CIFS: Add rwpidforward mount option

Add rwpidforward mount option that switches on a mode when we forward
pid of a process who opened a file to any read and write operation.

This can prevent applications like WINE from failing on read or write
operation on a previously locked file region from the same netfd from
another process if we use mandatory brlock style.

It is actual for WINE because during a run of WINE program two processes
work on the same netfd - share the same file struct between several VFS
fds:
1) WINE-server does open and lock;
2) WINE-application does read and write.

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/cifs/README b/fs/cifs/README
index 4a3ca0e5ca24..c5c2c5e5f0f2 100644
--- a/fs/cifs/README
+++ b/fs/cifs/README
@@ -457,6 +457,9 @@ A partial list of the supported mount options follows:
                 otherwise - read from the server. All written data are stored
                 in the cache, but if the client doesn't have Exclusive Oplock,
                 it writes the data to the server.
+  rwpidforward  Forward pid of a process who opened a file to any read or write
+                operation on that file. This prevent applications like WINE
+                from failing on read and write if we use mandatory brlock style.
   acl           Allow setfacl and getfacl to manage posix ACLs if server
                 supports them.  (default)
   noacl         Do not allow setfacl and getfacl calls on this mount