CIFS: Fix cache coherency for read oplock case

When we have a file opened with read oplock and we are writing a data
to this file, we need to store the data in the cache and then send to
the server to ensure that the next read operation will get a coherent
data.

Also mark it as CONFIG_CIFS_SMB2 because it's more suitable for SMB2
code but can fix some CIFS problems too (when server delays sending
an oplock break after a write request). We can drop this ifdefs
dependence in future.

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

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index ccad858d2d67f9fa2c3cc3bb80f1e3014a4eadc3..e93e3d2c69e68dc361040aedf26d71eba1fb2b56 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2461,11 +2461,30 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov,
                                                iocb->ki_filp->private_data;
        struct cifs_tcon *tcon = tlink_tcon(cfile->tlink);
 
+#ifdef CONFIG_CIFS_SMB2
        /*
-        * In strict cache mode we need to write the data to the server exactly
-        * from the pos to pos+len-1 rather than flush all affected pages
-        * because it may cause a error with mandatory locks on these pages but
-        * not on the region from pos to ppos+len-1.
+        * If we have an oplock for read and want to write a data to the file
+        * we need to store it in the page cache and then push it to the server
+        * to be sure the next read will get a valid data.
+        */
+       if (!cinode->clientCanCacheAll && cinode->clientCanCacheRead) {
+               ssize_t written;
+               int rc;
+
+               written = generic_file_aio_write(iocb, iov, nr_segs, pos);
+               rc = filemap_fdatawrite(inode->i_mapping);
+               if (rc)
+                       return (ssize_t)rc;
+
+               return written;
+       }
+#endif
+
+       /*
+        * For non-oplocked files in strict cache mode we need to write the data
+        * to the server exactly from the pos to pos+len-1 rather than flush all
+        * affected pages because it may cause a error with mandatory locks on
+        * these pages but not on the region from pos to ppos+len-1.
         */
 
        if (!cinode->clientCanCacheAll)