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[PATCH] md: make sure 64bit fields in version-1 metadata are 64-bit aligned

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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>
This commit is contained in:
NeilBrown 2006-04-10 22:52:48 -07:00 committed by Linus Torvalds
parent 54404e72cd
commit 6f91fe88e4
2 changed files with 7 additions and 6 deletions
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11
drivers/md/Kconfig
View File

@ -139,11 +139,12 @@ config MD_RAID5_RESHAPE
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

2
include/linux/raid/md_p.h
View File

@ -227,8 +227,8 @@ struct mdp_superblock_1 {
*/
/* 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) */