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

[Topi Miettinen]

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

Signed-off-by: Topi Miettinen <toiwo...@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