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>

3 files changed, 12 insertions, 47 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 0caf590548a0..eb4d6470d1d0 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -121,18 +121,7 @@ static void __exit_signal(struct task_struct *tsk)
                 sig->nivcsw += tsk->nivcsw;
                 sig->inblock += task_io_get_inblock(tsk);
                 sig->oublock += task_io_get_oublock(tsk);
-#ifdef CONFIG_TASK_XACCT
-                sig->rchar += tsk->rchar;
-                sig->wchar += tsk->wchar;
-                sig->syscr += tsk->syscr;
-                sig->syscw += tsk->syscw;
-#endif /* CONFIG_TASK_XACCT */
-#ifdef CONFIG_TASK_IO_ACCOUNTING
-                sig->ioac.read_bytes += tsk->ioac.read_bytes;
-                sig->ioac.write_bytes += tsk->ioac.write_bytes;
-                sig->ioac.cancelled_write_bytes +=
-                                        tsk->ioac.cancelled_write_bytes;
-#endif /* CONFIG_TASK_IO_ACCOUNTING */
+                task_io_accounting_add(&sig->ioac, &tsk->ioac);
                 sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
                 sig = NULL; /* Marker for below. */
         }
@@ -1363,21 +1352,8 @@ static int wait_task_zombie(struct task_struct *p, int options,
                 psig->coublock +=
                         task_io_get_oublock(p) +
                         sig->oublock + sig->coublock;
-#ifdef CONFIG_TASK_XACCT
-                psig->rchar += p->rchar + sig->rchar;
-                psig->wchar += p->wchar + sig->wchar;
-                psig->syscr += p->syscr + sig->syscr;
-                psig->syscw += p->syscw + sig->syscw;
-#endif /* CONFIG_TASK_XACCT */
-#ifdef CONFIG_TASK_IO_ACCOUNTING
-                psig->ioac.read_bytes +=
-                        p->ioac.read_bytes + sig->ioac.read_bytes;
-                psig->ioac.write_bytes +=
-                        p->ioac.write_bytes + sig->ioac.write_bytes;
-                psig->ioac.cancelled_write_bytes +=
-                                p->ioac.cancelled_write_bytes +
-                                sig->ioac.cancelled_write_bytes;
-#endif /* CONFIG_TASK_IO_ACCOUNTING */
+                task_io_accounting_add(&psig->ioac, &p->ioac);
+                task_io_accounting_add(&psig->ioac, &sig->ioac);
                 spin_unlock_irq(&p->parent->sighand->siglock);
         }
 
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;
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index 3da47ccdc5e5..f9cd2561689c 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -94,14 +94,14 @@ void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
                 stats->hiwater_vm    = mm->hiwater_vm * PAGE_SIZE / KB;
                 mmput(mm);
         }
-        stats->read_char        = p->rchar;
-        stats->write_char       = p->wchar;
-        stats->read_syscalls    = p->syscr;
-        stats->write_syscalls   = p->syscw;
+        stats->read_char        = p->ioac.chr.rchar;
+        stats->write_char       = p->ioac.chr.wchar;
+        stats->read_syscalls    = p->ioac.chr.syscr;
+        stats->write_syscalls   = p->ioac.chr.syscw;
 #ifdef CONFIG_TASK_IO_ACCOUNTING
-        stats->read_bytes       = p->ioac.read_bytes;
-        stats->write_bytes      = p->ioac.write_bytes;
-        stats->cancelled_write_bytes = p->ioac.cancelled_write_bytes;
+        stats->read_bytes       = p->ioac.blk.read_bytes;
+        stats->write_bytes      = p->ioac.blk.write_bytes;
+        stats->cancelled_write_bytes = p->ioac.blk.cancelled_write_bytes;
 #else
         stats->read_bytes       = 0;
         stats->write_bytes      = 0;