I run 2.6.35 linux kernel on Fedora 13. When I copy new files to a mounted CIFS share (either WinXP or Samba server), oplock is always disabled on these files.

Steps:
    1. sudo mount -t cifs //ip/share /mnt
    2. sudo cp new_files /mnt

Oplock status can be observed by adding the following code in cifs_file_aio_write():

        cFYI(1, "zn: cifs_file_aio_write(): clientCanCacheAll = %d",
             CIFS_I(inode)->clientCanCacheAll);
        cFYI(1, "zn: cifs_file_aio_write(): clientCanCacheRead = %d",
             CIFS_I(inode)->clientCanCacheRead);

In my test both clientCanCacheAll and clientCanCacheRead are set to 0 and filemap_fdatawrite() is always called.

I found that before cifs_create() calls cifs_new_fileinfo(), the value of "oplock" variable in cifs_create() is 0x20001 (CIFS_CREATE_ACTION | OPLOCK_EXCLUSIVE). But this value is not used in cifs_new_fileinfo(). Instead, a local "oplock" variable (set to REQ_OPLOCK) is used by cifs_new_fileinfo() to compare with OPLOCK_EXCLUSIVE/OPLOCK_READ. When the comparison fails, clientCanCacheAll/clientCanCacheRead are not set to "true".

cifs_new_fileinfo() is called by cifs_create(), cifs_open() and cifs_lookup(). Maybe it should accept oplock as a function parameter.

Sorry a patch is not provided because I'm new to Samba/CIFS code.

Regards,
zn