alpha/mm/fault.c: Port OOM changes to do_page_fault

Commit 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 ALPHA.

Signed-off-by: Mohd. Faris <mohdfarisq2010@gmail.com>
Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Acked-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 30 insertions, 6 deletions

diff --git a/arch/alpha/mm/fault.c b/arch/alpha/mm/fault.c
index 5eecab1a84ef..0c4132dd3507 100644
--- a/arch/alpha/mm/fault.c
+++ b/arch/alpha/mm/fault.c
@@ -89,6 +89,8 @@ do_page_fault(unsigned long address, unsigned long mmcsr,
         const struct exception_table_entry *fixup;
         int fault, si_code = SEGV_MAPERR;
         siginfo_t info;
+        unsigned int flags = (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+                              (cause > 0 ? FAULT_FLAG_WRITE : 0));
 
         /* As of EV6, a load into $31/$f31 is a prefetch, and never faults
            (or is suppressed by the PALcode).  Support that for older CPUs
@@ -114,6 +116,7 @@ do_page_fault(unsigned long address, unsigned long mmcsr,
                 goto vmalloc_fault;
 #endif
 
+retry:
         down_read(&mm->mmap_sem);
         vma = find_vma(mm, address);
         if (!vma)
@@ -144,8 +147,11 @@ do_page_fault(unsigned long address, unsigned long mmcsr,
         /* If for any reason at all we couldn't handle the fault,
            make sure we exit gracefully rather than endlessly redo
            the fault.  */
-        fault = handle_mm_fault(mm, vma, address, cause > 0 ? FAULT_FLAG_WRITE : 0);
-        up_read(&mm->mmap_sem);
+        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;
@@ -153,10 +159,26 @@ do_page_fault(unsigned long address, unsigned long mmcsr,
                         goto do_sigbus;
                 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;
 
         /* Something tried to access memory that isn't in our memory map.
@@ -186,12 +208,14 @@ do_page_fault(unsigned long address, unsigned long mmcsr,
         /* We ran out of memory, or some other thing happened to us that
            made us unable to handle the page fault gracefully.  */
  out_of_memory:
+        up_read(&mm->mmap_sem);
         if (!user_mode(regs))
                 goto no_context;
         pagefault_out_of_memory();
         return;
 
  do_sigbus:
+        up_read(&mm->mmap_sem);
         /* Send a sigbus, regardless of whether we were in kernel
            or user mode.  */
         info.si_signo = SIGBUS;