nfsd4: make op_cacheresult another flag

[pandora-kernel.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index 3c9f3aa..a56e3ba 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1805,7 +1805,63 @@ next_page:
 }
 EXPORT_SYMBOL(__get_user_pages);
 
-/**
+/*
+ * fixup_user_fault() - manually resolve a user page fault
+ * @tsk:       the task_struct to use for page fault accounting, or
+ *             NULL if faults are not to be recorded.
+ * @mm:                mm_struct of target mm
+ * @address:   user address
+ * @fault_flags:flags to pass down to handle_mm_fault()
+ *
+ * This is meant to be called in the specific scenario where for locking reasons
+ * we try to access user memory in atomic context (within a pagefault_disable()
+ * section), this returns -EFAULT, and we want to resolve the user fault before
+ * trying again.
+ *
+ * Typically this is meant to be used by the futex code.
+ *
+ * The main difference with get_user_pages() is that this function will
+ * unconditionally call handle_mm_fault() which will in turn perform all the
+ * necessary SW fixup of the dirty and young bits in the PTE, while
+ * handle_mm_fault() only guarantees to update these in the struct page.
+ *
+ * This is important for some architectures where those bits also gate the
+ * access permission to the page because they are maintained in software.  On
+ * such architectures, gup() will not be enough to make a subsequent access
+ * succeed.
+ *
+ * This should be called with the mm_sem held for read.
+ */
+int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
+                    unsigned long address, unsigned int fault_flags)
+{
+       struct vm_area_struct *vma;
+       int ret;
+
+       vma = find_extend_vma(mm, address);
+       if (!vma || address < vma->vm_start)
+               return -EFAULT;
+
+       ret = handle_mm_fault(mm, vma, address, fault_flags);
+       if (ret & VM_FAULT_ERROR) {
+               if (ret & VM_FAULT_OOM)
+                       return -ENOMEM;
+               if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
+                       return -EHWPOISON;
+               if (ret & VM_FAULT_SIGBUS)
+                       return -EFAULT;
+               BUG();
+       }
+       if (tsk) {
+               if (ret & VM_FAULT_MAJOR)
+                       tsk->maj_flt++;
+               else
+                       tsk->min_flt++;
+       }
+       return 0;
+}
+
+/*
  * get_user_pages() - pin user pages in memory
  * @tsk:       the task_struct to use for page fault accounting, or
  *             NULL if faults are not to be recorded.