lockd: add a /proc/fs/lockd/nlm_end_grace file

Add a new procfile that will allow a (privileged) userland process to
end the NLM grace period early. The basic idea here will be to have
sm-notify write to this file, if it sent out no NOTIFY requests when
it runs. In that situation, we can generally expect that there will be
no reclaim requests so the grace period can be lifted early.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>

4 files changed, 130 insertions, 0 deletions

diff --git a/fs/lockd/Makefile b/fs/lockd/Makefile
index 6a0b351ce30e..9b320cc2a8cf 100644
--- a/fs/lockd/Makefile
+++ b/fs/lockd/Makefile
@@ -7,4 +7,5 @@ obj-$(CONFIG_LOCKD) += lockd.o
 lockd-objs-y := clntlock.o clntproc.o clntxdr.o host.o svc.o svclock.o \
                 svcshare.o svcproc.o svcsubs.o mon.o xdr.o
 lockd-objs-$(CONFIG_LOCKD_V4) += clnt4xdr.o xdr4.o svc4proc.o
+lockd-objs-$(CONFIG_PROC_FS) += procfs.o
 lockd-objs                    := $(lockd-objs-y)
diff --git a/fs/lockd/procfs.c b/fs/lockd/procfs.c
new file mode 100644
index 000000000000..2a0a98480e39
--- /dev/null
+++ b/fs/lockd/procfs.c
@@ -0,0 +1,92 @@
+/*
+ * Procfs support for lockd
+ *
+ * Copyright (c) 2014 Jeff Layton <jlayton@primarydata.com>
+ */
+
+#include <linux/fs.h>
+#include <linux/proc_fs.h>
+#include <linux/module.h>
+#include <linux/nsproxy.h>
+#include <net/net_namespace.h>
+
+#include "netns.h"
+#include "procfs.h"
+
+/*
+ * We only allow strings that start with 'Y', 'y', or '1'.
+ */
+static ssize_t
+nlm_end_grace_write(struct file *file, const char __user *buf, size_t size,
+                    loff_t *pos)
+{
+        char *data;
+        struct lockd_net *ln = net_generic(current->nsproxy->net_ns,
+                                           lockd_net_id);
+
+        if (size < 1)
+                return -EINVAL;
+
+        data = simple_transaction_get(file, buf, size);
+        if (IS_ERR(data))
+                return PTR_ERR(data);
+
+        switch(data[0]) {
+        case 'Y':
+        case 'y':
+        case '1':
+                locks_end_grace(&ln->lockd_manager);
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        return size;
+}
+
+static ssize_t
+nlm_end_grace_read(struct file *file, char __user *buf, size_t size,
+                   loff_t *pos)
+{
+        struct lockd_net *ln = net_generic(current->nsproxy->net_ns,
+                                           lockd_net_id);
+        char resp[3];
+
+        resp[0] = list_empty(&ln->lockd_manager.list) ? 'Y' : 'N';
+        resp[1] = '\n';
+        resp[2] = '\0';
+
+        return simple_read_from_buffer(buf, size, pos, resp, sizeof(resp));
+}
+
+static const struct file_operations lockd_end_grace_operations = {
+        .write          = nlm_end_grace_write,
+        .read           = nlm_end_grace_read,
+        .llseek         = default_llseek,
+        .release        = simple_transaction_release,
+        .owner          = THIS_MODULE,
+};
+
+int __init
+lockd_create_procfs(void)
+{
+        struct proc_dir_entry *entry;
+
+        entry = proc_mkdir("fs/lockd", NULL);
+        if (!entry)
+                return -ENOMEM;
+        entry = proc_create("nlm_end_grace", S_IRUGO|S_IWUSR, entry,
+                                 &lockd_end_grace_operations);
+        if (!entry) {
+                remove_proc_entry("fs/lockd", NULL);
+                return -ENOMEM;
+        }
+        return 0;
+}
+
+void __exit
+lockd_remove_procfs(void)
+{
+        remove_proc_entry("fs/lockd/nlm_end_grace", NULL);
+        remove_proc_entry("fs/lockd", NULL);
+}
diff --git a/fs/lockd/procfs.h b/fs/lockd/procfs.h
new file mode 100644
index 000000000000..2257a1311027
--- /dev/null
+++ b/fs/lockd/procfs.h
@@ -0,0 +1,28 @@
+/*
+ * Procfs support for lockd
+ *
+ * Copyright (c) 2014 Jeff Layton <jlayton@primarydata.com>
+ */
+#ifndef _LOCKD_PROCFS_H
+#define _LOCKD_PROCFS_H
+
+#include <linux/kconfig.h>
+
+#if IS_ENABLED(CONFIG_PROC_FS)
+int lockd_create_procfs(void);
+void lockd_remove_procfs(void);
+#else
+static inline int
+lockd_create_procfs(void)
+{
+        return 0;
+}
+
+static inline void
+lockd_remove_procfs(void)
+{
+        return;
+}
+#endif /* IS_ENABLED(CONFIG_PROC_FS) */
+
+#endif /* _LOCKD_PROCFS_H */
diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index 266b67972305..8146cfe97d8d 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -36,6 +36,7 @@
 #include <linux/nfs.h>
 
 #include "netns.h"
+#include "procfs.h"
 
 #define NLMDBG_FACILITY         NLMDBG_SVC
 #define LOCKD_BUFSIZE           (1024 + NLMSVC_XDRSIZE)
@@ -620,8 +621,15 @@ static int __init init_nlm(void)
         err = register_pernet_subsys(&lockd_net_ops);
         if (err)
                 goto err_pernet;
+
+        err = lockd_create_procfs();
+        if (err)
+                goto err_procfs;
+
         return 0;
 
+err_procfs:
+        unregister_pernet_subsys(&lockd_net_ops);
 err_pernet:
 #ifdef CONFIG_SYSCTL
         unregister_sysctl_table(nlm_sysctl_table);
@@ -634,6 +642,7 @@ static void __exit exit_nlm(void)
 {
         /* FIXME: delete all NLM clients */
         nlm_shutdown_hosts();
+        lockd_remove_procfs();
         unregister_pernet_subsys(&lockd_net_ops);
 #ifdef CONFIG_SYSCTL
         unregister_sysctl_table(nlm_sysctl_table);