drbd: refactor the backing dev max_segments calculation

Factor out a drbd_backing_dev_max_segments helper that checks the
backing device limitation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Reisner <philipp.reisner@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Tested-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Link: https://lore.kernel.org/r/20240306140332.623759-4-philipp.reisner@linbit.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 9135001a8e572d61c1984ac31e240cba03a348ab..0326b7322ceb48f566575051b1add8a2639932ce 100644 (file)
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1295,30 +1295,39 @@ static void fixup_discard_support(struct drbd_device *device, struct request_que
        }
 }
 
+/* This is the workaround for "bio would need to, but cannot, be split" */
+static unsigned int drbd_backing_dev_max_segments(struct drbd_device *device)
+{
+       unsigned int max_segments;
+
+       rcu_read_lock();
+       max_segments = rcu_dereference(device->ldev->disk_conf)->max_bio_bvecs;
+       rcu_read_unlock();
+
+       if (!max_segments)
+               return BLK_MAX_SEGMENTS;
+       return max_segments;
+}
+
 static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,
                                   unsigned int max_bio_size, struct o_qlim *o)
 {
        struct request_queue * const q = device->rq_queue;
        unsigned int max_hw_sectors = max_bio_size >> 9;
-       unsigned int max_segments = 0;
+       unsigned int max_segments = BLK_MAX_SEGMENTS;
        struct request_queue *b = NULL;
-       struct disk_conf *dc;
 
        if (bdev) {
                b = bdev->backing_bdev->bd_disk->queue;
 
                max_hw_sectors = min(queue_max_hw_sectors(b), max_bio_size >> 9);
-               rcu_read_lock();
-               dc = rcu_dereference(device->ldev->disk_conf);
-               max_segments = dc->max_bio_bvecs;
-               rcu_read_unlock();
+               max_segments = drbd_backing_dev_max_segments(device);
 
                blk_set_stacking_limits(&q->limits);
        }
 
        blk_queue_max_hw_sectors(q, max_hw_sectors);
-       /* This is the workaround for "bio would need to, but cannot, be split" */
-       blk_queue_max_segments(q, max_segments ? max_segments : BLK_MAX_SEGMENTS);
+       blk_queue_max_segments(q, max_segments);
        blk_queue_segment_boundary(q, PAGE_SIZE-1);
        decide_on_discard_support(device, bdev);