commit 3eb39f47934f9d5a3027fe00d906a45fe3a15fad
Author: 3eb39f47934f9d5a3027fe00d906a45fe3a15fadcommit 25afba4499ac93a41721fcb25eed1905f85d06fc (HEAD -> work, origin/work)
Author: Christian Brauner <christian@brauner.io>
Date:   Wed Mar 20 08:05:54 2019 +0100

    pidfd: introduce "pidfd" proc file

    Signed-off-by: Christian Brauner <christian@brauner.io>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index ddef482f1334..081c57988fd6 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -357,6 +357,9 @@ static const struct file_operations proc_pid_cmdline_ops = {
        .llseek = generic_file_llseek,
 };

+static const struct file_operations proc_pid_pidfd_ops = {
        /* Grow a .poll and .read_iter method at some point. */
+};
+
 #ifdef CONFIG_KALLSYMS
 /*
  * Provides a wchan file via kallsyms in a proper one-value-per-file format.
@@ -2987,6 +2990,7 @@ static const struct pid_entry tgid_base_stuff[] = {
        ONE("syscall",    S_IRUSR, proc_pid_syscall),
 #endif
        REG("cmdline",    S_IRUGO, proc_pid_cmdline_ops),
+       REG("pidfd",      S_IRUGO, proc_pid_pidfd_ops),
        ONE("stat",       S_IRUGO, proc_tgid_stat),
        ONE("statm",      S_IRUGO, proc_pid_statm),
        REG("maps",       S_IRUGO, proc_pid_maps_operations),
@@ -3076,8 +3080,7 @@ static const struct file_operations proc_tgid_base_operations = {

 struct pid *tgid_pidfd_to_pid(const struct file *file)
 {
-       if (!d_is_dir(file->f_path.dentry) ||
-           (file->f_op != &proc_tgid_base_operations))
+       if (file->f_op != &proc_pid_pidfd_ops)
                return ERR_PTR(-EBADF);

        return proc_pid(file_inode(file));