xtensa/mm/fault.c: port OOM changes to do_page_fault

d065bd810b6de ("mm: retry page fault when blocking on disk transfer") and
37b23e0525d393d ("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 xtensa.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Acked-by: Chris Zankel <chris@zankel.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/xtensa/mm/fault.c b/arch/xtensa/mm/fault.c
index b17885a0b508fe82e84b012b89539caf3862dfed..5a74c53bc69c132cfad6231d9294e49f5cedef93 100644 (file)
--- a/arch/xtensa/mm/fault.c
+++ b/arch/xtensa/mm/fault.c
@@ -44,6 +44,7 @@ void do_page_fault(struct pt_regs *regs)
 
        int is_write, is_exec;
        int fault;
+       unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
        info.si_code = SEGV_MAPERR;
 
@@ -71,6 +72,7 @@ void do_page_fault(struct pt_regs *regs)
               address, exccause, regs->pc, is_write? "w":"", is_exec? "x":"");
 #endif
 
+retry:
        down_read(&mm->mmap_sem);
        vma = find_vma(mm, address);
 
@@ -93,6 +95,7 @@ good_area:
        if (is_write) {
                if (!(vma->vm_flags & VM_WRITE))
                        goto bad_area;
+               flags |= FAULT_FLAG_WRITE;
        } else if (is_exec) {
                if (!(vma->vm_flags & VM_EXEC))
                        goto bad_area;
@@ -104,7 +107,11 @@ good_area:
         * make sure we exit gracefully rather than endlessly redo
         * the fault.
         */
-       fault = handle_mm_fault(mm, vma, address, is_write ? 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;
@@ -112,10 +119,22 @@ good_area:
                        goto do_sigbus;
                BUG();
        }
-       if (fault & VM_FAULT_MAJOR)
-               current->maj_flt++;
-       else
-               current->min_flt++;
+       if (flags & FAULT_FLAG_ALLOW_RETRY) {
+               if (fault & VM_FAULT_MAJOR)
+                       current->maj_flt++;
+               else
+                       current->min_flt++;
+               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);
        return;