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md/raid5: allow for change in data_offset while managing a reshape. 

The important issue here is incorporating the different in data_offset
into calculations concerning when we might need to over-write data
that is still thought to be valid.

To this end we find the minimum offset difference across all devices
and add that where appropriate.

Signed-off-by: NeilBrown <neilb@suse.de>
hifive-unleashed-5.1
NeilBrown 2012-05-21 09:27:01 +10:00
parent 05616be5e1
commit b5254dd5fd
2 changed files with 82 additions and 33 deletions
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109
drivers/md/raid5.c
View File

@ -4165,13 +4165,11 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
else
reshape_sectors = mddev->chunk_sectors;
/* 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 along from reshape_progress new_maps
* to after where reshape_safe old_maps to
/* We update the metadata at least every 10 seconds, 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
* along from reshape_progress new_maps to after where
* reshape_safe old_maps to
*/
writepos = conf->reshape_progress;
sector_div(writepos, new_data_disks);
@ -4189,11 +4187,29 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
safepos -= min_t(sector_t, reshape_sectors, safepos);
}
/* Having calculated the 'writepos' possibly use it
* to set 'stripe_addr' which is where we will write to.
*/
if (mddev->reshape_backwards) {
BUG_ON(conf->reshape_progress == 0);
stripe_addr = writepos;
BUG_ON((mddev->dev_sectors &
~((sector_t)reshape_sectors - 1))
- reshape_sectors - stripe_addr
!= sector_nr);
} else {
BUG_ON(writepos != sector_nr + reshape_sectors);
stripe_addr = sector_nr;
}
/* 'writepos' is the most advanced device address we might write.
* 'readpos' is the least advanced device address we might read.
* 'safepos' is the least address recorded in the metadata as having
* been reshaped.
* If 'readpos' is behind 'writepos', then there is no way that we can
* If there is a min_offset_diff, these are adjusted either by
* increasing the safepos/readpos if diff is negative, or
* increasing writepos if diff is positive.
* If 'readpos' is then behind 'writepos', there is no way that we can
* ensure safety in the face of a crash - that must be done by userspace
* making a backup of the data. So in that case there is no particular
* rush to update metadata.
@ -4206,6 +4222,12 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
* Maybe that number should be configurable, but I'm not sure it is
* worth it.... maybe it could be a multiple of safemode_delay???
*/
if (conf->min_offset_diff < 0) {
safepos += -conf->min_offset_diff;
readpos += -conf->min_offset_diff;
} else
writepos += conf->min_offset_diff;
if ((mddev->reshape_backwards
? (safepos > writepos && readpos < writepos)
: (safepos < writepos && readpos > writepos)) ||
@ -4227,17 +4249,6 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr, int *sk
sysfs_notify(&mddev->kobj, NULL, "sync_completed");
}
if (mddev->reshape_backwards) {
BUG_ON(conf->reshape_progress == 0);
stripe_addr = writepos;
BUG_ON((mddev->dev_sectors &
~((sector_t)reshape_sectors - 1))
- reshape_sectors - stripe_addr
!= sector_nr);
} else {
BUG_ON(writepos != sector_nr + reshape_sectors);
stripe_addr = sector_nr;
}
INIT_LIST_HEAD(&stripes);
for (i = 0; i < reshape_sectors; i += STRIPE_SECTORS) {
int j;
@ -4984,16 +4995,42 @@ static int run(struct mddev *mddev)
struct md_rdev *rdev;
sector_t reshape_offset = 0;
int i;
long long min_offset_diff = 0;
int first = 1;
if (mddev->recovery_cp != MaxSector)
printk(KERN_NOTICE "md/raid:%s: not clean"
" -- starting background reconstruction\n",
mdname(mddev));
rdev_for_each(rdev, mddev) {
long long diff;
if (rdev->raid_disk < 0)
continue;
diff = (rdev->new_data_offset - rdev->data_offset);
if (first) {
min_offset_diff = diff;
first = 0;
} else if (mddev->reshape_backwards &&
diff < min_offset_diff)
min_offset_diff = diff;
else if (!mddev->reshape_backwards &&
diff > min_offset_diff)
min_offset_diff = diff;
}
if (mddev->reshape_position != MaxSector) {
/* Check that we can continue the reshape.
* Currently only disks can change, it must
* increase, and we must be past the point where
* a stripe over-writes itself
* Difficulties arise if the stripe we would write to
* next is at or after the stripe we would read from next.
* For a reshape that changes the number of devices, this
* is only possible for a very short time, and mdadm makes
* sure that time appears to have past before assembling
* the array. So we fail if that time hasn't passed.
* For a reshape that keeps the number of devices the same
* mdadm must be monitoring the reshape can keeping the
* critical areas read-only and backed up. It will start
* the array in read-only mode, so we check for that.
*/
sector_t here_new, here_old;
int old_disks;
@ -5025,26 +5062,34 @@ static int run(struct mddev *mddev)
/* here_old is the first stripe that we might need to read
* from */
if (mddev->delta_disks == 0) {
if ((here_new * mddev->new_chunk_sectors !=
here_old * mddev->chunk_sectors)) {
printk(KERN_ERR "md/raid:%s: reshape position is"
" confused - aborting\n", mdname(mddev));
return -EINVAL;
}
/* We cannot be sure it is safe to start an in-place
* reshape. It is only safe if user-space if monitoring
* reshape. It is only safe if user-space is monitoring
* and taking constant backups.
* mdadm always starts a situation like this in
* readonly mode so it can take control before
* allowing any writes. So just check for that.
*/
if ((here_new * mddev->new_chunk_sectors !=
here_old * mddev->chunk_sectors) ||
mddev->ro == 0) {
printk(KERN_ERR "md/raid:%s: in-place reshape must be started"
" in read-only mode - aborting\n",
if (abs(min_offset_diff) >= mddev->chunk_sectors &&
abs(min_offset_diff) >= mddev->new_chunk_sectors)
/* not really in-place - so OK */;
else if (mddev->ro == 0) {
printk(KERN_ERR "md/raid:%s: in-place reshape "
"must be started in read-only mode "
"- aborting\n",
mdname(mddev));
return -EINVAL;
}
} else if (mddev->reshape_backwards
? (here_new * mddev->new_chunk_sectors <=
? (here_new * mddev->new_chunk_sectors + min_offset_diff <=
here_old * mddev->chunk_sectors)
: (here_new * mddev->new_chunk_sectors >=
here_old * mddev->chunk_sectors)) {
here_old * mddev->chunk_sectors + (-min_offset_diff))) {
/* Reading from the same stripe as writing to - bad */
printk(KERN_ERR "md/raid:%s: reshape_position too early for "
"auto-recovery - aborting.\n",
@ -5069,6 +5114,7 @@ static int run(struct mddev *mddev)
if (IS_ERR(conf))
return PTR_ERR(conf);
conf->min_offset_diff = min_offset_diff;
mddev->thread = conf->thread;
conf->thread = NULL;
mddev->private = conf;
@ -5541,9 +5587,6 @@ static int raid5_start_reshape(struct mddev *mddev)
return -ENOSPC;
rdev_for_each(rdev, mddev) {
/* Don't support changing data_offset yet */
if (rdev->new_data_offset != rdev->data_offset)
return -EINVAL;
if (!test_bit(In_sync, &rdev->flags)
&& !test_bit(Faulty, &rdev->flags))
spares++;

6
drivers/md/raid5.h
View File

@ -385,6 +385,12 @@ struct r5conf {
short generation; /* increments with every reshape */
unsigned long reshape_checkpoint; /* Time we last updated
* metadata */
long long min_offset_diff; /* minimum difference between
* data_offset and
* new_data_offset across all
* devices. May be negative,
* but is closest to zero.
*/
struct list_head handle_list; /* stripes needing handling */
struct list_head hold_list; /* preread ready stripes */