diff mbox

[dpdk-dev,v4,1/5] vhost: eventfd_link: moving ioctl to a function

Message ID 1427994080-10163-2-git-send-email-pboldin@mirantis.com (mailing list archive)
State Superseded, archived
Headers show

Commit Message

Pavel Boldin April 2, 2015, 5:01 p.m. UTC
Move ioctl `EVENTFD_COPY' handler code to an inline function.
---
 lib/librte_vhost/eventfd_link/eventfd_link.c | 171 ++++++++++++++-------------
 1 file changed, 89 insertions(+), 82 deletions(-)

Comments

Huawei Xie May 7, 2015, 7:57 a.m. UTC | #1
On 4/3/2015 1:02 AM, Pavel Boldin wrote:
> Move ioctl `EVENTFD_COPY' handler code to an inline function.
Pavel:
There is no necessity to inline this function.
/huawei
Pavel Boldin May 7, 2015, 1:16 p.m. UTC | #2
On Thu, May 7, 2015 at 10:57 AM, Xie, Huawei <huawei.xie@intel.com> wrote:

> On 4/3/2015 1:02 AM, Pavel Boldin wrote:
> > Move ioctl `EVENTFD_COPY' handler code to an inline function.
> Pavel:
> There is no necessity to inline this function.
>
Xie, there is even no necessity to split this in a five piece patchseries.
I did that solely for the purpose of clean reading.

There is no necessity to inline any single-used functions as long the
compiler is decent. But I prefer to instruct compiler to do this explictly
so there is no call/ret path in the generated code.

Pavel



> /huawei
>
Huawei Xie May 18, 2015, 6:06 a.m. UTC | #3
On 5/7/2015 9:17 PM, Pavel Boldin wrote:


On Thu, May 7, 2015 at 10:57 AM, Xie, Huawei <huawei.xie@intel.com<mailto:huawei.xie@intel.com>> wrote:
On 4/3/2015 1:02 AM, Pavel Boldin wrote:
> Move ioctl `EVENTFD_COPY' handler code to an inline function.
Pavel:
There is no necessity to inline this function.
Xie, there is even no necessity to split this in a five piece patchseries. I did that solely for the purpose of clean reading.

There is no necessity to inline any single-used functions as long the compiler is decent. But I prefer to instruct compiler to do this explictly so there is no call/ret path in the generated code.

The purpose of inline or not is not for friendly reading. inline is for performance only.
Pavel


/huawei
Pavel Boldin May 18, 2015, 9:16 a.m. UTC | #4
On Mon, May 18, 2015 at 9:06 AM, Xie, Huawei <huawei.xie@intel.com> wrote:

> On 5/7/2015 9:17 PM, Pavel Boldin wrote:
>
>
> On Thu, May 7, 2015 at 10:57 AM, Xie, Huawei <huawei.xie@intel.com<mailto:
> huawei.xie@intel.com>> wrote:
> On 4/3/2015 1:02 AM, Pavel Boldin wrote:
> > Move ioctl `EVENTFD_COPY' handler code to an inline function.
> Pavel:
> There is no necessity to inline this function.
> Xie, there is even no necessity to split this in a five piece patchseries.
> I did that solely for the purpose of clean reading.
>
> There is no necessity to inline any single-used functions as long the
> compiler is decent. But I prefer to instruct compiler to do this explictly
> so there is no call/ret path in the generated code.
>
> The purpose of inline or not is not for friendly reading. inline is for
> performance only.
>
Well, an optimizing compiler `inline's all the `static' functions that are
called only once in the file. So, this `inline' is purely for readability
of the code. This makes user aware that the function will be `inline'd
anyway.

Pavel


>
>
>
> /huawei
>
>
>
Huawei Xie June 18, 2015, 3:08 a.m. UTC | #5
Two opens here, the trivial one is i think it is not good practice to
explicitly inline non performance critical functions in c file, even if
it will be done by compiler anyway.
The critical one i have concern is whether it will introduce
inconsistency if we call fd_install on a fd that is just closed by
sys_close, because that fd will be set to next-to-be-allocated fd. I
prefer to keep the original logic in patch 4/5 if we are not clear.

As we actually don't need to use the eventfd that is allocated in user
space at all, future patch would be: directly allocate a new fd in the
kernel and call fd_install on it.
diff mbox

Patch

diff --git a/lib/librte_vhost/eventfd_link/eventfd_link.c b/lib/librte_vhost/eventfd_link/eventfd_link.c
index 62c45c8..d7cb81f 100644
--- a/lib/librte_vhost/eventfd_link/eventfd_link.c
+++ b/lib/librte_vhost/eventfd_link/eventfd_link.c
@@ -65,9 +65,8 @@  put_files_struct(struct files_struct *files)
 		BUG();
 }
 
-
-static long
-eventfd_link_ioctl(struct file *f, unsigned int ioctl, unsigned long arg)
+static inline long
+eventfd_link_ioctl_copy(unsigned long arg)
 {
 	void __user *argp = (void __user *) arg;
 	struct task_struct *task_target = NULL;
@@ -76,90 +75,98 @@  eventfd_link_ioctl(struct file *f, unsigned int ioctl, unsigned long arg)
 	struct fdtable *fdt;
 	struct eventfd_copy eventfd_copy;
 
-	switch (ioctl) {
-	case EVENTFD_COPY:
-		if (copy_from_user(&eventfd_copy, argp,
-			sizeof(struct eventfd_copy)))
-			return -EFAULT;
-
-		/*
-		 * Find the task struct for the target pid
-		 */
-		task_target =
-			pid_task(find_vpid(eventfd_copy.target_pid), PIDTYPE_PID);
-		if (task_target == NULL) {
-			pr_debug("Failed to get mem ctx for target pid\n");
-			return -EFAULT;
-		}
-
-		files = get_files_struct(current);
-		if (files == NULL) {
-			pr_debug("Failed to get files struct\n");
-			return -EFAULT;
-		}
-
-		rcu_read_lock();
-		file = fcheck_files(files, eventfd_copy.source_fd);
-		if (file) {
-			if (file->f_mode & FMODE_PATH ||
-				!atomic_long_inc_not_zero(&file->f_count))
+	if (copy_from_user(&eventfd_copy, argp,
+		sizeof(struct eventfd_copy)))
+		return -EFAULT;
+
+	/*
+	 * Find the task struct for the target pid
+	 */
+	task_target =
+		pid_task(find_vpid(eventfd_copy.target_pid), PIDTYPE_PID);
+	if (task_target == NULL) {
+		pr_debug("Failed to get mem ctx for target pid\n");
+		return -EFAULT;
+	}
+
+	files = get_files_struct(current);
+	if (files == NULL) {
+		pr_debug("Failed to get files struct\n");
+		return -EFAULT;
+	}
+
+	rcu_read_lock();
+	file = fcheck_files(files, eventfd_copy.source_fd);
+	if (file) {
+		if (file->f_mode & FMODE_PATH ||
+			!atomic_long_inc_not_zero(&file->f_count))
+			file = NULL;
+	}
+	rcu_read_unlock();
+	put_files_struct(files);
+
+	if (file == NULL) {
+		pr_debug("Failed to get file from source pid\n");
+		return 0;
+	}
+
+	/*
+	 * Release the existing eventfd in the source process
+	 */
+	spin_lock(&files->file_lock);
+	fput(file);
+	filp_close(file, files);
+	fdt = files_fdtable(files);
+	fdt->fd[eventfd_copy.source_fd] = NULL;
+	spin_unlock(&files->file_lock);
+
+	/*
+	 * Find the file struct associated with the target fd.
+	 */
+
+	files = get_files_struct(task_target);
+	if (files == NULL) {
+		pr_debug("Failed to get files struct\n");
+		return -EFAULT;
+	}
+
+	rcu_read_lock();
+	file = fcheck_files(files, eventfd_copy.target_fd);
+	if (file) {
+		if (file->f_mode & FMODE_PATH ||
+			!atomic_long_inc_not_zero(&file->f_count))
 				file = NULL;
-		}
-		rcu_read_unlock();
-		put_files_struct(files);
-
-		if (file == NULL) {
-			pr_debug("Failed to get file from source pid\n");
-			return 0;
-		}
-
-		/*
-		 * Release the existing eventfd in the source process
-		 */
-		spin_lock(&files->file_lock);
-		fput(file);
-		filp_close(file, files);
-		fdt = files_fdtable(files);
-		fdt->fd[eventfd_copy.source_fd] = NULL;
-		spin_unlock(&files->file_lock);
-
-		/*
-		 * Find the file struct associated with the target fd.
-		 */
-
-		files = get_files_struct(task_target);
-		if (files == NULL) {
-			pr_debug("Failed to get files struct\n");
-			return -EFAULT;
-		}
-
-		rcu_read_lock();
-		file = fcheck_files(files, eventfd_copy.target_fd);
-		if (file) {
-			if (file->f_mode & FMODE_PATH ||
-				!atomic_long_inc_not_zero(&file->f_count))
-					file = NULL;
-		}
-		rcu_read_unlock();
-		put_files_struct(files);
-
-		if (file == NULL) {
-			pr_debug("Failed to get file from target pid\n");
-			return 0;
-		}
-
-		/*
-		 * Install the file struct from the target process into the
-		 * file desciptor of the source process,
-		 */
-
-		fd_install(eventfd_copy.source_fd, file);
+	}
+	rcu_read_unlock();
+	put_files_struct(files);
 
+	if (file == NULL) {
+		pr_debug("Failed to get file from target pid\n");
 		return 0;
+	}
+
+	/*
+	 * Install the file struct from the target process into the
+	 * file desciptor of the source process,
+	 */
+
+	fd_install(eventfd_copy.source_fd, file);
+
+	return 0;
+}
 
-	default:
-		return -ENOIOCTLCMD;
+static long
+eventfd_link_ioctl(struct file *f, unsigned int ioctl, unsigned long arg)
+{
+	long ret = -ENOIOCTLCMD;
+
+	switch (ioctl) {
+	case EVENTFD_COPY:
+		ret = eventfd_link_ioctl_copy(arg);
+		break;
 	}
+
+	return ret;
 }
 
 static const struct file_operations eventfd_link_fops = {