sh/mm/fault_32.c: Port OOM changes to 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 the 32-bit SH platform.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

diff --git a/arch/sh/mm/fault_32.c b/arch/sh/mm/fault_32.c
index 324eef9..98e88a6 100644 (file)
--- a/arch/sh/mm/fault_32.c
+++ b/arch/sh/mm/fault_32.c
@@ -129,6 +129,8 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
        int si_code;
        int fault;
        siginfo_t info;
+       unsigned int flags = (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+                             (writeaccess ? FAULT_FLAG_WRITE : 0));
 
        tsk = current;
        mm = tsk->mm;
@@ -169,6 +171,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
        if (in_atomic() || !mm)
                goto no_context;
 
+retry:
        down_read(&mm->mmap_sem);
 
        vma = find_vma(mm, address);
@@ -200,7 +203,11 @@ good_area:
         * make sure we exit gracefully rather than endlessly redo
         * the fault.
         */
-       fault = handle_mm_fault(mm, vma, address, writeaccess ? 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)) {
                if (fault & VM_FAULT_OOM)
                        goto out_of_memory;
@@ -208,14 +215,27 @@ good_area:
                        goto do_sigbus;
                BUG();
        }
-       if (fault & VM_FAULT_MAJOR) {
-               tsk->maj_flt++;
-               perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
-                                    regs, address);
-       } else {
-               tsk->min_flt++;
-               perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
-                                    regs, address);
+
+       if (flags & FAULT_FLAG_ALLOW_RETRY) {
+               if (fault & VM_FAULT_MAJOR) {
+                       tsk->maj_flt++;
+                       perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
+                                     regs, address);
+               } else {
+                       tsk->min_flt++;
+                       perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
+                                     regs, address);
+               }
+               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);