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

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>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/md/md.h b/drivers/md/md.h
index d51c0ca37777..98913e8dac1a 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -55,6 +55,7 @@ struct md_rdev {
         int             sb_loaded;
         __u64           sb_events;
         sector_t        data_offset;    /* start of data in array */
+        sector_t        new_data_offset;/* only relevant while reshaping */
         sector_t        sb_start;       /* offset of the super block (in 512byte sectors) */
         int             sb_size;        /* bytes in the superblock */
         int             preferred_minor;        /* autorun support */
@@ -193,8 +194,9 @@ static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
         return 0;
 }
 extern int rdev_set_badblocks(struct md_rdev *rdev, sector_t s, int sectors,
-                              int acknowledged);
-extern int rdev_clear_badblocks(struct md_rdev *rdev, sector_t s, int sectors);
+                              int is_new);
+extern int rdev_clear_badblocks(struct md_rdev *rdev, sector_t s, int sectors,
+                                int is_new);
 extern void md_ack_all_badblocks(struct badblocks *bb);
 
 struct mddev {
@@ -592,6 +594,7 @@ extern void md_write_start(struct mddev *mddev, struct bio *bi);
 extern void md_write_end(struct mddev *mddev);
 extern void md_done_sync(struct mddev *mddev, int blocks, int ok);
 extern void md_error(struct mddev *mddev, struct md_rdev *rdev);
+extern void md_finish_reshape(struct mddev *mddev);
 
 extern int mddev_congested(struct mddev *mddev, int bits);
 extern void md_flush_request(struct mddev *mddev, struct bio *bio);