openrisc/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 openrisc.

Signed-off-by: Mohd. Faris <mohdfarisq2010@gmail.com>
Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Signed-off-by: Jonas Bonn <jonas@southpole.se>

diff --git a/arch/openrisc/mm/fault.c b/arch/openrisc/mm/fault.c
index a5dce82f864b2d41f0a39a3daea998ba1938f069..40f850e9766c78a0d790a040937b2d053b8ac4bd 100644 (file)
--- a/arch/openrisc/mm/fault.c
+++ b/arch/openrisc/mm/fault.c
@@ -54,6 +54,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
        struct vm_area_struct *vma;
        siginfo_t info;
        int fault;
+       unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
        tsk = current;
 
@@ -105,6 +106,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address,
        if (in_interrupt() || !mm)
                goto no_context;
 
+retry:
        down_read(&mm->mmap_sem);
        vma = find_vma(mm, address);
 
@@ -143,6 +145,7 @@ good_area:
        if (write_acc) {
                if (!(vma->vm_flags & VM_WRITE))
                        goto bad_area;
+               flags |= FAULT_FLAG_WRITE;
        } else {
                /* not present */
                if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
@@ -159,7 +162,11 @@ good_area:
         * the fault.
         */
 
-       fault = handle_mm_fault(mm, vma, address, write_acc);
+       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;
@@ -167,11 +174,24 @@ good_area:
                        goto do_sigbus;
                BUG();
        }
-       /*RGD modeled on Cris */
-       if (fault & VM_FAULT_MAJOR)
-               tsk->maj_flt++;
-       else
-               tsk->min_flt++;
+
+       if (flags & FAULT_FLAG_ALLOW_RETRY) {
+               /*RGD modeled on Cris */
+               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;