1 files changed, 39 insertions, 19 deletions

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index aa33949fef60..4aabeaec25df 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -231,7 +231,7 @@ static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
 
 static int __kprobes
 __do_page_fault(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;
@@ -253,18 +253,7 @@ good_area:
                 goto out;
         }
 
-        /*
-         * 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 & FSR_WRITE) ? FAULT_FLAG_WRITE : 0);
-        if (unlikely(fault & VM_FAULT_ERROR))
-                return fault;
-        if (fault & VM_FAULT_MAJOR)
-                tsk->maj_flt++;
-        else
-                tsk->min_flt++;
-        return fault;
+        return handle_mm_fault(mm, vma, addr & PAGE_MASK, flags);
 
 check_stack:
         if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
@@ -279,6 +268,9 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
         struct task_struct *tsk;
         struct mm_struct *mm;
         int fault, sig, code;
+        int write = fsr & FSR_WRITE;
+        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+                                (write ? FAULT_FLAG_WRITE : 0);
 
         if (notify_page_fault(regs, fsr))
                 return 0;
@@ -305,6 +297,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
         if (!down_read_trylock(&mm->mmap_sem)) {
                 if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
                         goto no_context;
+retry:
                 down_read(&mm->mmap_sem);
         } else {
                 /*
@@ -320,14 +313,41 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 #endif
         }
 
-        fault = __do_page_fault(mm, addr, fsr, tsk);
-        up_read(&mm->mmap_sem);
+        fault = __do_page_fault(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;
+
+        /*
+         * 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.
+         */
 
         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
-        if (fault & VM_FAULT_MAJOR)
-                perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, addr);
-        else if (fault & VM_FAULT_MINOR)
-                perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, addr);
+        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, addr);
+                } else {
+                        tsk->min_flt++;
+                        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
+                                        regs, addr);
+                }
+                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);
 
         /*
          * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR