[PATCH v2 11/13] libmultipath: Add support for block device IOCTL

[John Garry <john.g.garry@oracle.com>]

Add mpath_bdev_ioctl() as a multipath block device IOCTL handler. This
handler calls into the mpath_device bdev fops handler.

Like what is done for cdev IOCTL handler, use .ioctl_begin and
.ioctl_finish methods to know when the until the SRCU read lock - this is
for special NVMe controller IOCTL handling.

The .compat_ioctl handler is given the standard handler.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 lib/multipath.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/lib/multipath.c b/lib/multipath.c
index c72f35e02e2ab..e2998c1b277c0 100644
--- a/lib/multipath.c
+++ b/lib/multipath.c
@@ -490,6 +490,38 @@ static void mpath_bdev_release(struct gendisk *disk)
 	mpath_put_head(mpath_head);
 }
 
+static int mpath_bdev_ioctl(struct block_device *bdev, blk_mode_t mode,
+		    unsigned int cmd, unsigned long arg)
+{
+	struct gendisk *disk = bdev->bd_disk;
+	struct mpath_head *mpath_head = mpath_gendisk_to_head(disk);
+	struct mpath_device *mpath_device;
+	int srcu_idx, err;
+	void *unlocked_ioctl_data = NULL;
+
+	srcu_idx = srcu_read_lock(&mpath_head->srcu);
+	mpath_device = mpath_find_path(mpath_head);
+	if (!mpath_device) {
+		err = -EWOULDBLOCK;
+		goto out_unlock;
+	}
+
+	if (mpath_head->mpdt->ioctl_begin)
+		mpath_head->mpdt->ioctl_begin(mpath_device, cmd,
+					&unlocked_ioctl_data);
+	if (unlocked_ioctl_data)
+		srcu_read_unlock(&mpath_head->srcu, srcu_idx);
+	err = mpath_device->disk->fops->ioctl(
+			mpath_device->disk->part0, mode, cmd, arg);
+	if (unlocked_ioctl_data) {
+		mpath_head->mpdt->ioctl_finish(unlocked_ioctl_data);
+		return err;
+	}
+out_unlock:
+	srcu_read_unlock(&mpath_head->srcu, srcu_idx);
+	return err;
+}
+
 static int mpath_pr_register(struct block_device *bdev, u64 old_key,
 			u64 new_key, unsigned int flags)
 {
@@ -676,6 +708,8 @@ const struct block_device_operations mpath_ops = {
 	.open		= mpath_bdev_open,
 	.release	= mpath_bdev_release,
 	.submit_bio	= mpath_bdev_submit_bio,
+	.ioctl		= mpath_bdev_ioctl,
+	.compat_ioctl	= blkdev_compat_ptr_ioctl,
 	.report_zones	= mpath_bdev_report_zones,
 	.pr_ops		= &mpath_pr_ops,
 };
-- 
2.43.5