[IA64] Port OOM changes to ia64_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 ia64.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 34 insertions, 12 deletions

diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index 02d29c2a132a..8443daf4f515 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -72,6 +72,10 @@ mapped_kernel_page_is_present (unsigned long address)
         return pte_present(pte);
 }
 
+#       define VM_READ_BIT      0
+#       define VM_WRITE_BIT     1
+#       define VM_EXEC_BIT      2
+
 void __kprobes
 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
 {
@@ -81,6 +85,12 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
         struct siginfo si;
         unsigned long mask;
         int fault;
+        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+
+        mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
+                | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
+
+        flags |= ((mask & VM_WRITE) ? FAULT_FLAG_WRITE : 0);
 
         /* mmap_sem is performance critical.... */
         prefetchw(&mm->mmap_sem);
@@ -109,6 +119,7 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
         if (notify_page_fault(regs, TRAP_BRKPT))
                 return;
 
+retry:
         down_read(&mm->mmap_sem);
 
         vma = find_vma_prev(mm, address, &prev_vma);
@@ -130,10 +141,6 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
 
         /* OK, we've got a good vm_area for this memory area.  Check the access permissions: */
 
-#       define VM_READ_BIT      0
-#       define VM_WRITE_BIT     1
-#       define VM_EXEC_BIT      2
-
 #       if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
             || (1 << VM_EXEC_BIT) != VM_EXEC)
 #               error File is out of sync with <linux/mm.h>.  Please update.
@@ -142,9 +149,6 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
         if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
                 goto bad_area;
 
-        mask = (  (((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
-                | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
-
         if ((vma->vm_flags & mask) != mask)
                 goto bad_area;
 
@@ -153,7 +157,11 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
          * sure we exit gracefully rather than endlessly redo the
          * fault.
          */
-        fault = handle_mm_fault(mm, vma, address, (mask & VM_WRITE) ? 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)) {
                 /*
                  * We ran out of memory, or some other thing happened
@@ -168,10 +176,24 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
                 }
                 BUG();
         }
-        if (fault & VM_FAULT_MAJOR)
-                current->maj_flt++;
-        else
-                current->min_flt++;
+
+        if (flags & FAULT_FLAG_ALLOW_RETRY) {
+                if (fault & VM_FAULT_MAJOR)
+                        current->maj_flt++;
+                else
+                        current->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;