Merge tag 'libnvdimm-for-4.3' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm...

[cascardo/linux.git] / fs / dax.c

diff --git a/fs/dax.c b/fs/dax.c
index 7c634ac..57bb70b 100644 (file)
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -332,6 +332,12 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
  * @vma: The virtual memory area where the fault occurred
  * @vmf: The description of the fault
  * @get_block: The filesystem method used to translate file offsets to blocks
+ * @complete_unwritten: The filesystem method used to convert unwritten blocks
+ *     to written so the data written to them is exposed. This is required for
+ *     required by write faults for filesystems that will return unwritten
+ *     extent mappings from @get_block, but it is optional for reads as
+ *     dax_insert_mapping() will always zero unwritten blocks. If the fs does
+ *     not support unwritten extents, the it should pass NULL.
  *
  * When a page fault occurs, filesystems may call this helper in their
  * fault handler for DAX files. __dax_fault() assumes the caller has done all
@@ -450,8 +456,12 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
         * as for normal BH based IO completions.
         */
        error = dax_insert_mapping(inode, &bh, vma, vmf);
-       if (buffer_unwritten(&bh))
-               complete_unwritten(&bh, !error);
+       if (buffer_unwritten(&bh)) {
+               if (complete_unwritten)
+                       complete_unwritten(&bh, !error);
+               else
+                       WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE));
+       }
 
  out:
        if (error == -ENOMEM)