From: Goldwyn Rodrigues <rgold...@suse.com>
Create a page size extent and copy the contents of the original
extent into the new one, and present to user space as the page
to write.
Signed-off-by: Goldwyn Rodrigues <rgold...@suse.com>
---
fs/btrfs/dax.c | 39 +++++++++++++++++++++++++++++++++++++++
1 file changed, 39 insertions(+)
diff --git a/fs/btrfs/dax.c b/fs/btrfs/dax.c
index 6d68d39cc5da..4634917877f3 100644
--- a/fs/btrfs/dax.c
+++ b/fs/btrfs/dax.c
@@ -231,6 +231,45 @@ vm_fault_t btrfs_dax_fault(struct vm_fault *vmf)
sector >>= 9;
ret = copy_user_dax(em->bdev, dax_dev, sector, PAGE_SIZE,
vmf->cow_page, vaddr);
goto out;
+ } else if (vmf->flags & FAULT_FLAG_WRITE) {
+ pfn_t pfn;
+ struct extent_map *orig = em;
+ void *daddr;
+ sector_t dstart;
+ size_t maplen;
+ struct extent_changeset *data_reserved = NULL;
+ struct extent_state *cached_state = NULL;
+
+ ret = btrfs_delalloc_reserve_space(inode, &data_reserved, pos,
PAGE_SIZE);
+ if (ret < 0)
+ return ret;
+ refcount_inc(&orig->refs);
+ lock_extent_bits(&BTRFS_I(inode)->io_tree, pos, pos +
PAGE_SIZE, &cached_state);
+ /* Create an extent of page size */
+ ret = btrfs_get_extent_map_write(&em, NULL, inode, pos,
+ PAGE_SIZE);
+ if (ret < 0) {
+ free_extent_map(orig);
+ btrfs_delalloc_release_space(inode, data_reserved, pos,
+ PAGE_SIZE, true);
+ goto out;
+ }
+
+ dax_dev = fs_dax_get_by_bdev(em->bdev);
+ /* Calculate start address of destination extent */
+ dstart = (get_start_sect(em->bdev) << 9) + em->block_start;
+ maplen = dax_direct_access(dax_dev, PHYS_PFN(dstart),
+ 1, &daddr, &pfn);
+
+ /* Copy the original contents into new destination */
+ copy_extent_page(orig, daddr, pos);
+ btrfs_update_ordered_extent(inode, pos, PAGE_SIZE, true);
+ dax_insert_entry(&xas, mapping, vmf, entry, pfn, 0, false);
+ ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
+ free_extent_map(orig);
+ unlock_extent_cached(&BTRFS_I(inode)->io_tree, pos, pos +
PAGE_SIZE, &cached_state);
+ extent_changeset_free(data_reserved);
+ btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE,
false);
} else {
sector_t sector;
if (em->block_start == EXTENT_MAP_HOLE) {
--
2.16.4
