unicore32/mm/fault.c: Port OOM changes to do_pf

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 unicore32.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Acked-by: Guan Xuetao <gxt@mprc.pku.edu.cn>

1 files changed, 27 insertions, 10 deletions

diff --git a/arch/unicore32/mm/fault.c b/arch/unicore32/mm/fault.c
index 2eeb9c04cab0..f9b5c10bccee 100644
--- a/arch/unicore32/mm/fault.c
+++ b/arch/unicore32/mm/fault.c
@@ -168,7 +168,7 @@ static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
 }
 
 static int __do_pf(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
-                struct task_struct *tsk)
+                unsigned int flags, struct task_struct *tsk)
 {
         struct vm_area_struct *vma;
         int fault;
@@ -194,14 +194,7 @@ good_area:
          * 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, addr & PAGE_MASK,
-                            (!(fsr ^ 0x12)) ? FAULT_FLAG_WRITE : 0);
-        if (unlikely(fault & VM_FAULT_ERROR))
-                return fault;
-        if (fault & VM_FAULT_MAJOR)
-                tsk->maj_flt++;
-        else
-                tsk->min_flt++;
+        fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, flags);
         return fault;
 
 check_stack:
@@ -216,6 +209,8 @@ static int do_pf(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
         struct task_struct *tsk;
         struct mm_struct *mm;
         int fault, sig, code;
+        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+                                 ((!(fsr ^ 0x12)) ? FAULT_FLAG_WRITE : 0);
 
         tsk = current;
         mm = tsk->mm;
@@ -236,6 +231,7 @@ static int do_pf(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
                 if (!user_mode(regs)
                     && !search_exception_tables(regs->UCreg_pc))
                         goto no_context;
+retry:
                 down_read(&mm->mmap_sem);
         } else {
                 /*
@@ -251,7 +247,28 @@ static int do_pf(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 #endif
         }
 
-        fault = __do_pf(mm, addr, fsr, tsk);
+        fault = __do_pf(mm, addr, fsr, flags, tsk);
+
+        /* If we need to retry but a fatal signal is pending, handle the
+         * signal first. We do not need to release the mmap_sem because
+         * it would already be released in __lock_page_or_retry in
+         * mm/filemap.c. */
+        if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+                return 0;
+
+        if (!(fault & VM_FAULT_ERROR) && (flags & FAULT_FLAG_ALLOW_RETRY)) {
+                if (fault & VM_FAULT_MAJOR)
+                        tsk->maj_flt++;
+                else
+                        tsk->min_flt++;
+                if (fault & VM_FAULT_RETRY) {
+                        /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
+                        * of starvation. */
+                        flags &= ~FAULT_FLAG_ALLOW_RETRY;
+                        goto retry;
+                }
+        }
+
         up_read(&mm->mmap_sem);
 
         /*