[RFC PATCH 4/5] fs/proc: Introduce /proc/all/io

[Eugene Lubarsky <elubarsky.linux@xxxxxxxxx>]

Returns io info for all visible processes.

The data is the same as /proc/[pid]/io but formatted as a series
of numbers on a single line. A PID column is also prepended.

Signed-off-by: Eugene Lubarsky <elubarsky.linux@xxxxxxxxx>
---
 fs/proc/base.c | 66 ++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 59 insertions(+), 7 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 5982fd43dd21..03d48225b6d1 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2910,9 +2910,8 @@ static const struct file_operations proc_coredump_filter_operations = {
 #endif
 
 #ifdef CONFIG_TASK_IO_ACCOUNTING
-static int do_io_accounting(struct task_struct *task, struct seq_file *m, int whole)
+static int calc_io_accounting(struct task_struct *task, struct task_io_accounting *acct, int whole)
 {
-	struct task_io_accounting acct = task->ioac;
 	unsigned long flags;
 	int result;
 
@@ -2928,12 +2927,27 @@ static int do_io_accounting(struct task_struct *task, struct seq_file *m, int wh
 	if (whole && lock_task_sighand(task, &flags)) {
 		struct task_struct *t = task;
 
-		task_io_accounting_add(&acct, &task->signal->ioac);
+		task_io_accounting_add(acct, &task->signal->ioac);
 		while_each_thread(task, t)
-			task_io_accounting_add(&acct, &t->ioac);
+			task_io_accounting_add(acct, &t->ioac);
 
 		unlock_task_sighand(task, &flags);
 	}
+	result = 0;
+
+out_unlock:
+	mutex_unlock(&task->signal->exec_update_mutex);
+	return result;
+}
+static int do_io_accounting(struct task_struct *task, struct seq_file *m, int whole)
+{
+	struct task_io_accounting acct = task->ioac;
+	int result;
+
+	result = calc_io_accounting(task, &acct, whole);
+	if (result)
+		return result;
+
 	seq_printf(m,
 		   "rchar: %llu\n"
 		   "wchar: %llu\n"
@@ -2949,10 +2963,7 @@ static int do_io_accounting(struct task_struct *task, struct seq_file *m, int wh
 		   (unsigned long long)acct.read_bytes,
 		   (unsigned long long)acct.write_bytes,
 		   (unsigned long long)acct.cancelled_write_bytes);
-	result = 0;
 
-out_unlock:
-	mutex_unlock(&task->signal->exec_update_mutex);
 	return result;
 }
 
@@ -3896,7 +3907,42 @@ static int proc_all_statm(struct seq_file *m, void *v)
 	return proc_pid_statm(m, ns, pid, task);
 }
 
+#ifdef CONFIG_TASK_IO_ACCOUNTING
+static int proc_all_io_print_one(struct seq_file *m, struct task_struct *task)
+{
+	struct task_io_accounting acct = task->ioac;
+	int result;
 
+	result = calc_io_accounting(task, &acct, 1);
+	if (result)
+		return result;
+
+	seq_printf(m,
+		   "%llu %llu %llu %llu %llu %llu %llu\n",
+		   (unsigned long long)acct.rchar,
+		   (unsigned long long)acct.wchar,
+		   (unsigned long long)acct.syscr,
+		   (unsigned long long)acct.syscw,
+		   (unsigned long long)acct.read_bytes,
+		   (unsigned long long)acct.write_bytes,
+		   (unsigned long long)acct.cancelled_write_bytes);
+
+	return result;
+}
+
+static int proc_all_io(struct seq_file *m, void *v)
+{
+	struct all_iter *iter = (struct all_iter *) v;
+	struct pid_namespace *ns = iter->ns;
+	struct task_struct *task = iter->tgid_iter.task;
+	struct pid *pid = task->thread_pid;
+
+	seq_put_decimal_ull(m, "", pid_nr_ns(pid, ns));
+	seq_puts(m, " ");
+
+	return proc_all_io_print_one(m, task);
+}
+#endif
 
 static int proc_all_status(struct seq_file *m, void *v)
 {
@@ -3915,6 +3961,9 @@ static int proc_all_status(struct seq_file *m, void *v)
 PROC_ALL_OPS(stat);
 PROC_ALL_OPS(statm);
 PROC_ALL_OPS(status);
+#ifdef CONFIG_TASK_IO_ACCOUNTING
+	PROC_ALL_OPS(io);
+#endif
 
 #define PROC_ALL_CREATE(NAME) \
 	do { \
@@ -3932,4 +3981,7 @@ void __init proc_all_init(void)
 	PROC_ALL_CREATE(stat);
 	PROC_ALL_CREATE(statm);
 	PROC_ALL_CREATE(status);
+#ifdef CONFIG_TASK_IO_ACCOUNTING
+	PROC_ALL_CREATE(io);
+#endif
 }
-- 
2.25.1