md/r5cache: disable write back for degraded array

write-back cache in degraded mode introduces corner cases to the array.
Although we try to cover all these corner cases, it is safer to just
disable write-back cache when the array is in degraded mode.

In this patch, we disable writeback cache for degraded mode:
1. On device failure, if the array enters degraded mode, raid5_error()
   will submit async job r5c_disable_writeback_async to disable
   writeback;
2. In r5c_journal_mode_store(), it is invalid to enable writeback in
   degraded mode;
3. In r5c_try_caching_write(), stripes with s->failed>0 will be handled
   in write-through mode.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>

path: root/sound/pci/ctxfi/cthw20k2.h

/**
 * Copyright (C) 2008, Creative Technology Ltd. All Rights Reserved.
 *
 * This source file is released under GPL v2 license (no other versions).
 * See the COPYING file included in the main directory of this source
 * distribution for the license terms and conditions.
 *
 * @File	cthw20k2.h
 *
 * @Brief
 * This file contains the definition of hardware access methord.
 *
 * @Author	Liu Chun
 * @Date 	May 13 2008
 *
 */

#ifndef CTHW20K2_H
#define CTHW20K2_H

#include "cthardware.h"

int create_20k2_hw_obj(struct hw **rhw);
int destroy_20k2_hw_obj(struct hw *hw);

#endif /* CTHW20K2_H */