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, 14 insertions, 8 deletions

diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index 1a6a388cf5d8..4682d44b6f5b 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -235,6 +235,7 @@ CIFSQueryMFSymLink(const int xid, struct cifsTconInfo *tcon,
         unsigned int bytes_read = 0;
         int buf_type = CIFS_NO_BUFFER;
         unsigned int link_len = 0;
+        struct cifs_io_parms io_parms;
         FILE_ALL_INFO file_info;
 
         rc = CIFSSMBOpen(xid, tcon, searchName, FILE_OPEN, GENERIC_READ,
@@ -253,11 +254,13 @@ CIFSQueryMFSymLink(const int xid, struct cifsTconInfo *tcon,
         if (!buf)
                 return -ENOMEM;
         pbuf = buf;
+        io_parms.netfid = netfid;
+        io_parms.pid = current->tgid;
+        io_parms.tcon = tcon;
+        io_parms.offset = 0;
+        io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;
 
-        rc = CIFSSMBRead(xid, tcon, netfid,
-                         CIFS_MF_SYMLINK_FILE_SIZE /* length */,
-                         0 /* offset */,
-                         &bytes_read, &pbuf, &buf_type);
+        rc = CIFSSMBRead(xid, &io_parms, &bytes_read, &pbuf, &buf_type);
         CIFSSMBClose(xid, tcon, netfid);
         if (rc != 0) {
                 kfree(buf);
@@ -296,6 +299,7 @@ CIFSCheckMFSymlink(struct cifs_fattr *fattr,
         __u16 netfid = 0;
         struct tcon_link *tlink;
         struct cifsTconInfo *pTcon;
+        struct cifs_io_parms io_parms;
         u8 *buf;
         char *pbuf;
         unsigned int bytes_read = 0;
@@ -332,11 +336,13 @@ CIFSCheckMFSymlink(struct cifs_fattr *fattr,
                 goto out;
         }
         pbuf = buf;
+        io_parms.netfid = netfid;
+        io_parms.pid = current->tgid;
+        io_parms.tcon = pTcon;
+        io_parms.offset = 0;
+        io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;
 
-        rc = CIFSSMBRead(xid, pTcon, netfid,
-                         CIFS_MF_SYMLINK_FILE_SIZE /* length */,
-                         0 /* offset */,
-                         &bytes_read, &pbuf, &buf_type);
+        rc = CIFSSMBRead(xid, &io_parms, &bytes_read, &pbuf, &buf_type);
         CIFSSMBClose(xid, pTcon, netfid);
         if (rc != 0) {
                 kfree(buf);