cgroup/files: support boot parameter to control if disable files cgroup

hulk inclusion
category: bugfix
bugzilla: NA
CVE: NA

--------------------------------

When files cgroup is enabled, it's will leads syscall performance
regression in UnixBench. Add a helper files_cgroup_enabled() and
use it to control if use files cgroup, wen can use cgroup_disable=files
in cmdline to disable files cgroup.

syscall of UnixBench (large is better)
enable files cgroup:            2868.5
disable files cgroup:           3177.0
disable config of files cgroup: 3186.5
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NTao Hou <houtao1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -488,9 +488,10 @@
 			  a single hierarchy
 			- foo isn't visible as an individually mountable
 			  subsystem
-			{Currently only "memory" controller deal with this and
-			cut the overhead, others just disable the usage. So
-			only cgroup_disable=memory is actually worthy}
+			{Currently "memory" and "files" controller deal with
+			this and cut the overhead, others just disable the usage.
+			So cgroup_disable=memory and cgroup_disable=files are
+			actually worthy}
 
 	cgroup_no_v1=	[KNL] Disable one, multiple, all cgroup controllers in v1
 			Format: { controller[,controller...] | "all" }

fs/file.c

@@ -295,7 +295,8 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 	new_fdt->full_fds_bits = newf->full_fds_bits_init;
 	new_fdt->fd = &newf->fd_array[0];
 #ifdef CONFIG_CGROUP_FILES
-	files_cgroup_assign(newf);
+	if (files_cgroup_enabled())
+		files_cgroup_assign(newf);
 #endif
 
 	spin_lock(&oldf->file_lock);
@@ -361,6 +362,8 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 
 	rcu_assign_pointer(newf->fdt, new_fdt);
 #ifdef CONFIG_CGROUP_FILES
+	if (!files_cgroup_enabled())
+		return newf;
 	spin_lock(&newf->file_lock);
 	if (!files_cgroup_alloc_fd(newf, files_cgroup_count_fds(newf))) {
 		spin_unlock(&newf->file_lock);
@@ -385,7 +388,8 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 
 out_release:
 #ifdef CONFIG_CGROUP_FILES
-	files_cgroup_remove(newf);
+	if (files_cgroup_enabled())
+		files_cgroup_remove(newf);
 #endif
 	kmem_cache_free(files_cachep, newf);
 out:
@@ -413,7 +417,8 @@ static struct fdtable *close_files(struct files_struct * files)
 				struct file * file = xchg(&fdt->fd[i], NULL);
 				if (file) {
 #ifdef CONFIG_CGROUP_FILES
-					files_cgroup_unalloc_fd(files, 1);
+					if (files_cgroup_enabled())
+						files_cgroup_unalloc_fd(files, 1);
 #endif
 					filp_close(file, files);
 					cond_resched();
@@ -424,7 +429,8 @@ static struct fdtable *close_files(struct files_struct * files)
 		}
 	}
 #ifdef CONFIG_CGROUP_FILES
-	files_cgroup_remove(files);
+	if (files_cgroup_enabled())
+		files_cgroup_remove(files);
 #endif
 
 	return fdt;
@@ -546,7 +552,7 @@ int __alloc_fd(struct files_struct *files,
 	if (error)
 		goto repeat;
 #ifdef CONFIG_CGROUP_FILES
-	if (files_cgroup_alloc_fd(files, 1)) {
+	if (files_cgroup_enabled() && files_cgroup_alloc_fd(files, 1)) {
 		error = -EMFILE;
 		goto out;
 	}
@@ -594,7 +600,7 @@ static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 {
 	struct fdtable *fdt = files_fdtable(files);
 #ifdef CONFIG_CGROUP_FILES
-	if (test_bit(fd, fdt->open_fds))
+	if (files_cgroup_enabled() && test_bit(fd, fdt->open_fds))
 		files_cgroup_unalloc_fd(files, 1);
 #endif
 	__clear_open_fd(fd, fdt);
@@ -919,7 +925,8 @@ __releases(&files->file_lock)
 		goto out;
 	}
 #ifdef CONFIG_CGROUP_FILES
-	if (!tofree && files_cgroup_alloc_fd(files, 1)) {
+	if (files_cgroup_enabled() &&
+	    !tofree && files_cgroup_alloc_fd(files, 1)) {
 		err = -EMFILE;
 		goto out;
 	}

include/linux/filescontrol.h

@@ -19,6 +19,7 @@
 #define _LINUX_FILESCONTROL_H
 
 #include <linux/fdtable.h>
+#include <linux/cgroup.h>
 
 #ifdef CONFIG_CGROUP_FILES
 
@@ -30,5 +31,10 @@ extern struct files_struct init_files;
 void files_cgroup_assign(struct files_struct *files);
 void files_cgroup_remove(struct files_struct *files);
 
+static inline bool files_cgroup_enabled(void)
+{
+	return cgroup_subsys_enabled(files_cgrp_subsys);
+}
+
 #endif /* CONFIG_CGROUP_FILES */
 #endif /* _LINUX_FILESCONTROL_H */