tile/mm/fault.c: Port OOM changes to handle_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 tile.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
[cmetcalf@tilera.com: initialize "flags" after "write" updated.]
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

1 files changed, 27 insertions, 5 deletions

diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
index 54f18fc25ed0..84ce7abbf5af 100644
--- a/arch/tile/mm/fault.c
+++ b/arch/tile/mm/fault.c
@@ -273,11 +273,15 @@ static int handle_page_fault(struct pt_regs *regs,
         int si_code;
         int is_kernel_mode;
         pgd_t *pgd;
+        unsigned int flags;
 
         /* on TILE, protection faults are always writes */
         if (!is_page_fault)
                 write = 1;
 
+        flags = (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+                 (write ? FAULT_FLAG_WRITE : 0));
+
         is_kernel_mode = (EX1_PL(regs->ex1) != USER_PL);
 
         tsk = validate_current();
@@ -382,6 +386,8 @@ static int handle_page_fault(struct pt_regs *regs,
                         vma = NULL;  /* happy compiler */
                         goto bad_area_nosemaphore;
                 }
+
+retry:
                 down_read(&mm->mmap_sem);
         }
 
@@ -429,7 +435,11 @@ good_area:
          * make sure we exit gracefully rather than endlessly redo
          * the fault.
          */
-        fault = handle_mm_fault(mm, vma, address, write);
+        fault = handle_mm_fault(mm, vma, address, flags);
+
+        if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+                return 0;
+
         if (unlikely(fault & VM_FAULT_ERROR)) {
                 if (fault & VM_FAULT_OOM)
                         goto out_of_memory;
@@ -437,10 +447,22 @@ 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;
+                }
+        }
 
 #if CHIP_HAS_TILE_DMA() || CHIP_HAS_SN_PROC()
         /*