From: Doug Ledford <dledford@redhat.com>
Date: Tue, 4 Dec 2007 12:40:07 -0500
Subject: [md] fix bitmap support
Message-id: 1196790007.11746.46.camel@firewall.xsintricity.com
O-Subject: [Patch RHEL5] Fix md bitmap support (bz219338 and bz210178)
Bugzilla: 210178

There are two patches in one here.  They both are needed to get our md
bitmap support operational on ppc64 kernels.  The first problem is that
our 64bit kernels are missing a couple 32bit compat ioctls related to
bitmaps (bz219338).  No big deal everywhere except ppc where by default
we have a 64bit kernel and 32bit userland.  I tested the compat ioctl
stuff by running the i386 mdadm on an x86_64 kernel with the patch
applied (plus it's all upstream too, as well as having been tested by
both IBM and Steeleye).  The second patch is related to big endian
machines.  Specifically, find_first_bit on big endian machines doesn't
find the least significant bit first (bz210178).  However, find first
zero of the ~ does find the right item.  The second patch does that.  I
don't have the means to test this, but it's upstream, it's a common
practice in the kernel in general to use ffz(~variable); to find the
least significant bit when the code will run on big endian machines, and
the people at Steeleye have tested this.

First patch:

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index ecc5676..3d0e764 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1430,8 +1430,7 @@ int bitmap_create(mddev_t *mddev)
 	if (err)
 		goto error;
 
-	bitmap->chunkshift = find_first_bit(&bitmap->chunksize,
-					sizeof(bitmap->chunksize));
+	bitmap->chunkshift = ffz(~bitmap->chunksize);
 
 	/* now that chunksize and chunkshift are set, we can use these macros */
  	chunks = (blocks + CHUNK_BLOCK_RATIO(bitmap) - 1) /
diff --git a/include/linux/compat_ioctl.h b/include/linux/compat_ioctl.h
index bea0255..a044316 100644
--- a/include/linux/compat_ioctl.h
+++ b/include/linux/compat_ioctl.h
@@ -124,6 +124,8 @@ ULONG_IOCTL(START_ARRAY)
 COMPATIBLE_IOCTL(STOP_ARRAY)
 COMPATIBLE_IOCTL(STOP_ARRAY_RO)
 COMPATIBLE_IOCTL(RESTART_ARRAY_RW)
+ULONG_IOCTL(SET_BITMAP_FILE)
+COMPATIBLE_IOCTL(GET_BITMAP_FILE)
 /* DM */
 COMPATIBLE_IOCTL(DM_VERSION_32)
 COMPATIBLE_IOCTL(DM_REMOVE_ALL_32)