[PATCH 5/7] IB/uverbs: increase maximum devices supported

Alex Chiang
2010-01-29T21:46:48Z

Some large systems may support more than IB_UVERBS_MAX_DEVICES
(currently 32).

This change allows us to support more devices in a backwards-compatible
manner. The first IB_UVERBS_MAX_DEVICES keep the same major/minor
device numbers that they've always had.

If there are more than IB_UVERBS_MAX_DEVICES, we then dynamically
request a new major device number (new minors start at 0).

This change increases the maximum number of HCAs to 64 (from 32).

Signed-off-by: Alex Chiang <achiang@hp.com>
---

drivers/infiniband/core/uverbs_main.c | 56 +++++++++++++++++++++++++++++----
1 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index a5d441d..0555460 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -728,6 +728,34 @@ static ssize_t show_abi_version(struct class *class, char *buf)
}
static CLASS_ATTR(abi_version, S_IRUGO, show_abi_version, NULL);

+static dev_t oflo_maj;
+static DECLARE_BITMAP(oflo_map, IB_UVERBS_MAX_DEVICES);
+
+/*
+ * If we have more than IB_UVERBS_MAX_DEVICES, dynamically overflow by
+ * requesting a new major number and doubling the number of max devices we
+ * support. It's stupid, but simple.
+ */
+static int find_oflo_devnum(void)
+{
+ int ret;
+
+ if (!oflo_maj) {
+ ret = alloc_chrdev_region(&oflo_maj, 0, IB_UVERBS_MAX_DEVICES,
+ "infiniband_verbs");
+ if (ret) {
+ printk(KERN_ERR "user_verbs: couldn't register dynamic device number\n");
+ return ret;
+ }
+ }
+
+ ret = find_first_zero_bit(oflo_map, IB_UVERBS_MAX_DEVICES);
+ if (ret >= IB_UVERBS_MAX_DEVICES)
+ return -1;
+
+ return ret;
+}
+
static void ib_uverbs_add_one(struct ib_device *device)
{
int devnum, base;
@@ -747,11 +775,19 @@ static void ib_uverbs_add_one(struct ib_device *device)
devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
if (devnum >= IB_UVERBS_MAX_DEVICES) {
spin_unlock(&map_lock);
- goto err;
+ devnum = find_oflo_devnum();
+ if (devnum < 0)
+ goto err;
+
+ spin_lock(&map_lock);
+ uverbs_dev->devnum = devnum + IB_UVERBS_MAX_DEVICES;
+ base = devnum + oflo_maj;
+ set_bit(devnum, oflo_map);
+ } else {
+ uverbs_dev->devnum = devnum;
+ base = devnum + IB_UVERBS_BASE_DEV;
+ set_bit(devnum, dev_map);
}
- uverbs_dev->devnum = devnum;
- base = devnum + IB_UVERBS_BASE_DEV;
- set_bit(devnum, dev_map);
spin_unlock(&map_lock);

uverbs_dev->ib_dev = device;
@@ -784,7 +820,10 @@ err_class:

err_cdev:
cdev_del(&uverbs_dev->cdev);
- clear_bit(devnum, dev_map);
+ if (oflo_maj)
+ clear_bit(devnum, oflo_map);
+ else
+ clear_bit(devnum, dev_map);

err:
kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);
@@ -804,7 +843,10 @@ static void ib_uverbs_remove_one(struct ib_device *device)
device_destroy(uverbs_class, uverbs_dev->cdev.dev);
cdev_del(&uverbs_dev->cdev);

- clear_bit(uverbs_dev->devnum, dev_map);
+ if (uverbs_dev->devnum < IB_UVERBS_MAX_DEVICES)
+ clear_bit(uverbs_dev->devnum, dev_map);
+ else
+ clear_bit(uverbs_dev->devnum - IB_UVERBS_MAX_DEVICES, oflo_map);

kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);
wait_for_completion(&uverbs_dev->comp);
@@ -894,6 +936,8 @@ static void __exit ib_uverbs_cleanup(void)
unregister_filesystem(&uverbs_event_fs);
class_destroy(uverbs_class);
unregister_chrdev_region(IB_UVERBS_BASE_DEV, IB_UVERBS_MAX_DEVICES);
+ if (oflo_maj)
+ unregister_chrdev_region(oflo_maj, IB_UVERBS_MAX_DEVICES);
idr_destroy(&ib_uverbs_pd_idr);
idr_destroy(&ib_uverbs_mr_idr);
idr_destroy(&ib_uverbs_mw_idr);