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, 76 insertions, 26 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index f59318a0099..034c1ca6b33 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -505,10 +505,7 @@ struct signal_struct {
 	unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw;
 	unsigned long min_flt, maj_flt, cmin_flt, cmaj_flt;
 	unsigned long inblock, oublock, cinblock, coublock;
-#ifdef CONFIG_TASK_XACCT
-	u64 rchar, wchar, syscr, syscw;
-#endif
-	struct task_io_accounting ioac;
+	struct proc_io_accounting ioac;
 
 	/*
 	 * Cumulative ns of scheduled CPU time for dead threads in the
@@ -1256,11 +1253,7 @@ struct task_struct {
 
 	unsigned long ptrace_message;
 	siginfo_t *last_siginfo; /* For ptrace use.  */
-#ifdef CONFIG_TASK_XACCT
-/* i/o counters(bytes read/written, #syscalls */
-	u64 rchar, wchar, syscr, syscw;
-#endif
-	struct task_io_accounting ioac;
+	struct proc_io_accounting ioac;
 #if defined(CONFIG_TASK_XACCT)
 	u64 acct_rss_mem1;	/* accumulated rss usage */
 	u64 acct_vm_mem1;	/* accumulated virtual memory usage */
@@ -2190,22 +2183,22 @@ extern long sched_group_rt_period(struct task_group *tg);
 #ifdef CONFIG_TASK_XACCT
 static inline void add_rchar(struct task_struct *tsk, ssize_t amt)
 {
-	tsk->rchar += amt;
+	tsk->ioac.chr.rchar += amt;
 }
 
 static inline void add_wchar(struct task_struct *tsk, ssize_t amt)
 {
-	tsk->wchar += amt;
+	tsk->ioac.chr.wchar += amt;
 }
 
 static inline void inc_syscr(struct task_struct *tsk)
 {
-	tsk->syscr++;
+	tsk->ioac.chr.syscr++;
 }
 
 static inline void inc_syscw(struct task_struct *tsk)
 {
-	tsk->syscw++;
+	tsk->ioac.chr.syscw++;
 }
 #else
 static inline void add_rchar(struct task_struct *tsk, ssize_t amt)
diff --git a/include/linux/task_io_accounting.h b/include/linux/task_io_accounting.h
index 44d00e9ccee..165390f8b93 100644
--- a/include/linux/task_io_accounting.h
+++ b/include/linux/task_io_accounting.h
@@ -1,5 +1,5 @@
 /*
- * task_io_accounting: a structure which is used for recording a single task's
+ * proc_io_accounting: a structure which is used for recording a single task's
  * IO statistics.
  *
  * Don't include this header file directly - it is designed to be dragged in via
@@ -8,6 +8,22 @@
  * Blame akpm@osdl.org for all this.
  */
 
+#ifdef CONFIG_TASK_XACCT
+struct task_chr_io_accounting {
+	/* bytes read */
+	u64 rchar;
+	/*  bytes written */
+	u64 wchar;
+	/* # of read syscalls */
+	u64 syscr;
+	/* # of write syscalls */
+	u64 syscw;
+};
+#else /* CONFIG_TASK_XACCT */
+struct task_chr_io_accounting {
+};
+#endif /* CONFIG_TASK_XACCT */
+
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 struct task_io_accounting {
 	/*
@@ -31,7 +47,12 @@ struct task_io_accounting {
 	 */
 	u64 cancelled_write_bytes;
 };
-#else
+#else /* CONFIG_TASK_IO_ACCOUNTING */
 struct task_io_accounting {
 };
-#endif
+#endif /* CONFIG_TASK_IO_ACCOUNTING */
+
+struct proc_io_accounting {
+	struct task_chr_io_accounting chr;
+	struct task_io_accounting blk;
+};
diff --git a/include/linux/task_io_accounting_ops.h b/include/linux/task_io_accounting_ops.h
index ff46c6fad79..e6f958ebe97 100644
--- a/include/linux/task_io_accounting_ops.h
+++ b/include/linux/task_io_accounting_ops.h
@@ -9,7 +9,7 @@
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 static inline void task_io_account_read(size_t bytes)
 {
-	current->ioac.read_bytes += bytes;
+	current->ioac.blk.read_bytes += bytes;
 }
 
 /*
@@ -18,12 +18,12 @@ static inline void task_io_account_read(size_t bytes)
  */
 static inline unsigned long task_io_get_inblock(const struct task_struct *p)
 {
-	return p->ioac.read_bytes >> 9;
+	return p->ioac.blk.read_bytes >> 9;
 }
 
 static inline void task_io_account_write(size_t bytes)
 {
-	current->ioac.write_bytes += bytes;
+	current->ioac.blk.write_bytes += bytes;
 }
 
 /*
@@ -32,17 +32,25 @@ static inline void task_io_account_write(size_t bytes)
  */
 static inline unsigned long task_io_get_oublock(const struct task_struct *p)
 {
-	return p->ioac.write_bytes >> 9;
+	return p->ioac.blk.write_bytes >> 9;
 }
 
 static inline void task_io_account_cancelled_write(size_t bytes)
 {
-	current->ioac.cancelled_write_bytes += bytes;
+	current->ioac.blk.cancelled_write_bytes += bytes;
 }
 
-static inline void task_io_accounting_init(struct task_struct *tsk)
+static inline void task_io_accounting_init(struct proc_io_accounting *ioac)
 {
-	memset(&tsk->ioac, 0, sizeof(tsk->ioac));
+	memset(ioac, 0, sizeof(*ioac));
+}
+
+static inline void task_blk_io_accounting_add(struct proc_io_accounting *dst,
+						struct proc_io_accounting *src)
+{
+	dst->blk.read_bytes += src->blk.read_bytes;
+	dst->blk.write_bytes += src->blk.write_bytes;
+	dst->blk.cancelled_write_bytes += src->blk.cancelled_write_bytes;
 }
 
 #else
@@ -69,9 +77,37 @@ static inline void task_io_account_cancelled_write(size_t bytes)
 {
 }
 
-static inline void task_io_accounting_init(struct task_struct *tsk)
+static inline void task_io_accounting_init(struct proc_io_accounting *ioac)
+{
+}
+
+static inline void task_blk_io_accounting_add(struct proc_io_accounting *dst,
+						struct proc_io_accounting *src)
 {
 }
 
-#endif		/* CONFIG_TASK_IO_ACCOUNTING */
-#endif		/* __TASK_IO_ACCOUNTING_OPS_INCLUDED */
+#endif /* CONFIG_TASK_IO_ACCOUNTING */
+
+#ifdef CONFIG_TASK_XACCT
+static inline void task_chr_io_accounting_add(struct proc_io_accounting *dst,
+						struct proc_io_accounting *src)
+{
+	dst->chr.rchar += src->chr.rchar;
+	dst->chr.wchar += src->chr.wchar;
+	dst->chr.syscr += src->chr.syscr;
+	dst->chr.syscw += src->chr.syscw;
+}
+#else
+static inline void task_chr_io_accounting_add(struct proc_io_accounting *dst,
+						struct proc_io_accounting *src)
+{
+}
+#endif /* CONFIG_TASK_XACCT */
+
+static inline void task_io_accounting_add(struct proc_io_accounting *dst,
+						struct proc_io_accounting *src)
+{
+	task_chr_io_accounting_add(dst, src);
+	task_blk_io_accounting_add(dst, src);
+}
+#endif /* __TASK_IO_ACCOUNTING_OPS_INCLUDED */