task IO accounting: improve code readability

Put all i/o statistics in struct proc_io_accounting and use inline functions to
initialize and increment statistics, removing a lot of single variable
assignments.

This also reduces the kernel size as following (with CONFIG_TASK_XACCT=y and
CONFIG_TASK_IO_ACCOUNTING=y).

    text    data     bss     dec     hex filename
   11651       0       0   11651    2d83 kernel/exit.o.before
   11619       0       0   11619    2d63 kernel/exit.o.after
   10886     132     136   11154    2b92 kernel/fork.o.before
   10758     132     136   11026    2b12 kernel/fork.o.after

 3082029  807968 4818600 8708597  84e1f5 vmlinux.o.before
 3081869  807968 4818600 8708437  84e155 vmlinux.o.after

Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 41 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index e74308bdabd3..3d94906c7aa8 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -53,6 +53,7 @@
 #include <linux/time.h>
 #include <linux/proc_fs.h>
 #include <linux/stat.h>
+#include <linux/task_io_accounting_ops.h>
 #include <linux/init.h>
 #include <linux/capability.h>
 #include <linux/file.h>
@@ -2402,44 +2403,17 @@ static int proc_base_fill_cache(struct file *filp, void *dirent,
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 static int do_io_accounting(struct task_struct *task, char *buffer, int whole)
 {
-        u64 rchar, wchar, syscr, syscw;
-        struct task_io_accounting ioac;
-
-        rchar = task->rchar;
-        wchar = task->wchar;
-        syscr = task->syscr;
-        syscw = task->syscw;
-        memcpy(&ioac, &task->ioac, sizeof(ioac));
-
-        if (whole) {
-                unsigned long flags;
-
-                if (lock_task_sighand(task, &flags)) {
-                        struct signal_struct *sig = task->signal;
-                        struct task_struct *t = task;
-
-                        rchar += sig->rchar;
-                        wchar += sig->wchar;
-                        syscr += sig->syscr;
-                        syscw += sig->syscw;
-
-                        ioac.read_bytes += sig->ioac.read_bytes;
-                        ioac.write_bytes += sig->ioac.write_bytes;
-                        ioac.cancelled_write_bytes +=
-                                        sig->ioac.cancelled_write_bytes;
-                        while_each_thread(task, t) {
-                                rchar += t->rchar;
-                                wchar += t->wchar;
-                                syscr += t->syscr;
-                                syscw += t->syscw;
-
-                                ioac.read_bytes += t->ioac.read_bytes;
-                                ioac.write_bytes += t->ioac.write_bytes;
-                                ioac.cancelled_write_bytes +=
-                                        t->ioac.cancelled_write_bytes;
-                        }
-                        unlock_task_sighand(task, &flags);
-                }
+        struct proc_io_accounting acct = task->ioac;
+        unsigned long flags;
+
+        if (whole && lock_task_sighand(task, &flags)) {
+                struct task_struct *t = task;
+
+                task_io_accounting_add(&acct, &task->signal->ioac);
+                while_each_thread(task, t)
+                        task_io_accounting_add(&acct, &t->ioac);
+
+                unlock_task_sighand(task, &flags);
         }
         return sprintf(buffer,
                         "rchar: %llu\n"
@@ -2449,9 +2423,10 @@ static int do_io_accounting(struct task_struct *task, char *buffer, int whole)
                         "read_bytes: %llu\n"
                         "write_bytes: %llu\n"
                         "cancelled_write_bytes: %llu\n",
-                        rchar, wchar, syscr, syscw,
-                        ioac.read_bytes, ioac.write_bytes,
-                        ioac.cancelled_write_bytes);
+                        acct.chr.rchar, acct.chr.wchar,
+                        acct.chr.syscr, acct.chr.syscw,
+                        acct.blk.read_bytes, acct.blk.write_bytes,
+                        acct.blk.cancelled_write_bytes);
 }
 
 static int proc_tid_io_accounting(struct task_struct *task, char *buffer)