1 files changed, 16 insertions, 3 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 39672b731736..c3f2477c16c1 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -758,6 +758,11 @@ do_unlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 }
 
 static int
+is_time_granular(struct timespec *ts) {
+        return ((ts->tv_sec == 0) && (ts->tv_nsec <= 1000));
+}
+
+static int
 do_setlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
 {
         struct inode *inode = filp->f_mapping->host;
@@ -781,13 +786,21 @@ do_setlk(struct file *filp, int cmd, struct file_lock *fl, int is_local)
                 status = do_vfs_lock(filp, fl);
         if (status < 0)
                 goto out;
+
         /*
-         * Make sure we clear the cache whenever we try to get the lock.
+         * Revalidate the cache if the server has time stamps granular
+         * enough to detect subsecond changes.  Otherwise, clear the
+         * cache to prevent missing any changes.
+         *
          * This makes locking act as a cache coherency point.
          */
         nfs_sync_mapping(filp->f_mapping);
-        if (!nfs_have_delegation(inode, FMODE_READ))
-                nfs_zap_caches(inode);
+        if (!nfs_have_delegation(inode, FMODE_READ)) {
+                if (is_time_granular(&NFS_SERVER(inode)->time_delta))
+                        __nfs_revalidate_inode(NFS_SERVER(inode), inode);
+                else
+                        nfs_zap_caches(inode);
+        }
 out:
         return status;
 }