devlink: report error once U32_MAX snapshot ids have been used

The devlink_snapshot_id_get() function returns a snapshot id. The
snapshot id is a u32, so there is no way to indicate an error code.

A future change is going to possibly add additional cases where this
function could fail. Refactor the function to return the snapshot id in
an argument, so that it can return zero or an error value.

This ensures that snapshot ids cannot be confused with error values, and
aids in the future refactor of snapshot id allocation management.

Because there is no current way to release previously used snapshot ids,
add a simple check ensuring that an error is reported in case the
snapshot_id would over flow.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/mellanox/mlx4/crdump.c b/drivers/net/ethernet/mellanox/mlx4/crdump.c
index c3f90c0f9554deb71d6468b0aa159abfb3325c3c..792951f6df0d01d0e500d7e044ce398e00272f94 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/crdump.c
+++ b/drivers/net/ethernet/mellanox/mlx4/crdump.c
@@ -169,6 +169,7 @@ int mlx4_crdump_collect(struct mlx4_dev *dev)
        struct pci_dev *pdev = dev->persist->pdev;
        unsigned long cr_res_size;
        u8 __iomem *cr_space;
+       int err;
        u32 id;
 
        if (!dev->caps.health_buffer_addrs) {
@@ -189,10 +190,14 @@ int mlx4_crdump_collect(struct mlx4_dev *dev)
                return -ENODEV;
        }
 
-       crdump_enable_crspace_access(dev, cr_space);
-
        /* Get the available snapshot ID for the dumps */
-       id = devlink_region_snapshot_id_get(devlink);
+       err = devlink_region_snapshot_id_get(devlink, &id);
+       if (err) {
+               mlx4_err(dev, "crdump: devlink get snapshot id err %d\n", err);
+               return err;
+       }
+
+       crdump_enable_crspace_access(dev, cr_space);
 
        /* Try to capture dumps */
        mlx4_crdump_collect_crspace(dev, cr_space, id);

diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c
index f7621ccb7b888b2f97ea80ed894e973a948ee0a1..609005f2ac853e4f633e52cc60d02c9e69a667fd 100644 (file)
--- a/drivers/net/netdevsim/dev.c
+++ b/drivers/net/netdevsim/dev.c
@@ -54,7 +54,11 @@ static ssize_t nsim_dev_take_snapshot_write(struct file *file,
 
        get_random_bytes(dummy_data, NSIM_DEV_DUMMY_REGION_SIZE);
 
-       id = devlink_region_snapshot_id_get(priv_to_devlink(nsim_dev));
+       err = devlink_region_snapshot_id_get(priv_to_devlink(nsim_dev), &id);
+       if (err) {
+               pr_err("Failed to get snapshot id\n");
+               return err;
+       }
        err = devlink_region_snapshot_create(nsim_dev->dummy_region,
                                             dummy_data, id);
        if (err) {

diff --git a/include/net/devlink.h b/include/net/devlink.h
index 8869ad75b9652a0ab48501ecf2338cc7c58623fc..9a46bc7fed90ef082cc1761c0ecd1714b30b0ba5 100644 (file)
--- a/include/net/devlink.h
+++ b/include/net/devlink.h
@@ -976,7 +976,7 @@ devlink_region_create(struct devlink *devlink,
                      const struct devlink_region_ops *ops,
                      u32 region_max_snapshots, u64 region_size);
 void devlink_region_destroy(struct devlink_region *region);
-u32 devlink_region_snapshot_id_get(struct devlink *devlink);
+int devlink_region_snapshot_id_get(struct devlink *devlink, u32 *id);
 int devlink_region_snapshot_create(struct devlink_region *region,
                                   u8 *data, u32 snapshot_id);
 int devlink_info_serial_number_put(struct devlink_info_req *req,

diff --git a/net/core/devlink.c b/net/core/devlink.c
index 6f07fd7a67f2c73f172fd0ee1fa0d3dea41b1a4f..8773e8f865704939283113f7662dd2e4c2588ad5 100644 (file)
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -3771,14 +3771,22 @@ out_free_msg:
 /**
  *     __devlink_region_snapshot_id_get - get snapshot ID
  *     @devlink: devlink instance
+ *     @id: storage to return snapshot id
  *
- *     Returns a new snapshot id. Must be called while holding the
- *     devlink instance lock.
+ *     Allocates a new snapshot id. Returns zero on success, or a negative
+ *     error on failure. Must be called while holding the devlink instance
+ *     lock.
  */
-static u32 __devlink_region_snapshot_id_get(struct devlink *devlink)
+static int __devlink_region_snapshot_id_get(struct devlink *devlink, u32 *id)
 {
        lockdep_assert_held(&devlink->lock);
-       return ++devlink->snapshot_id;
+
+       if (devlink->snapshot_id >= U32_MAX)
+               return -ENOSPC;
+
+       *id = ++devlink->snapshot_id;
+
+       return 0;
 }
 
 /**
@@ -7782,17 +7790,20 @@ EXPORT_SYMBOL_GPL(devlink_region_destroy);
  *     Driver should use the same id for multiple snapshots taken
  *     on multiple regions at the same time/by the same trigger.
  *
+ *     Returns zero on success, or a negative error code on failure.
+ *
  *     @devlink: devlink
+ *     @id: storage to return id
  */
-u32 devlink_region_snapshot_id_get(struct devlink *devlink)
+int devlink_region_snapshot_id_get(struct devlink *devlink, u32 *id)
 {
-       u32 id;
+       int err;
 
        mutex_lock(&devlink->lock);
-       id = __devlink_region_snapshot_id_get(devlink);
+       err = __devlink_region_snapshot_id_get(devlink, id);
        mutex_unlock(&devlink->lock);
 
-       return id;
+       return err;
 }
 EXPORT_SYMBOL_GPL(devlink_region_snapshot_id_get);