[PATCH v2 2/7] iommu/io-pgtable: Add refcounting for io-pgtable format modules

["Isaac J. Manjarres" <isaacm@codeaurora.org>]

In preparation for modularizing io-pgtable formats, add support
for reference counting the io-pgtable format modules to ensure
that the modules are not unloaded while they are in use.

Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
---
 drivers/iommu/io-pgtable-arm-v7s.c |  1 +
 drivers/iommu/io-pgtable-arm.c     |  5 +++++
 drivers/iommu/io-pgtable.c         | 12 ++++++++++--
 include/linux/io-pgtable.h         |  2 ++
 4 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
index 89aad2f..a5cb755a 100644
--- a/drivers/iommu/io-pgtable-arm-v7s.c
+++ b/drivers/iommu/io-pgtable-arm-v7s.c
@@ -840,6 +840,7 @@ static struct io_pgtable_init_fns io_pgtable_arm_v7s_init_fns = {
 	.fmt	= ARM_V7S,
 	.alloc	= arm_v7s_alloc_pgtable,
 	.free	= arm_v7s_free_pgtable,
+	.owner	= THIS_MODULE,
 };
 
 #ifdef CONFIG_IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index ff0ea2f..e8b1e34 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -1049,26 +1049,31 @@ static struct io_pgtable_init_fns io_pgtable_arm_lpae_init_fns[] = {
 		.fmt	= ARM_32_LPAE_S1,
 		.alloc	= arm_32_lpae_alloc_pgtable_s1,
 		.free	= arm_lpae_free_pgtable,
+		.owner	= THIS_MODULE,
 	},
 	{
 		.fmt	= ARM_32_LPAE_S2,
 		.alloc	= arm_32_lpae_alloc_pgtable_s2,
 		.free	= arm_lpae_free_pgtable,
+		.owner	= THIS_MODULE,
 	},
 	{
 		.fmt	= ARM_64_LPAE_S1,
 		.alloc	= arm_64_lpae_alloc_pgtable_s1,
 		.free	= arm_lpae_free_pgtable,
+		.owner	= THIS_MODULE,
 	},
 	{
 		.fmt	= ARM_64_LPAE_S2,
 		.alloc	= arm_64_lpae_alloc_pgtable_s2,
 		.free	= arm_lpae_free_pgtable,
+		.owner	= THIS_MODULE,
 	},
 	{
 		.fmt	= ARM_MALI_LPAE,
 		.alloc	= arm_mali_lpae_alloc_pgtable,
 		.free	= arm_lpae_free_pgtable,
+		.owner	= THIS_MODULE,
 	},
 };
 
diff --git a/drivers/iommu/io-pgtable.c b/drivers/iommu/io-pgtable.c
index 2c6eb2e..cc83542 100644
--- a/drivers/iommu/io-pgtable.c
+++ b/drivers/iommu/io-pgtable.c
@@ -10,6 +10,7 @@
 #include <linux/bug.h>
 #include <linux/io-pgtable.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/rwlock.h>
 #include <linux/slab.h>
 #include <linux/types.h>
@@ -52,9 +53,14 @@ struct io_pgtable_ops *alloc_io_pgtable_ops(enum io_pgtable_fmt fmt,
 	if (!fns)
 		return NULL;
 
+	if (!try_module_get(fns->owner))
+		return NULL;
+
 	iop = fns->alloc(cfg, cookie);
-	if (!iop)
+	if (!iop) {
+		module_put(fns->owner);
 		return NULL;
+	}
 
 	iop->fmt	= fmt;
 	iop->cookie	= cookie;
@@ -79,8 +85,10 @@ void free_io_pgtable_ops(struct io_pgtable_ops *ops)
 	iop = io_pgtable_ops_to_pgtable(ops);
 	io_pgtable_tlb_flush_all(iop);
 	fns = io_pgtable_get_init_fns(iop->fmt);
-	if (fns)
+	if (fns) {
 		fns->free(iop);
+		module_put(fns->owner);
+	}
 }
 EXPORT_SYMBOL_GPL(free_io_pgtable_ops);
 
diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
index 45b367ce..a03b262 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -169,11 +169,13 @@ struct io_pgtable_ops {
  * @fmt:   The page table format.
  * @alloc: Allocate a set of page tables described by cfg.
  * @free:  Free the page tables associated with iop.
+ * @owner: Driver module providing these ops.
  */
 struct io_pgtable_init_fns {
 	enum io_pgtable_fmt fmt;
 	struct io_pgtable *(*alloc)(struct io_pgtable_cfg *cfg, void *cookie);
 	void (*free)(struct io_pgtable *iop);
+	struct module *owner;
 };
 
 /**
-- 
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