lockd: unlock lockd locks associated with a given server ip

For high-availability NFS service, we generally need to be able to drop
file locks held on the exported filesystem before moving clients to a
new server.  Currently the only way to do that is by shutting down lockd
entirely, which is often undesireable (for example, if you want to
continue exporting other filesystems).

This patch allows the administrator to release all locks held by clients
accessing the client through a given server ip address, by echoing that
address to a new file, /proc/fs/nfsd/unlock_ip, as in:

shell> echo 10.1.1.2 > /proc/fs/nfsd/unlock_ip

The expected sequence of events can be:
1. Tear down the IP address
2. Unexport the path
3. Write IP to /proc/fs/nfsd/unlock_ip to unlock files
4. Signal peer to begin take-over.

For now we only support IPv4 addresses and NFSv2/v3 (NFSv4 locks are not
affected).

Also, if unmounting the filesystem is required, we assume at step 3 that
clients using the given server ip are the only clients holding locks on
the given filesystem; otherwise, an additional patch is required to
allow revoking all locks held by lockd on a given filesystem.

Signed-off-by: S. Wendy Cheng <wcheng@redhat.com>
Cc: Lon Hohberger  <lhh@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

 fs/lockd/svcsubs.c          |   66 +++++++++++++++++++++++++++++++++++++++-----
 fs/nfsd/nfsctl.c            |   65 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/lockd/lockd.h |    7 ++++
 3 files changed, 131 insertions(+), 7 deletions(-)

1 files changed, 33 insertions, 0 deletions

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 613bcb8171a5..7706f6c9ab8a 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -22,6 +22,7 @@
 #include <linux/seq_file.h>
 #include <linux/pagemap.h>
 #include <linux/init.h>
+#include <linux/inet.h>
 #include <linux/string.h>
 #include <linux/smp_lock.h>
 #include <linux/ctype.h>
@@ -35,6 +36,7 @@
 #include <linux/nfsd/cache.h>
 #include <linux/nfsd/xdr.h>
 #include <linux/nfsd/syscall.h>
+#include <linux/lockd/lockd.h>
 
 #include <asm/uaccess.h>
 #include <net/ipv6.h>
@@ -53,6 +55,7 @@ enum {
 	NFSD_Getfs,
 	NFSD_List,
 	NFSD_Fh,
+	NFSD_FO_UnlockIP,
 	NFSD_Threads,
 	NFSD_Pool_Threads,
 	NFSD_Versions,
@@ -89,6 +92,8 @@ static ssize_t write_leasetime(struct file *file, char *buf, size_t size);
 static ssize_t write_recoverydir(struct file *file, char *buf, size_t size);
 #endif
 
+static ssize_t failover_unlock_ip(struct file *file, char *buf, size_t size);
+
 static ssize_t (*write_op[])(struct file *, char *, size_t) = {
 	[NFSD_Svc] = write_svc,
 	[NFSD_Add] = write_add,
@@ -98,6 +103,7 @@ static ssize_t (*write_op[])(struct file *, char *, size_t) = {
 	[NFSD_Getfd] = write_getfd,
 	[NFSD_Getfs] = write_getfs,
 	[NFSD_Fh] = write_filehandle,
+	[NFSD_FO_UnlockIP] = failover_unlock_ip,
 	[NFSD_Threads] = write_threads,
 	[NFSD_Pool_Threads] = write_pool_threads,
 	[NFSD_Versions] = write_versions,
@@ -298,6 +304,31 @@ static ssize_t write_getfd(struct file *file, char *buf, size_t size)
 	return err;
 }
 
+static ssize_t failover_unlock_ip(struct file *file, char *buf, size_t size)
+{
+	__be32 server_ip;
+	char *fo_path, c;
+	int b1, b2, b3, b4;
+
+	/* sanity check */
+	if (size == 0)
+		return -EINVAL;
+
+	if (buf[size-1] != '\n')
+		return -EINVAL;
+
+	fo_path = buf;
+	if (qword_get(&buf, fo_path, size) < 0)
+		return -EINVAL;
+
+	/* get ipv4 address */
+	if (sscanf(fo_path, "%u.%u.%u.%u%c", &b1, &b2, &b3, &b4, &c) != 4)
+		return -EINVAL;
+	server_ip = htonl((((((b1<<8)|b2)<<8)|b3)<<8)|b4);
+
+	return nlmsvc_unlock_all_by_ip(server_ip);
+}
+
 static ssize_t write_filehandle(struct file *file, char *buf, size_t size)
 {
 	/* request is:
@@ -700,6 +731,8 @@ static int nfsd_fill_super(struct super_block * sb, void * data, int silent)
 		[NFSD_Getfd] = {".getfd", &transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_Getfs] = {".getfs", &transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_List] = {"exports", &exports_operations, S_IRUGO},
+		[NFSD_FO_UnlockIP] = {"unlock_ip",
+					&transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_Fh] = {"filehandle", &transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_Threads] = {"threads", &transaction_ops, S_IWUSR|S_IRUSR},
 		[NFSD_Pool_Threads] = {"pool_threads", &transaction_ops, S_IWUSR|S_IRUSR},