[RFC 05/18] limits: track and present RLIMIT_NOFILE actual max

[Topi Miettinen <toiwoton@gmail.com>]

Track maximum number of files for the process, present current maximum
in /proc/self/limits.

Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
---
 fs/file.c             |  4 ++++
 fs/proc/base.c        | 10 ++++++----
 include/linux/sched.h |  7 +++++++
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index 6b1acdf..2d0d206 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -547,6 +547,8 @@ repeat:
 	}
 #endif
 
+	bump_rlimit(RLIMIT_NOFILE, fd);
+
 out:
 	spin_unlock(&files->file_lock);
 	return error;
@@ -857,6 +859,8 @@ __releases(&files->file_lock)
 	if (tofree)
 		filp_close(tofree, files);
 
+	bump_rlimit(RLIMIT_NOFILE, fd);
+
 	return fd;
 
 Ebusy:
diff --git a/fs/proc/base.c b/fs/proc/base.c
index a11eb71..227997b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -630,8 +630,8 @@ static int proc_pid_limits(struct seq_file *m, struct pid_namespace *ns,
 	/*
 	 * print the file header
 	 */
-       seq_printf(m, "%-25s %-20s %-20s %-10s\n",
-		  "Limit", "Soft Limit", "Hard Limit", "Units");
+	seq_printf(m, "%-25s %-20s %-20s %-10s %-20s\n",
+		   "Limit", "Soft Limit", "Hard Limit", "Units", "Max");
 
 	for (i = 0; i < RLIM_NLIMITS; i++) {
 		if (rlim[i].rlim_cur == RLIM_INFINITY)
@@ -647,9 +647,11 @@ static int proc_pid_limits(struct seq_file *m, struct pid_namespace *ns,
 			seq_printf(m, "%-20lu ", rlim[i].rlim_max);
 
 		if (lnames[i].unit)
-			seq_printf(m, "%-10s\n", lnames[i].unit);
+			seq_printf(m, "%-10s", lnames[i].unit);
 		else
-			seq_putc(m, '\n');
+			seq_printf(m, "%-10s", "");
+		seq_printf(m, "%-20lu\n",
+			   task->signal->rlim_curmax[i]);
 	}
 
 	return 0;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9c48a08..0150380 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -782,6 +782,7 @@ struct signal_struct {
 	 * have no need to disable irqs.
 	 */
 	struct rlimit rlim[RLIM_NLIMITS];
+	unsigned long rlim_curmax[RLIM_NLIMITS];
 
 #ifdef CONFIG_BSD_PROCESS_ACCT
 	struct pacct_struct pacct;	/* per-process accounting information */
@@ -3376,6 +3377,12 @@ static inline unsigned long rlimit_max(unsigned int limit)
 	return task_rlimit_max(current, limit);
 }
 
+static inline void bump_rlimit(unsigned int limit, unsigned long r)
+{
+	if (READ_ONCE(current->signal->rlim_curmax[limit]) < r)
+		current->signal->rlim_curmax[limit] = r;
+}
+
 #ifdef CONFIG_CPU_FREQ
 struct update_util_data {
 	void (*func)(struct update_util_data *data,
-- 
2.8.1