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md: add possibility to change data-offset for devices.

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When reshaping we can avoid costly intermediate backup by
changing the 'start' address of the array on the device
(if there is enough room).

So as a first step, allow such a change to be requested
through sysfs, and recorded in v1.x metadata.

(As we didn't previous check that all 'pad' fields were zero,
 we need a new FEATURE flag for this.
 A (belatedly) check that all remaining 'pad' fields are
 zero to avoid a repeat of this)

The new data offset must be requested separately for each device.
This allows each to have a different change in the data offset.
This is not likely to be used often but as data_offset can be
set per-device, new_data_offset should be too.

This patch also removes the 'acknowledged' arg to rdev_set_badblocks as
it is never used and never will be.  At the same time we add a new
arg ('in_new') which is currently always zero but will be used more
soon.

When a reshape finishes we will need to update the data_offset
and rdev->sectors.  So provide an exported function to do that.

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2012-05-21 09:27:00 +10:00
parent 2c810cddc4
commit c6563a8c38
6 changed files with 222 additions and 34 deletions
Download patch file Download diff file Expand all files Collapse all files

10
include/linux/raid/md_p.h
View file

@ -233,7 +233,10 @@ struct mdp_superblock_1 {
__le32 delta_disks; /* change in number of raid_disks */
__le32 new_layout; /* new layout */
__le32 new_chunk; /* new chunk size (512byte sectors) */
__u8 pad1[128-124]; /* set to 0 when written */
__le32 new_offset; /* signed number to add to data_offset in new
* layout. 0 == no-change. This can be
* different on each device in the array.
*/
/* constant this-device information - 64 bytes */
__le64 data_offset; /* sector start of data, often 0 */
@ -285,11 +288,14 @@ struct mdp_superblock_1 {
* of devices, but is going
* backwards anyway.
*/
#define MD_FEATURE_NEW_OFFSET 64 /* new_offset must be honoured */
#define MD_FEATURE_ALL (MD_FEATURE_BITMAP_OFFSET \
|MD_FEATURE_RECOVERY_OFFSET \
|MD_FEATURE_RESHAPE_ACTIVE \
|MD_FEATURE_BAD_BLOCKS \
|MD_FEATURE_REPLACEMENT \
|MD_FEATURE_RESHAPE_BACKWARDS)
|MD_FEATURE_RESHAPE_BACKWARDS \
|MD_FEATURE_NEW_OFFSET \
)
#endif