From: NeilBrown Date: Tue, 11 Apr 2006 05:52:48 +0000 (-0700) Subject: [PATCH] md: make sure 64bit fields in version-1 metadata are 64-bit aligned X-Git-Tag: v2.6.17-rc2~273 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6f91fe88e4e28b40b4f08d99e0ea6d17b70e9567;p=linux-2.6 [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig index fd2aae150c..ac25a48362 100644 --- a/drivers/md/Kconfig +++ b/drivers/md/Kconfig @@ -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 diff --git a/include/linux/raid/md_p.h b/include/linux/raid/md_p.h index 774e1acfb8..f1fbae7e39 100644 --- a/include/linux/raid/md_p.h +++ b/include/linux/raid/md_p.h @@ -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) */