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>
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index d79ecd9..4263df1 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4408,8 +4408,10 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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.