[RFC PATCH v2 12/22] devlink: convert snapshot id getter to return an error

[Jacob Keller <jacob.e.keller@intel.com>]

Modify the devlink_snapshot_id_get function to return a signed value,
enabling reporting an error on failure.

This enables easily refactoring how IDs are generated and kept track of
in the future. For now, just report ENOSPC once INT_MAX snapshot ids
have been returned.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
---
 drivers/net/ethernet/mellanox/mlx4/crdump.c | 10 +++++++---
 drivers/net/netdevsim/dev.c                 |  7 +++++--
 include/net/devlink.h                       |  2 +-
 net/core/devlink.c                          | 16 +++++++++++-----
 4 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/crdump.c b/drivers/net/ethernet/mellanox/mlx4/crdump.c
index c3f90c0f9554..723a66efdf32 100644
--- a/drivers/net/ethernet/mellanox/mlx4/crdump.c
+++ b/drivers/net/ethernet/mellanox/mlx4/crdump.c
@@ -169,7 +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;
-	u32 id;
+	int id;
 
 	if (!dev->caps.health_buffer_addrs) {
 		mlx4_info(dev, "crdump: FW doesn't support health buffer access, skipping\n");
@@ -189,10 +189,14 @@ 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);
+	if (id < 0) {
+		mlx4_err(dev, "crdump: devlink get snapshot id err %d\n", id);
+		return id;
+	}
+
+	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 5b1ba67fd4a0..e30bd94c3d52 100644
--- a/drivers/net/netdevsim/dev.c
+++ b/drivers/net/netdevsim/dev.c
@@ -44,8 +44,7 @@ static ssize_t nsim_dev_take_snapshot_write(struct file *file,
 {
 	struct nsim_dev *nsim_dev = file->private_data;
 	void *dummy_data;
-	int err;
-	u32 id;
+	int err, id;
 
 	dummy_data = kmalloc(NSIM_DEV_DUMMY_REGION_SIZE, GFP_KERNEL);
 	if (!dummy_data)
@@ -54,6 +53,10 @@ 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));
+	if (id < 0) {
+		pr_err("Failed to get snapshot id\n");
+		return id;
+	}
 	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 437d3f51a5ab..3a7759355434 100644
--- a/include/net/devlink.h
+++ b/include/net/devlink.h
@@ -962,7 +962,7 @@ 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);
 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 0e94887713f4..da4e669f425b 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -3764,12 +3764,16 @@ static void devlink_nl_region_notify(struct devlink_region *region,
  *	__devlink_region_snapshot_id_get - get snapshot ID
  *	@devlink: devlink instance
  *
- *	Returns a new snapshot id. Must be called while holding the
- *	devlink instance lock.
+ *	Returns a new snapshot id or a negative error code 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)
 {
 	lockdep_assert_held(&devlink->lock);
+
+	if (devlink->snapshot_id >= INT_MAX)
+		return -ENOSPC;
+
 	return ++devlink->snapshot_id;
 }
 
@@ -7670,11 +7674,13 @@ 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 a positive id or a negative error code on failure.
+ *
  *	@devlink: devlink
  */
-u32 devlink_region_snapshot_id_get(struct devlink *devlink)
+int devlink_region_snapshot_id_get(struct devlink *devlink)
 {
-	u32 id;
+	int id;
 
 	mutex_lock(&devlink->lock);
 	id = __devlink_region_snapshot_id_get(devlink);
-- 
2.25.0.368.g28a2d05eebfb