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, 8 insertions, 3 deletions

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 53ea6250a51d..e2d9dd817ba0 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -374,6 +374,7 @@ cifs_sfu_type(struct cifs_fattr *fattr, const unsigned char *path,
         __u16 netfid;
         struct tcon_link *tlink;
         struct cifsTconInfo *tcon;
+        struct cifs_io_parms io_parms;
         char buf[24];
         unsigned int bytes_read;
         char *pbuf;
@@ -405,9 +406,13 @@ cifs_sfu_type(struct cifs_fattr *fattr, const unsigned char *path,
         if (rc == 0) {
                 int buf_type = CIFS_NO_BUFFER;
                         /* Read header */
-                rc = CIFSSMBRead(xid, tcon, netfid,
-                                 24 /* length */, 0 /* offset */,
-                                 &bytes_read, &pbuf, &buf_type);
+                io_parms.netfid = netfid;
+                io_parms.pid = current->tgid;
+                io_parms.tcon = tcon;
+                io_parms.offset = 0;
+                io_parms.length = 24;
+                rc = CIFSSMBRead(xid, &io_parms, &bytes_read, &pbuf,
+                                 &buf_type);
                 if ((rc == 0) && (bytes_read >= 8)) {
                         if (memcmp("IntxBLK", pbuf, 8) == 0) {
                                 cFYI(1, "Block device");