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, 7 insertions, 0 deletions

diff --git a/kernel/sys.c b/kernel/sys.c
index cdb7e9457ba6..ec319bbb0bd4 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -29,6 +29,7 @@
 #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>
@@ -2082,6 +2083,8 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
                         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;
@@ -2093,6 +2096,8 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
                         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);
@@ -2101,6 +2106,8 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
                                 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;