[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>

diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index 02d29c2..8443daf 100644 (file)
--- 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;