dm integrity: implement synchronous mode for reboot handling

Unfortunatelly, there may be bios coming even after the reboot notifier
was called. We don't want these bios to make the bitmap dirty again.

To address this, implement a synchronous mode - when a bio is about to
be terminated, we clean the bitmap and terminate the bio after the clean
operation succeeds. This obviously slows down bio processing, but it
makes sure that when all bios are finished, the bitmap will be clean.

Signed-off-by: Mikulas Patocka <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

drivers/md/dm-integrity.c

···
 	struct page_list *may_write_bitmap;
 	struct bitmap_block_status *bbs;
 	unsigned bitmap_flush_interval;
+	int synchronous_mode;
+	struct bio_list synchronous_bios;
 	struct delayed_work bitmap_flush_work;
 
 	struct crypto_skcipher *journal_crypt;
···
 	int r = dm_integrity_failed(ic);
 	if (unlikely(r) && !bio->bi_status)
 		bio->bi_status = errno_to_blk_status(r);
+	if (unlikely(ic->synchronous_mode) && bio_op(bio) == REQ_OP_WRITE) {
+		unsigned long flags;
+		spin_lock_irqsave(&ic->endio_wait.lock, flags);
+		bio_list_add(&ic->synchronous_bios, bio);
+		queue_delayed_work(ic->commit_wq, &ic->bitmap_flush_work, 0);
+		spin_unlock_irqrestore(&ic->endio_wait.lock, flags);
+		return;
+	}
 	bio_endio(bio);
 }
 
···
 	struct dm_integrity_c *ic = container_of(work, struct dm_integrity_c, bitmap_flush_work.work);
 	struct dm_integrity_range range;
 	unsigned long limit;
+	struct bio *bio;
 
 	dm_integrity_flush_buffers(ic);
 
···
 			>> (ic->sb->log2_sectors_per_block + ic->log2_blocks_per_bitmap_bit)
 			<< (ic->sb->log2_sectors_per_block + ic->log2_blocks_per_bitmap_bit);
 	}
-	DEBUG_print("zeroing journal\n");
+	/*DEBUG_print("zeroing journal\n");*/
 	block_bitmap_op(ic, ic->journal, 0, limit, BITMAP_OP_CLEAR);
 	block_bitmap_op(ic, ic->may_write_bitmap, 0, limit, BITMAP_OP_CLEAR);
 
 	rw_journal_sectors(ic, REQ_OP_WRITE, REQ_FUA | REQ_SYNC, 0, ic->n_bitmap_blocks * (BITMAP_BLOCK_SIZE >> SECTOR_SHIFT), NULL);
 
-	remove_range(ic, &range);
+	spin_lock_irq(&ic->endio_wait.lock);
+	remove_range_unlocked(ic, &range);
+	while (unlikely((bio = bio_list_pop(&ic->synchronous_bios)) != NULL)) {
+		bio_endio(bio);
+		spin_unlock_irq(&ic->endio_wait.lock);
+		spin_lock_irq(&ic->endio_wait.lock);
+	}
+	spin_unlock_irq(&ic->endio_wait.lock);
 }
 
 
···
 		init_journal_node(&ic->journal_tree[i]);
 }
 
-static int dm_integrity_reboot(struct notifier_block *n, unsigned long code, void *x)
+static void dm_integrity_enter_synchronous_mode(struct dm_integrity_c *ic)
 {
-	struct dm_integrity_c *ic = container_of(n, struct dm_integrity_c, reboot_notifier);
+	DEBUG_print("dm_integrity_enter_synchronous_mode\n");
 
 	if (ic->mode == 'B') {
-		DEBUG_print("dm_integrity_reboot\n");
+		ic->bitmap_flush_interval = msecs_to_jiffies(10) + 1;
+		ic->synchronous_mode = 1;
+
 		cancel_delayed_work_sync(&ic->bitmap_flush_work);
 		queue_delayed_work(ic->commit_wq, &ic->bitmap_flush_work, 0);
 		flush_workqueue(ic->commit_wq);
 	}
+}
+
+static int dm_integrity_reboot(struct notifier_block *n, unsigned long code, void *x)
+{
+	struct dm_integrity_c *ic = container_of(n, struct dm_integrity_c, reboot_notifier);
+
+	DEBUG_print("dm_integrity_reboot\n");
+
+	dm_integrity_enter_synchronous_mode(ic);
 
 	return NOTIFY_DONE;
 }
···
 	ic->reboot_notifier.next = NULL;
 	ic->reboot_notifier.priority = INT_MAX - 1;	/* be notified after md and before hardware drivers */
 	WARN_ON(register_reboot_notifier(&ic->reboot_notifier));
+
+#if 0
+	dm_integrity_enter_synchronous_mode(ic);
+#endif
 }
 
 static void dm_integrity_status(struct dm_target *ti, status_type_t type,