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>

diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
index 54f18fc25ed07ebab77fe0f0b6d0e51e3204aa1c..84ce7abbf5afb80c5d82648244349bf7d746a9c0 100644 (file)
--- 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()
        /*