[S390] mm: add page fault retry handling
s390 arch backend for d065bd81 "mm: retry page fault when blocking on
disk transfer".
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index b57723a..fe103e8 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -280,7 +280,8 @@
struct mm_struct *mm;
struct vm_area_struct *vma;
unsigned long address;
- int fault, write;
+ unsigned int flags;
+ int fault;
if (notify_page_fault(regs))
return 0;
@@ -299,6 +300,10 @@
address = trans_exc_code & __FAIL_ADDR_MASK;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address);
+ flags = FAULT_FLAG_ALLOW_RETRY;
+ if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400)
+ flags |= FAULT_FLAG_WRITE;
+retry:
down_read(&mm->mmap_sem);
fault = VM_FAULT_BADMAP;
@@ -328,21 +333,31 @@
* make sure we exit gracefully rather than endlessly redo
* the fault.
*/
- write = (access == VM_WRITE ||
- (trans_exc_code & store_indication) == 0x400) ?
- FAULT_FLAG_WRITE : 0;
- fault = handle_mm_fault(mm, vma, address, write);
+ fault = handle_mm_fault(mm, vma, address, flags);
if (unlikely(fault & VM_FAULT_ERROR))
goto out_up;
- if (fault & VM_FAULT_MAJOR) {
- tsk->maj_flt++;
- perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0,
- regs, address);
- } else {
- tsk->min_flt++;
- perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0,
- regs, address);
+ /*
+ * Major/minor page fault accounting is only done on the
+ * initial attempt. If we go through a retry, it is extremely
+ * likely that the page will be found in page cache at that point.
+ */
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ if (fault & VM_FAULT_MAJOR) {
+ tsk->maj_flt++;
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0,
+ regs, address);
+ } else {
+ tsk->min_flt++;
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0,
+ regs, address);
+ }
+ if (fault & VM_FAULT_RETRY) {
+ /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
+ * of starvation. */
+ flags &= ~FAULT_FLAG_ALLOW_RETRY;
+ goto retry;
+ }
}
/*
* The instruction that caused the program check will