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, 2 insertions, 13 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 5e050c1317c4..8214ba7c8bb1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -806,12 +806,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
-#ifdef CONFIG_TASK_XACCT
-        sig->rchar = sig->wchar = sig->syscr = sig->syscw = 0;
-#endif
-#ifdef CONFIG_TASK_IO_ACCOUNTING
-        memset(&sig->ioac, 0, sizeof(sig->ioac));
-#endif
+        task_io_accounting_init(&sig->ioac);
         sig->sum_sched_runtime = 0;
         INIT_LIST_HEAD(&sig->cpu_timers[0]);
         INIT_LIST_HEAD(&sig->cpu_timers[1]);
@@ -994,13 +989,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         p->last_switch_timestamp = 0;
 #endif
 
-#ifdef CONFIG_TASK_XACCT
-        p->rchar = 0;           /* I/O counter: bytes read */
-        p->wchar = 0;           /* I/O counter: bytes written */
-        p->syscr = 0;           /* I/O counter: read syscalls */
-        p->syscw = 0;           /* I/O counter: write syscalls */
-#endif
-        task_io_accounting_init(p);
+        task_io_accounting_init(&p->ioac);
         acct_clear_integrals(p);
 
         p->it_virt_expires = cputime_zero;