Revert "io/tqos: add sysctl_buffer_io_limit switch for buffer io limit."

This reverts commit 4d87de6bb4.

Revert due to refactory the buffer IO function.
In TK5, unnecessary to compatible kabi by using the "nodeinfo"
in "struct mem_cgroup {}".

Original tapd and MR:
  https://tapd.woa.com/tapd_fe/20422414/story/detail/1020422414117471502
  https://git.woa.com/tlinux/tkernel5/-/merge_requests/117

Signed-off-by: Haisu Wang <haisuwang@tencent.com>

include/linux/backing-dev.h

@@ -46,7 +46,6 @@ extern spinlock_t bdi_lock;
 extern struct list_head bdi_list;
 
 extern struct workqueue_struct *bdi_wq;
-extern unsigned int sysctl_buffer_io_limit;
 
 static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
 {
@@ -175,10 +174,7 @@ static inline bool inode_cgwb_enabled(struct inode *inode)
 {
 	struct backing_dev_info *bdi = inode_to_bdi(inode);
 
-	return (sysctl_buffer_io_limit ||
-		(cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
-		 cgroup_subsys_on_dfl(io_cgrp_subsys))) &&
-		(bdi->capabilities & BDI_CAP_WRITEBACK) &&
+	return (bdi->capabilities & BDI_CAP_WRITEBACK) &&
 		(inode->i_sb->s_iflags & SB_I_CGROUPWB);
 }
 

kernel/sysctl.c

@@ -64,7 +64,6 @@
 #include <linux/userfaultfd_k.h>
 #include <linux/pid.h>
 
-#include <linux/blkdev.h>
 #include "../lib/kstrtox.h"
 
 #include <linux/uaccess.h>
@@ -2349,15 +2348,6 @@ static struct ctl_table kern_table[] = {
 		.extra2		= SYSCTL_ONE,
 	},
 #endif
-	{
-		.procname	= "buffer_io_limit",
-		.data		= &sysctl_buffer_io_limit,
-		.maxlen		= sizeof(unsigned int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ZERO,
-		.extra2 	= SYSCTL_ONE,
-	},
 	{ }
 };
 

mm/backing-dev.c

@@ -32,9 +32,6 @@ static u64 bdi_id_cursor;
 static struct rb_root bdi_tree = RB_ROOT;
 LIST_HEAD(bdi_list);
 
-/* switch for buffer io limit */
-unsigned int sysctl_buffer_io_limit;
-
 /* bdi_wq serves all asynchronous writeback tasks */
 struct workqueue_struct *bdi_wq;