video: tegra: nvmap: Fix f_count for Linux v6.13

In Linux v6.13, 'f_count' has been replaced by 'f_ref' in the 'file'
structure. Use conftest to detect if 'f_ref' is present and update the
NVMAP driver accordingly.

Please note that in most cases we can simply use the 'file_count' macro
for getting the count and this has been supported since Linux v2.6.

Bug 4991705

Change-Id: I3ccaf88bd6c3dca5b364205cf03a577945f62092
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3260939
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
GVS: buildbot_gerritrpt <buildbot_gerritrpt@nvidia.com>
Reviewed-by: Ketan Patil <ketanp@nvidia.com>
Reviewed-by: svcacv <svcacv@nvidia.com>

drivers/video/tegra/nvmap/nvmap_handle.c

@@ -495,7 +495,11 @@ found:
 		goto fail;
 	BUG_ON(!h->dmabuf->file);
 	/* This is same as get_dma_buf() if file->f_count was non-zero */
+#if defined(NV_FILE_STRUCT_HAS_F_REF) /* Linux v6.13 */
+	if (file_ref_get(&h->dmabuf->file->f_ref) == 0)
+#else
 	if (atomic_long_inc_not_zero(&h->dmabuf->file->f_count) == 0)
+#endif
 		goto fail;
 	mutex_unlock(&h->lock);
 
@@ -788,7 +792,7 @@ void nvmap_free_handle_from_fd(struct nvmap_client *client,
 	mutex_lock(&handle->lock);
 	dmabuf = is_ro ? handle->dmabuf_ro : handle->dmabuf;
 	if (dmabuf && dmabuf->file) {
-		dmabuf_ref = atomic_long_read(&dmabuf->file->f_count);
+		dmabuf_ref = file_count(dmabuf->file);
 	} else {
 		dmabuf_ref = 0;
 	}

drivers/video/tegra/nvmap/nvmap_ioctl.c

@@ -94,7 +94,7 @@ int nvmap_ioctl_getfd(struct file *filp, void __user *arg)
 	if (!ret && !IS_ERR_OR_NULL(handle)) {
 		mutex_lock(&handle->lock);
 		if (dmabuf && dmabuf->file) {
-			dmabuf_ref = atomic_long_read(&dmabuf->file->f_count);
+			dmabuf_ref = file_count(dmabuf->file);
 		} else {
 			dmabuf_ref = 0;
 		}
@@ -171,7 +171,7 @@ alloc_op_done:
 		mutex_lock(&handle->lock);
 		dmabuf = is_ro ? handle->dmabuf_ro : handle->dmabuf;
 		if (dmabuf && dmabuf->file) {
-			dmabuf_ref = atomic_long_read(&dmabuf->file->f_count);
+			dmabuf_ref = file_count(dmabuf->file);
 		} else {
 			dmabuf_ref = 0;
 		}
@@ -313,7 +313,7 @@ out:
 	if (!ret && !IS_ERR_OR_NULL(handle)) {
 		mutex_lock(&handle->lock);
 		if (dmabuf && dmabuf->file) {
-			dmabuf_ref = atomic_long_read(&dmabuf->file->f_count);
+			dmabuf_ref = file_count(dmabuf->file);
 		} else {
 			dmabuf_ref = 0;
 		}
@@ -411,7 +411,7 @@ out:
 	if (!err) {
 		mutex_lock(&handle->lock);
 		if (dmabuf && dmabuf->file) {
-			dmabuf_ref = atomic_long_read(&dmabuf->file->f_count);
+			dmabuf_ref = file_count(dmabuf->file);
 		} else {
 			dmabuf_ref = 0;
 		}
@@ -1052,7 +1052,7 @@ exit:
 		mutex_lock(&handle->lock);
 		dmabuf = is_ro ? handle->dmabuf_ro : handle->dmabuf;
 		if (dmabuf && dmabuf->file) {
-			dmabuf_ref = atomic_long_read(&dmabuf->file->f_count);
+			dmabuf_ref = file_count(dmabuf->file);
 		} else {
 			dmabuf_ref = 0;
 		}
@@ -1238,7 +1238,7 @@ out:
 	if (!ret && !IS_ERR_OR_NULL(handle))
 		trace_refcount_dup_handle(handle, dmabuf,
 				atomic_read(&handle->ref),
-				atomic_long_read(&dmabuf->file->f_count),
+				file_count(dmabuf->file),
 				is_ro ? "RO" : "RW");
 
 	if (!IS_ERR(ref))

drivers/video/tegra/nvmap/nvmap_sci_ipc.c

@@ -350,7 +350,7 @@ unlock:
 	if (!ret) {
 		mutex_lock(&h->lock);
 		if (dmabuf && dmabuf->file) {
-			dmabuf_ref = atomic_long_read(&dmabuf->file->f_count);
+			dmabuf_ref = file_count(dmabuf->file);
 		} else {
 			dmabuf_ref = 0;
 		}

scripts/conftest/Makefile

@@ -128,6 +128,7 @@ NV_CONFTEST_FUNCTION_COMPILE_TESTS += ethtool_ops_get_set_ringparam_has_ringpara
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += ethtool_ops_get_set_rxfh_has_rxfh_param_args
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += fd_empty
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += fd_file
+NV_CONFTEST_FUNCTION_COMPILE_TESTS += file_struct_has_f_ref
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += folio_entire_mapcount
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += genpd_xlate_t_has_const_of_phandle_args
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += get_file_rcu_has_double_ptr_file_arg

scripts/conftest/conftest.sh

@@ -7280,6 +7280,22 @@ compile_test() {
             compile_check_conftest "$CODE" "NV_FD_FILE_PRESENT" "" "functions"
         ;;
 
+        file_struct_has_f_ref)
+            #
+            # Determine if 'struct file' has the 'f_ref' member.
+            #
+            # Commit 90ee6ed776c0 ("fs: port files to file_ref") replaced the
+            # 'f_count' member of 'struct file' with 'f_ref' in Linux v6.13.
+            #
+            CODE="
+            #include <linux/fs.h>
+            int conftest_file_struct_has_f_ref(void) {
+                return offsetof(struct file, f_ref);
+            }"
+
+            compile_check_conftest "$CODE" "NV_FILE_STRUCT_HAS_F_REF" "" "types"
+        ;;
+
         folio_entire_mapcount)
             #
             # Determine if function folio_entire_mapcount() is present.