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md/raid5: use seqcount to protect access to shape in make_request. 

make_request() access various shape parameters (raid_disks, chunk_size
etc) which might be changed by raid5_start_reshape().

If the later is called at and awkward time during the form, the wrong
stripe_head might be used.

So introduce a 'seqcount' and after finding a stripe_head make sure
there is no reason to expect that we got the wrong one.

Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
NeilBrown 2013-08-27 15:52:13 +10:00
parent b721420e87
commit c46501b2de
2 changed files with 14 additions and 1 deletions
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14
drivers/md/raid5.c
View File

@ -4408,8 +4408,10 @@ static void make_request(struct mddev *mddev, struct bio * bi)
for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
DEFINE_WAIT(w);
int previous;
int seq;
retry:
seq = read_seqcount_begin(&conf->gen_lock);
previous = 0;
prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
if (unlikely(conf->reshape_progress != MaxSector)) {
@ -4442,7 +4444,7 @@ static void make_request(struct mddev *mddev, struct bio * bi)
previous,
&dd_idx, NULL);
pr_debug("raid456: make_request, sector %llu logical %llu\n",
(unsigned long long)new_sector,
(unsigned long long)new_sector,
(unsigned long long)logical_sector);
sh = get_active_stripe(conf, new_sector, previous,
@ -4471,6 +4473,13 @@ static void make_request(struct mddev *mddev, struct bio * bi)
goto retry;
}
}
if (read_seqcount_retry(&conf->gen_lock, seq)) {
/* Might have got the wrong stripe_head
* by accident
*/
release_stripe(sh);
goto retry;
}
if (rw == WRITE &&
logical_sector >= mddev->suspend_lo &&
@ -5437,6 +5446,7 @@ static struct r5conf *setup_conf(struct mddev *mddev)
if (alloc_thread_groups(conf, 0))
goto abort;
spin_lock_init(&conf->device_lock);
seqcount_init(&conf->gen_lock);
init_waitqueue_head(&conf->wait_for_stripe);
init_waitqueue_head(&conf->wait_for_overlap);
INIT_LIST_HEAD(&conf->handle_list);
@ -6249,6 +6259,7 @@ static int raid5_start_reshape(struct mddev *mddev)
atomic_set(&conf->reshape_stripes, 0);
spin_lock_irq(&conf->device_lock);
write_seqcount_begin(&conf->gen_lock);
conf->previous_raid_disks = conf->raid_disks;
conf->raid_disks += mddev->delta_disks;
conf->prev_chunk_sectors = conf->chunk_sectors;
@ -6265,6 +6276,7 @@ static int raid5_start_reshape(struct mddev *mddev)
else
conf->reshape_progress = 0;
conf->reshape_safe = conf->reshape_progress;
write_seqcount_end(&conf->gen_lock);
spin_unlock_irq(&conf->device_lock);
/* Add some new drives, as many as will fit.

1
drivers/md/raid5.h
View File

@ -400,6 +400,7 @@ struct r5conf {
int prev_chunk_sectors;
int prev_algo;
short generation; /* increments with every reshape */
seqcount_t gen_lock; /* lock against generation changes */
unsigned long reshape_checkpoint; /* Time we last updated
* metadata */
long long min_offset_diff; /* minimum difference between