[PATCH] Use do_div() instead of native 64-bit division in btrfs_ordered_sum_size()

[David Woodhouse <dwmw2@infradead.org>]

Prevents the compiler emitting calls to __udivdi3() from libgcc on some
platforms:
WARNING: "__udivdi3" [/shiny/git/btrfs-kernel-unstable/btrfs.ko] undefi=
ned!

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
---
Untested but ObviouslyCorrect=E2=84=A2. Now that I can load the module,=
 I hit a
BUG() immediately -- but I don't think it's caused by this patch. qv.

diff --git a/ordered-data.h b/ordered-data.h
index 1794efd..1abe5f5 100644
--- a/ordered-data.h
+++ b/ordered-data.h
@@ -97,9 +97,12 @@ struct btrfs_ordered_extent {
  */
 static inline int btrfs_ordered_sum_size(struct btrfs_root *root, u64 =
bytes)
 {
-	unsigned long num_sectors =3D (bytes + root->sectorsize - 1) /
-		root->sectorsize;
-	num_sectors++;
+	unsigned long num_sectors;
+
+	bytes +=3D root->sectorsize - 1;
+	do_div(bytes, root->sectorsize);
+	num_sectors =3D bytes + 1;
+
 	return sizeof(struct btrfs_ordered_sum) +
 		num_sectors * sizeof(struct btrfs_sector_sum);
 }

--=20
David Woodhouse                            Open Source Technology Centr=
e
David.Woodhouse@intel.com                              Intel Corporatio=
n


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