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md/raid5: change reshape-progress measurement to cope with reshaping …
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…backwards.

When reducing the number of devices in a raid4/5/6, the reshape
process has to start at the end of the array and work down to the
beginning.  So we need to handle expand_progress and expand_lo
differently.

This patch renames "expand_progress" and "expand_lo" to avoid the
implication that anything is getting bigger (expand->reshape) and
every place they are used, we make sure that they are used the right
way depending on whether delta_disks is positive or negative.

Signed-off-by: NeilBrown <neilb@suse.de>
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NeilBrown committed Mar 31, 2009
1 parent cea9c22 commit fef9c61
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Showing 2 changed files with 71 additions and 38 deletions.
94 changes: 61 additions & 33 deletions drivers/md/raid5.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3593,24 +3593,28 @@ static int make_request(struct request_queue *q, struct bio * bi)
retry:
previous = 0;
prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
if (likely(conf->expand_progress == MaxSector))
if (likely(conf->reshape_progress == MaxSector))
disks = conf->raid_disks;
else {
/* spinlock is needed as expand_progress may be
/* spinlock is needed as reshape_progress may be
* 64bit on a 32bit platform, and so it might be
* possible to see a half-updated value
* Ofcourse expand_progress could change after
* Ofcourse reshape_progress could change after
* the lock is dropped, so once we get a reference
* to the stripe that we think it is, we will have
* to check again.
*/
spin_lock_irq(&conf->device_lock);
disks = conf->raid_disks;
if (logical_sector >= conf->expand_progress) {
if (mddev->delta_disks < 0
? logical_sector < conf->reshape_progress
: logical_sector >= conf->reshape_progress) {
disks = conf->previous_raid_disks;
previous = 1;
} else {
if (logical_sector >= conf->expand_lo) {
if (mddev->delta_disks < 0
? logical_sector < conf->reshape_safe
: logical_sector >= conf->reshape_safe) {
spin_unlock_irq(&conf->device_lock);
schedule();
goto retry;
Expand All @@ -3630,7 +3634,7 @@ static int make_request(struct request_queue *q, struct bio * bi)
sh = get_active_stripe(conf, new_sector, previous,
(bi->bi_rw&RWA_MASK));
if (sh) {
if (unlikely(conf->expand_progress != MaxSector)) {
if (unlikely(conf->reshape_progress != MaxSector)) {
/* expansion might have moved on while waiting for a
* stripe, so we must do the range check again.
* Expansion could still move past after this
Expand All @@ -3641,8 +3645,10 @@ static int make_request(struct request_queue *q, struct bio * bi)
*/
int must_retry = 0;
spin_lock_irq(&conf->device_lock);
if (logical_sector < conf->expand_progress &&
disks == conf->previous_raid_disks)
if ((mddev->delta_disks < 0
? logical_sector >= conf->reshape_progress
: logical_sector < conf->reshape_progress)
&& disks == conf->previous_raid_disks)
/* mismatch, need to try again */
must_retry = 1;
spin_unlock_irq(&conf->device_lock);
Expand Down Expand Up @@ -3720,42 +3726,58 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
int dd_idx;
sector_t writepos, safepos, gap;

if (sector_nr == 0 &&
conf->expand_progress != 0) {
/* restarting in the middle, skip the initial sectors */
sector_nr = conf->expand_progress;
if (sector_nr == 0) {
/* If restarting in the middle, skip the initial sectors */
if (mddev->delta_disks < 0 &&
conf->reshape_progress < raid5_size(mddev, 0, 0)) {
sector_nr = raid5_size(mddev, 0, 0)
- conf->reshape_progress;
} else if (mddev->delta_disks > 0 &&
conf->reshape_progress > 0)
sector_nr = conf->reshape_progress;
sector_div(sector_nr, new_data_disks);
*skipped = 1;
return sector_nr;
if (sector_nr) {
*skipped = 1;
return sector_nr;
}
}

/* we update the metadata when there is more than 3Meg
* in the block range (that is rather arbitrary, should
* probably be time based) or when the data about to be
* copied would over-write the source of the data at
* the front of the range.
* i.e. one new_stripe forward from expand_progress new_maps
* to after where expand_lo old_maps to
* i.e. one new_stripe along from reshape_progress new_maps
* to after where reshape_safe old_maps to
*/
writepos = conf->expand_progress +
conf->chunk_size/512*(new_data_disks);
writepos = conf->reshape_progress;
sector_div(writepos, new_data_disks);
safepos = conf->expand_lo;
safepos = conf->reshape_safe;
sector_div(safepos, data_disks);
gap = conf->expand_progress - conf->expand_lo;
if (mddev->delta_disks < 0) {
writepos -= conf->chunk_size/512;
safepos += conf->chunk_size/512;
gap = conf->reshape_safe - conf->reshape_progress;
} else {
writepos += conf->chunk_size/512;
safepos -= conf->chunk_size/512;
gap = conf->reshape_progress - conf->reshape_safe;
}

if (writepos >= safepos ||
if ((mddev->delta_disks < 0
? writepos < safepos
: writepos > safepos) ||
gap > (new_data_disks)*3000*2 /*3Meg*/) {
/* Cannot proceed until we've updated the superblock... */
wait_event(conf->wait_for_overlap,
atomic_read(&conf->reshape_stripes)==0);
mddev->reshape_position = conf->expand_progress;
mddev->reshape_position = conf->reshape_progress;
set_bit(MD_CHANGE_DEVS, &mddev->flags);
md_wakeup_thread(mddev->thread);
wait_event(mddev->sb_wait, mddev->flags == 0 ||
kthread_should_stop());
spin_lock_irq(&conf->device_lock);
conf->expand_lo = mddev->reshape_position;
conf->reshape_safe = mddev->reshape_position;
spin_unlock_irq(&conf->device_lock);
wake_up(&conf->wait_for_overlap);
}
Expand Down Expand Up @@ -3792,7 +3814,10 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
release_stripe(sh);
}
spin_lock_irq(&conf->device_lock);
conf->expand_progress = (sector_nr + i) * new_data_disks;
if (mddev->delta_disks < 0)
conf->reshape_progress -= i * new_data_disks;
else
conf->reshape_progress += i * new_data_disks;
spin_unlock_irq(&conf->device_lock);
/* Ok, those stripe are ready. We can start scheduling
* reads on the source stripes.
Expand Down Expand Up @@ -3823,14 +3848,14 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
/* Cannot proceed until we've updated the superblock... */
wait_event(conf->wait_for_overlap,
atomic_read(&conf->reshape_stripes) == 0);
mddev->reshape_position = conf->expand_progress;
mddev->reshape_position = conf->reshape_progress;
set_bit(MD_CHANGE_DEVS, &mddev->flags);
md_wakeup_thread(mddev->thread);
wait_event(mddev->sb_wait,
!test_bit(MD_CHANGE_DEVS, &mddev->flags)
|| kthread_should_stop());
spin_lock_irq(&conf->device_lock);
conf->expand_lo = mddev->reshape_position;
conf->reshape_safe = mddev->reshape_position;
spin_unlock_irq(&conf->device_lock);
wake_up(&conf->wait_for_overlap);
}
Expand Down Expand Up @@ -4283,7 +4308,7 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
conf->max_degraded = 1;
conf->algorithm = mddev->new_layout;
conf->max_nr_stripes = NR_STRIPES;
conf->expand_progress = mddev->reshape_position;
conf->reshape_progress = mddev->reshape_position;

memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +
conf->raid_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
Expand Down Expand Up @@ -4441,9 +4466,9 @@ static int run(mddev_t *mddev)

print_raid5_conf(conf);

if (conf->expand_progress != MaxSector) {
if (conf->reshape_progress != MaxSector) {
printk("...ok start reshape thread\n");
conf->expand_lo = conf->expand_progress;
conf->reshape_safe = conf->reshape_progress;
atomic_set(&conf->reshape_stripes, 0);
clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
Expand Down Expand Up @@ -4782,8 +4807,11 @@ static int raid5_start_reshape(mddev_t *mddev)
spin_lock_irq(&conf->device_lock);
conf->previous_raid_disks = conf->raid_disks;
conf->raid_disks += mddev->delta_disks;
conf->expand_progress = 0;
conf->expand_lo = 0;
if (mddev->delta_disks < 0)
conf->reshape_progress = raid5_size(mddev, 0, 0);
else
conf->reshape_progress = 0;
conf->reshape_safe = conf->reshape_progress;
spin_unlock_irq(&conf->device_lock);

/* Add some new drives, as many as will fit.
Expand Down Expand Up @@ -4825,7 +4853,7 @@ static int raid5_start_reshape(mddev_t *mddev)
mddev->recovery = 0;
spin_lock_irq(&conf->device_lock);
mddev->raid_disks = conf->raid_disks = conf->previous_raid_disks;
conf->expand_progress = MaxSector;
conf->reshape_progress = MaxSector;
spin_unlock_irq(&conf->device_lock);
return -EAGAIN;
}
Expand All @@ -4842,7 +4870,7 @@ static void end_reshape(raid5_conf_t *conf)

spin_lock_irq(&conf->device_lock);
conf->previous_raid_disks = conf->raid_disks;
conf->expand_progress = MaxSector;
conf->reshape_progress = MaxSector;
spin_unlock_irq(&conf->device_lock);

/* read-ahead size must cover two whole stripes, which is
Expand Down
15 changes: 10 additions & 5 deletions drivers/md/raid5.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -337,11 +337,16 @@ struct raid5_private_data {
int raid_disks;
int max_nr_stripes;

/* used during an expand */
sector_t expand_progress; /* MaxSector when no expand happening */
sector_t expand_lo; /* from here up to expand_progress it out-of-bounds
* as we haven't flushed the metadata yet
*/
/* reshape_progress is the leading edge of a 'reshape'
* It has value MaxSector when no reshape is happening
* If delta_disks < 0, it is the last sector we started work on,
* else is it the next sector to work on.
*/
sector_t reshape_progress;
/* reshape_safe is the trailing edge of a reshape. We know that
* before (or after) this address, all reshape has completed.
*/
sector_t reshape_safe;
int previous_raid_disks;

struct list_head handle_list; /* stripes needing handling */
Expand Down

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