getrusage(): fill ru_inblock and ru_oublock fields if possible

If CONFIG_TASK_IO_ACCOUNTING is defined, we update io accounting counters for
each task.

This patch permits reporting of values using the well known getrusage()
syscall, filling ru_inblock and ru_oublock instead of null values.

As TASK_IO_ACCOUNTING currently counts bytes counts, we approximate blocks
count doing : nr_blocks = nr_bytes / 512

Example of use :
----------------------
After patch is applied, /usr/bin/time command can now give a good
approximation of IO that the process had to do.

$ /usr/bin/time grep tototo /usr/include/*
Command exited with non-zero status 1
0.00user 0.02system 0:02.11elapsed 1%CPU (0avgtext+0avgdata 0maxresident)k
24288inputs+0outputs (0major+259minor)pagefaults 0swaps

$ /usr/bin/time dd if=/dev/zero of=/tmp/testfile count=1000
1000+0 enregistrements lus
1000+0 enregistrements écrits
512000 octets (512 kB) copiés, 0,00326601 seconde, 157 MB/s
0.00user 0.00system 0:00.00elapsed 80%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+3000outputs (0major+299minor)pagefaults 0swaps

Signed-off-by: Eric Dumazet <[e-mail]>
Cc: Oleg Nesterov <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/sched.h

···
 	cputime_t utime, stime, cutime, cstime;
 	unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw;
 	unsigned long min_flt, maj_flt, cmin_flt, cmaj_flt;
+	unsigned long inblock, oublock, cinblock, coublock;
 
 	/*
 	 * Cumulative ns of scheduled CPU time for dead threads in the

include/linux/task_io_accounting_ops.h

···
 	current->ioac.read_bytes += bytes;
 }
 
+/*
+ * We approximate number of blocks, because we account bytes only.
+ * A 'block' is 512 bytes
+ */
+static inline unsigned long task_io_get_inblock(const struct task_struct *p)
+{
+	return p->ioac.read_bytes >> 9;
+}
+
 static inline void task_io_account_write(size_t bytes)
 {
 	current->ioac.write_bytes += bytes;
+}
+
+/*
+ * We approximate number of blocks, because we account bytes only.
+ * A 'block' is 512 bytes
+ */
+static inline unsigned long task_io_get_oublock(const struct task_struct *p)
+{
+	return p->ioac.write_bytes >> 9;
 }
 
 static inline void task_io_account_cancelled_write(size_t bytes)
···
 {
 }
 
+static inline unsigned long task_io_get_inblock(const struct task_struct *p)
+{
+	return 0;
+}
+
 static inline void task_io_account_write(size_t bytes)
 {
+}
+
+static inline unsigned long task_io_get_oublock(const struct task_struct *p)
+{
+	return 0;
 }
 
 static inline void task_io_account_cancelled_write(size_t bytes)

kernel/exit.c

···
 #include <linux/audit.h> /* for audit_free() */
 #include <linux/resource.h>
 #include <linux/blkdev.h>
+#include <linux/task_io_accounting_ops.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
···
 		sig->nvcsw += tsk->nvcsw;
 		sig->nivcsw += tsk->nivcsw;
 		sig->sched_time += tsk->sched_time;
+		sig->inblock += task_io_get_inblock(tsk);
+		sig->oublock += task_io_get_oublock(tsk);
 		sig = NULL; /* Marker for below. */
 	}
 
···
 			p->nvcsw + sig->nvcsw + sig->cnvcsw;
 		psig->cnivcsw +=
 			p->nivcsw + sig->nivcsw + sig->cnivcsw;
+		psig->cinblock +=
+			task_io_get_inblock(p) +
+			sig->inblock + sig->cinblock;
+		psig->coublock +=
+			task_io_get_oublock(p) +
+			sig->oublock + sig->coublock;
 		spin_unlock_irq(&p->parent->sighand->siglock);
 	}
 

kernel/fork.c

···
 	sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 	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;
 	sig->sched_time = 0;
 	INIT_LIST_HEAD(&sig->cpu_timers[0]);
 	INIT_LIST_HEAD(&sig->cpu_timers[1]);

kernel/sys.c

···
 #include <linux/signal.h>
 #include <linux/cn_proc.h>
 #include <linux/getcpu.h>
+#include <linux/task_io_accounting_ops.h>
 
 #include <linux/compat.h>
 #include <linux/syscalls.h>
···
 			r->ru_nivcsw = p->signal->cnivcsw;
 			r->ru_minflt = p->signal->cmin_flt;
 			r->ru_majflt = p->signal->cmaj_flt;
+			r->ru_inblock = p->signal->cinblock;
+			r->ru_oublock = p->signal->coublock;
 
 			if (who == RUSAGE_CHILDREN)
 				break;
···
 			r->ru_nivcsw += p->signal->nivcsw;
 			r->ru_minflt += p->signal->min_flt;
 			r->ru_majflt += p->signal->maj_flt;
+			r->ru_inblock += p->signal->inblock;
+			r->ru_oublock += p->signal->oublock;
 			t = p;
 			do {
 				utime = cputime_add(utime, t->utime);
···
 				r->ru_nivcsw += t->nivcsw;
 				r->ru_minflt += t->min_flt;
 				r->ru_majflt += t->maj_flt;
+				r->ru_inblock += task_io_get_inblock(t);
+				r->ru_oublock += task_io_get_oublock(t);
 				t = next_thread(t);
 			} while (t != p);
 			break;