avr32/mm/fault.c: port OOM changes to do_page_fault
Kautuk Consul [Mon, 30 Jul 2012 21:39:25 +0000 (14:39 -0700)]
Commits d065bd810b6d ("mm: retry page fault when blocking on disk
transfer") and 37b23e0525d3 ("x86,mm: make pagefault killable")
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 AVR32.

[akpm@linux-foundation.org: fix comment layout]
Signed-off-by: Mohd. Faris <mohdfarisq2010@gmail.com>
Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Acked-by: Havard Skinnemoen <hskinnemoen@gmail.com>
Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/avr32/mm/fault.c

index f7040a1..b92e609 100644 (file)
@@ -61,10 +61,10 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
        const struct exception_table_entry *fixup;
        unsigned long address;
        unsigned long page;
-       int writeaccess;
        long signr;
        int code;
        int fault;
+       unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
        if (notify_page_fault(regs, ecr))
                return;
@@ -86,6 +86,7 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
 
        local_irq_enable();
 
+retry:
        down_read(&mm->mmap_sem);
 
        vma = find_vma(mm, address);
@@ -104,7 +105,6 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
         */
 good_area:
        code = SEGV_ACCERR;
-       writeaccess = 0;
 
        switch (ecr) {
        case ECR_PROTECTION_X:
@@ -121,7 +121,7 @@ good_area:
        case ECR_TLB_MISS_W:
                if (!(vma->vm_flags & VM_WRITE))
                        goto bad_area;
-               writeaccess = 1;
+               flags |= FAULT_FLAG_WRITE;
                break;
        default:
                panic("Unhandled case %lu in do_page_fault!", ecr);
@@ -132,7 +132,11 @@ good_area:
         * sure we exit gracefully rather than endlessly redo the
         * fault.
         */
-       fault = handle_mm_fault(mm, vma, address, writeaccess ? 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;
@@ -140,10 +144,23 @@ good_area:
                        goto do_sigbus;
                BUG();
        }
-       if (fault & VM_FAULT_MAJOR)
-               tsk->maj_flt++;
-       else
-               tsk->min_flt++;
+
+       if (flags & FAULT_FLAG_ALLOW_RETRY) {
+               if (fault & VM_FAULT_MAJOR)
+                       tsk->maj_flt++;
+               else
+                       tsk->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;