From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Fri, 1 Dec 2023 14:52:08 +0000 (-0500)
Subject: Fix: get_file_rcu is missing in kernels < 4.1
X-Git-Tag: v2.13.11~7
X-Git-Url: http://git.liburcu.org/?a=commitdiff_plain;h=451e062751f0574bbb33390b072f5615d084e309;p=lttng-modules.git

Fix: get_file_rcu is missing in kernels < 4.1

Open-code the get_file_rcu using atomic_long_inc_not_zero() for kernel
versions < 4.1.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I0fa905b078165ede8b1837bb8d77891d05d0e8ed
---

diff --git a/include/wrapper/fdtable.h b/include/wrapper/fdtable.h
index 9c11d02e..8b32c030 100644
--- a/include/wrapper/fdtable.h
+++ b/include/wrapper/fdtable.h
@@ -29,7 +29,7 @@ struct file *lttng_lookup_fdget_rcu(unsigned int fd)
 		return NULL;
 	return file;
 }
-#else
+#elif (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(4,1,0))
 static inline
 struct file *lttng_lookup_fdget_rcu(unsigned int fd)
 {
@@ -39,6 +39,16 @@ struct file *lttng_lookup_fdget_rcu(unsigned int fd)
 		return NULL;
 	return file;
 }
+#else
+static inline
+struct file *lttng_lookup_fdget_rcu(unsigned int fd)
+{
+	struct file* file = fcheck(fd);
+
+	if (unlikely(!file || !atomic_long_inc_not_zero(&file->f_count)))
+		return NULL;
+	return file;
+}
 #endif
 
 #if (LTTNG_LINUX_VERSION_CODE < LTTNG_KERNEL_VERSION(3,7,0))