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 <dada1@cosmosbay.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index b0c6f0c3a2df..7a5fd77f8fb0 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -42,6 +42,7 @@
 #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>
@@ -113,6 +114,8 @@ static void __exit_signal(struct task_struct *tsk)
                 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. */
         }
 
@@ -1193,6 +1196,12 @@ static int wait_task_zombie(struct task_struct *p, int noreap,
                         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);
         }