lockd: unlock lockd locks held for a certain filesystem

Add /proc/fs/nfsd/unlock_filesystem, which allows e.g.:

shell> echo /mnt/sfs1 > /proc/fs/nfsd/unlock_filesystem

so that a filesystem can be unmounted before allowing a peer nfsd to
take over nfs service for the 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, 32 insertions, 0 deletions

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 7706f6c9ab8a..42f3820ee8f5 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -56,6 +56,7 @@ enum {
         NFSD_List,
         NFSD_Fh,
         NFSD_FO_UnlockIP,
+        NFSD_FO_UnlockFS,
         NFSD_Threads,
         NFSD_Pool_Threads,
         NFSD_Versions,
@@ -93,6 +94,7 @@ 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 failover_unlock_fs(struct file *file, char *buf, size_t size);
 
 static ssize_t (*write_op[])(struct file *, char *, size_t) = {
         [NFSD_Svc] = write_svc,
@@ -104,6 +106,7 @@ static ssize_t (*write_op[])(struct file *, char *, size_t) = {
         [NFSD_Getfs] = write_getfs,
         [NFSD_Fh] = write_filehandle,
         [NFSD_FO_UnlockIP] = failover_unlock_ip,
+        [NFSD_FO_UnlockFS] = failover_unlock_fs,
         [NFSD_Threads] = write_threads,
         [NFSD_Pool_Threads] = write_pool_threads,
         [NFSD_Versions] = write_versions,
@@ -329,6 +332,33 @@ static ssize_t failover_unlock_ip(struct file *file, char *buf, size_t size)
         return nlmsvc_unlock_all_by_ip(server_ip);
 }
 
+static ssize_t failover_unlock_fs(struct file *file, char *buf, size_t size)
+{
+        struct nameidata nd;
+        char *fo_path;
+        int error;
+
+        /* 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;
+
+        error = path_lookup(fo_path, 0, &nd);
+        if (error)
+                return error;
+
+        error = nlmsvc_unlock_all_by_sb(nd.path.mnt->mnt_sb);
+
+        path_put(&nd.path);
+        return error;
+}
+
 static ssize_t write_filehandle(struct file *file, char *buf, size_t size)
 {
         /* request is:
@@ -733,6 +763,8 @@ static int nfsd_fill_super(struct super_block * sb, void * data, int silent)
                 [NFSD_List] = {"exports", &exports_operations, S_IRUGO},
                 [NFSD_FO_UnlockIP] = {"unlock_ip",
                                         &transaction_ops, S_IWUSR|S_IRUSR},
+                [NFSD_FO_UnlockFS] = {"unlock_filesystem",
+                                        &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},