[PATCH] md: make sure 64bit fields in version-1 metadata are 64-bit aligned
reshape_position is a 64bit field that was not 64bit aligned. So swap with
new_level.
NOTE: this is a user-visible change. However:
- The bad code has not appeared in a released kernel
- This code is still marked 'experimental'
- This only affects version-1 superblock, which are not in wide use
- These field are only used (rather than simply reported) by user-space
tools in extemely rare circumstances : after a reshape crashes in the
first second of the reshape process.
So I believe that, at this stage, the change is safe. Especially if people
heed the 'help' message on use mdadm-2.4.1.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index fd2aae1..ac25a48 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -139,11 +139,12 @@
is online. However it is still EXPERIMENTAL code. It should
work, but please be sure that you have backups.
- You will need a version of mdadm newer than 2.3.1. During the
- early stage of reshape there is a critical section where live data
- is being over-written. A crash during this time needs extra care
- for recovery. The newer mdadm takes a copy of the data in the
- critical section and will restore it, if necessary, after a crash.
+ You will need mdadm verion 2.4.1 or later to use this
+ feature safely. During the early stage of reshape there is
+ a critical section where live data is being over-written. A
+ crash during this time needs extra care for recovery. The
+ newer mdadm takes a copy of the data in the critical section
+ and will restore it, if necessary, after a crash.
The mdadm usage is e.g.
mdadm --grow /dev/md1 --raid-disks=6
diff --git a/include/linux/raid/md_p.h b/include/linux/raid/md_p.h
index 774e1ac..f1fbae7 100644
--- a/include/linux/raid/md_p.h
+++ b/include/linux/raid/md_p.h
@@ -227,8 +227,8 @@
*/
/* These are only valid with feature bit '4' */
- __u64 reshape_position; /* next address in array-space for reshape */
__u32 new_level; /* new level we are reshaping to */
+ __u64 reshape_position; /* next address in array-space for reshape */
__u32 delta_disks; /* change in number of raid_disks */
__u32 new_layout; /* new layout */
__u32 new_chunk; /* new chunk size (bytes) */