CIFS: Fix write after setting a read lock for read oplock files

If we have a read oplock and set a read lock in it, we can't write to the
locked area - so, filemap_fdatawrite may fail with a no information for a
userspace application even if we request a write to non-locked area. Fix
this by writing directly to the server and then breaking oplock level from
level2 to None.

Also remove CONFIG_CIFS_SMB2 ifdefs because it's suitable for both CIFS
and SMB2 protocols.

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/file.c

@@ -2505,42 +2505,34 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov,
 	struct cifsFileInfo *cfile = (struct cifsFileInfo *)
 						iocb->ki_filp->private_data;
 	struct cifs_tcon *tcon = tlink_tcon(cfile->tlink);
+	ssize_t written;
 
-#ifdef CONFIG_CIFS_SMB2
-	/*
-	 * 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;
+	if (cinode->clientCanCacheAll) {
+		if (cap_unix(tcon->ses) &&
+		(CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability))
+		    && ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0))
+			return generic_file_aio_write(iocb, iov, nr_segs, pos);
+		return cifs_writev(iocb, iov, nr_segs, pos);
 	}
-#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)
-		return cifs_user_writev(iocb, iov, nr_segs, pos);
-
-	if (cap_unix(tcon->ses) &&
-	    (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability)) &&
-	    ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0))
-		return generic_file_aio_write(iocb, iov, nr_segs, pos);
-
-	return cifs_writev(iocb, iov, nr_segs, pos);
+	written = cifs_user_writev(iocb, iov, nr_segs, pos);
+	if (written > 0 && cinode->clientCanCacheRead) {
+		/*
+		 * Windows 7 server can delay breaking level2 oplock if a write
+		 * request comes - break it on the client to prevent reading
+		 * an old data.
+		 */
+		cifs_invalidate_mapping(inode);
+		cFYI(1, "Set no oplock for inode=%p after a write operation",
+		     inode);
+		cinode->clientCanCacheRead = false;
+	}
+	return written;
 }
 
 static struct cifs_readdata *