 ++++++++++++++++++++++++++++++++++--------
1 files changed, 34 insertions(+), 8 deletions(-)
diff --git a/arch/m68k/mm/fault.c b/arch/m68k/mm/fault.c
index 2db6099..fc5b8c9 100644
--- a/arch/m68k/mm/fault.c
+++ b/arch/m68k/mm/fault.c
@@ -73,7 +73,8 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
{
struct mm_struct *mm = current->mm;
struct vm_area_struct * vma;
- int write, fault;
+ int fault;
+ unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
#ifdef DEBUG
printk ("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
@@ -88,6 +89,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
if (in_atomic() || !mm)
goto no_context;
+retry:
down_read(&mm->mmap_sem);
vma = find_vma(mm, address);
@@ -118,14 +120,13 @@ good_area:
#ifdef DEBUG
printk("do_page_fault: good_area\n");
#endif
- write = 0;
switch (error_code & 3) {
default: /* 3: write, present */
/* fall through */
case 2: /* write, not present */
if (!(vma->vm_flags & VM_WRITE))
goto acc_err;
- write++;
+ flags |= FAULT_FLAG_WRITE;
break;
case 1: /* read, present */
goto acc_err;
@@ -140,10 +141,14 @@ good_area:
* the fault.
*/
- fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0);
+ fault = handle_mm_fault(mm, vma, address, flags);
#ifdef DEBUG
printk("handle_mm_fault returns %d\n",fault);
#endif
+
+ if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+ return 0;
+
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM)
goto out_of_memory;
@@ -151,10 +156,31 @@ good_area:
goto bus_err;
BUG();
}
- if (fault & VM_FAULT_MAJOR)
- current->maj_flt++;
- else
- current->min_flt++;
+
+ /*
+ * Major/minor page fault accounting is only done on the
+ * initial attempt. If we go through a retry, it is extremely
+ * likely that the page will be found in page cache at that point.
+ */
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ if (fault & VM_FAULT_MAJOR)
+ current->maj_flt++;
+ else
+ current->min_flt++;
+ if (fault & VM_FAULT_RETRY) {
+ /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
+ * of starvation. */
+ 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);
return 0;
--
1.7.5.4
--
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