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md: allow resync_start to be set while an array is active.

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The sysfs attribute 'resync_start' (known internally as recovery_cp),
records where a resync is up to.  A value of 0 means the array is
not known to be in-sync at all.  A value of MaxSector means the array
is believed to be fully in-sync.

When the size of member devices of an array (RAID1,RAID4/5/6) is
increased, the array can be increased to match.  This process sets
resync_start to the old end-of-device offset so that the new part of
the array gets resynced.

However with RAID1 (and RAID6) a resync is not technically necessary
and may be undesirable.  So it would be good if the implied resync
after the array is resized could be avoided.

So: change 'resync_start' so the value can be changed while the array
is active, and as a precaution only allow it to be changed while
resync/recovery is 'frozen'.  Changing it once resync has started is
not going to be useful anyway.

This allows the array to be resized without a resync by:
  write 'frozen' to 'sync_action'
  write new size to 'component_size' (this will set resync_start)
  write 'none' to 'resync_start'
  write 'idle' to 'sync_action'.

Also slightly improve some tests on recovery_cp when resizing
raid1/raid5.  Now that an arbitrary value could be set we should be
more careful in our tests.

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2011-05-11 15:52:21 +10:00
parent ab9d47e990
commit b098636cf0
3 changed files with 4 additions and 3 deletions
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2
drivers/md/md.c
View File

@ -3324,7 +3324,7 @@ resync_start_store(mddev_t *mddev, const char *buf, size_t len)
char *e;
unsigned long long n = simple_strtoull(buf, &e, 10);
if (mddev->pers)
if (mddev->pers && !test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
return -EBUSY;
if (cmd_match(buf, "none"))
n = MaxSector;

2
drivers/md/raid1.c
View File

@ -2061,7 +2061,7 @@ static int raid1_resize(mddev_t *mddev, sector_t sectors)
set_capacity(mddev->gendisk, mddev->array_sectors);
revalidate_disk(mddev->gendisk);
if (sectors > mddev->dev_sectors &&
mddev->recovery_cp == MaxSector) {
mddev->recovery_cp > mddev->dev_sectors) {
mddev->recovery_cp = mddev->dev_sectors;
set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
}

3
drivers/md/raid5.c
View File

@ -5389,7 +5389,8 @@ static int raid5_resize(mddev_t *mddev, sector_t sectors)
return -EINVAL;
set_capacity(mddev->gendisk, mddev->array_sectors);
revalidate_disk(mddev->gendisk);
if (sectors > mddev->dev_sectors && mddev->recovery_cp == MaxSector) {
if (sectors > mddev->dev_sectors &&
mddev->recovery_cp > mddev->dev_sectors) {
mddev->recovery_cp = mddev->dev_sectors;
set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
}