avr32/mm/fault.c: port OOM changes to do_page_fault

Commits d065bd810b6d ("mm: retry page fault when blocking on disk
transfer") and 37b23e0525d3 ("x86,mm: make pagefault killable")
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 AVR32.

[akpm@linux-foundation.org: fix comment layout]
Signed-off-by: Mohd. Faris <mohdfarisq2010@gmail.com>
Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Acked-by: Havard Skinnemoen <hskinnemoen@gmail.com>
Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 25 insertions, 8 deletions

diff --git a/arch/avr32/mm/fault.c b/arch/avr32/mm/fault.c
index f7040a1e399f..b92e60958617 100644
--- a/arch/avr32/mm/fault.c
+++ b/arch/avr32/mm/fault.c
@@ -61,10 +61,10 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
         const struct exception_table_entry *fixup;
         unsigned long address;
         unsigned long page;
-        int writeaccess;
         long signr;
         int code;
         int fault;
+        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
         if (notify_page_fault(regs, ecr))
                 return;
@@ -86,6 +86,7 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
 
         local_irq_enable();
 
+retry:
         down_read(&mm->mmap_sem);
 
         vma = find_vma(mm, address);
@@ -104,7 +105,6 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
          */
 good_area:
         code = SEGV_ACCERR;
-        writeaccess = 0;
 
         switch (ecr) {
         case ECR_PROTECTION_X:
@@ -121,7 +121,7 @@ good_area:
         case ECR_TLB_MISS_W:
                 if (!(vma->vm_flags & VM_WRITE))
                         goto bad_area;
-                writeaccess = 1;
+                flags |= FAULT_FLAG_WRITE;
                 break;
         default:
                 panic("Unhandled case %lu in do_page_fault!", ecr);
@@ -132,7 +132,11 @@ good_area:
          * 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;
@@ -140,10 +144,23 @@ good_area:
                         goto do_sigbus;
                 BUG();
         }
-        if (fault & VM_FAULT_MAJOR)
-                tsk->maj_flt++;
-        else
-                tsk->min_flt++;
+
+        if (flags & FAULT_FLAG_ALLOW_RETRY) {
+                if (fault & VM_FAULT_MAJOR)
+                        tsk->maj_flt++;
+                else
+                        tsk->min_flt++;
+                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);
         return;