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>

diff --git a/arch/unicore32/mm/fault.c b/arch/unicore32/mm/fault.c
index 2eeb9c04cab057b5a2c6f542e251d6762cd6621b..f9b5c10bccee96e8838484aaf6effc39b3c89bd1 100644 (file)
--- 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);
 
        /*