nfsd: add a v4_end_grace file to /proc/fs/nfsd

Allow a privileged userland process to end the v4 grace period early.
Writing "Y", "y", or "1" to the file will cause the v4 grace period to
be lifted.  The basic idea with this will be to allow the userland
client tracking program to lift the grace period once it knows that no
more clients will be reclaiming state.

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

1 files changed, 45 insertions, 0 deletions

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 4e042105fb6e..ca73ca79a0ee 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -49,6 +49,7 @@ enum {
         NFSD_Leasetime,
         NFSD_Gracetime,
         NFSD_RecoveryDir,
+        NFSD_V4EndGrace,
 #endif
 };
 
@@ -68,6 +69,7 @@ static ssize_t write_maxconn(struct file *file, char *buf, size_t size);
 static ssize_t write_leasetime(struct file *file, char *buf, size_t size);
 static ssize_t write_gracetime(struct file *file, char *buf, size_t size);
 static ssize_t write_recoverydir(struct file *file, char *buf, size_t size);
+static ssize_t write_v4_end_grace(struct file *file, char *buf, size_t size);
 #endif
 
 static ssize_t (*write_op[])(struct file *, char *, size_t) = {
@@ -84,6 +86,7 @@ static ssize_t (*write_op[])(struct file *, char *, size_t) = {
         [NFSD_Leasetime] = write_leasetime,
         [NFSD_Gracetime] = write_gracetime,
         [NFSD_RecoveryDir] = write_recoverydir,
+        [NFSD_V4EndGrace] = write_v4_end_grace,
 #endif
 };
 
@@ -1077,6 +1080,47 @@ static ssize_t write_recoverydir(struct file *file, char *buf, size_t size)
         return rv;
 }
 
+/**
+ * write_v4_end_grace - release grace period for nfsd's v4.x lock manager
+ *
+ * Input:
+ *                      buf:            ignored
+ *                      size:           zero
+ * OR
+ *
+ * Input:
+ *                      buf:            any value
+ *                      size:           non-zero length of C string in @buf
+ * Output:
+ *                      passed-in buffer filled with "Y" or "N" with a newline
+ *                      and NULL-terminated C string. This indicates whether
+ *                      the grace period has ended in the current net
+ *                      namespace. Return code is the size in bytes of the
+ *                      string. Writing a string that starts with 'Y', 'y', or
+ *                      '1' to the file will end the grace period for nfsd's v4
+ *                      lock manager.
+ */
+static ssize_t write_v4_end_grace(struct file *file, char *buf, size_t size)
+{
+        struct net *net = file->f_dentry->d_sb->s_fs_info;
+        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
+        if (size > 0) {
+                switch(buf[0]) {
+                case 'Y':
+                case 'y':
+                case '1':
+                        nfsd4_end_grace(nn);
+                        break;
+                default:
+                        return -EINVAL;
+                }
+        }
+
+        return scnprintf(buf, SIMPLE_TRANSACTION_LIMIT, "%c\n",
+                         nn->grace_ended ? 'Y' : 'N');
+}
+
 #endif
 
 /*----------------------------------------------------------------------------*/
@@ -1110,6 +1154,7 @@ static int nfsd_fill_super(struct super_block * sb, void * data, int silent)
                 [NFSD_Leasetime] = {"nfsv4leasetime", &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_Gracetime] = {"nfsv4gracetime", &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_RecoveryDir] = {"nfsv4recoverydir", &transaction_ops, S_IWUSR|S_IRUSR},
+                [NFSD_V4EndGrace] = {"v4_end_grace", &transaction_ops, S_IWUSR|S_IRUGO},
 #endif
                 /* last one */ {""}
         };