btrfs: move eb offset helpers into extent_io.h

These are very specific to how the extent buffer is defined, so this
differs between btrfs-progs and the kernel.  Make things easier by
moving these helpers into extent_io.h so we don't have to worry about
this when syncing ctree.h.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 9b486419854e..a2c82448b2e0 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -96,6 +96,39 @@ struct extent_buffer {
 };
 
 /*
+ * Get the correct offset inside the page of extent buffer.
+ *
+ * @eb:		target extent buffer
+ * @start:	offset inside the extent buffer
+ *
+ * Will handle both sectorsize == PAGE_SIZE and sectorsize < PAGE_SIZE cases.
+ */
+static inline size_t get_eb_offset_in_page(const struct extent_buffer *eb,
+					   unsigned long offset)
+{
+	/*
+	 * For sectorsize == PAGE_SIZE case, eb->start will always be aligned
+	 * to PAGE_SIZE, thus adding it won't cause any difference.
+	 *
+	 * For sectorsize < PAGE_SIZE, we must only read the data that belongs
+	 * to the eb, thus we have to take the eb->start into consideration.
+	 */
+	return offset_in_page(offset + eb->start);
+}
+
+static inline unsigned long get_eb_page_index(unsigned long offset)
+{
+	/*
+	 * For sectorsize == PAGE_SIZE case, plain >> PAGE_SHIFT is enough.
+	 *
+	 * For sectorsize < PAGE_SIZE case, we only support 64K PAGE_SIZE,
+	 * and have ensured that all tree blocks are contained in one page,
+	 * thus we always get index == 0.
+	 */
+	return offset >> PAGE_SHIFT;
+}
+
+/*
  * Structure to record how many bytes and which ranges are set/cleared
  */
 struct extent_changeset {