linux/drivers/md/dm-hw-handler.h
Dave Wysochanski c9e45581ad dm mpath: add retry pg init
This patch allows a failed path group initialisation command to be retried.

It adds a generic MP_RETRY flag and a "pg_init_retries" feature to
device-mapper multipath which limits the number of retries.

1. A hw handler sends a path initialization command to the storage and
the command completes with an error code indicating the command
should be retried.

2. The hardware handler calls dm_pg_init_complete() with MP_RETRY
set in err_flags to ask the dm multipath core to retry.

3. If the retry limit has not been exceeded, pg_init() is retried.
Otherwise fail_path() is called.

If you are using the userspace multipath-tools or device-mapper-multipath
package, you can set pg_init_retries in the 'device' section of your
/etc/multipath.conf file. For example:

features                "2 pg_init_retries 7"

The number of PG retries attempted is reported in the 'dmsetup status' output.

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Acked-by: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2007-10-20 02:01:18 +01:00

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1.6 KiB
C

/*
* Copyright (C) 2004 Red Hat, Inc. All rights reserved.
*
* This file is released under the GPL.
*
* Multipath hardware handler registration.
*/
#ifndef DM_HW_HANDLER_H
#define DM_HW_HANDLER_H
#include <linux/device-mapper.h>
#include "dm-mpath.h"
struct hw_handler_type;
struct hw_handler {
struct hw_handler_type *type;
struct mapped_device *md;
void *context;
};
/*
* Constructs a hardware handler object, takes custom arguments
*/
/* Information about a hardware handler type */
struct hw_handler_type {
char *name;
struct module *module;
int (*create) (struct hw_handler *handler, unsigned int argc,
char **argv);
void (*destroy) (struct hw_handler *hwh);
void (*pg_init) (struct hw_handler *hwh, unsigned bypassed,
struct dm_path *path);
unsigned (*error) (struct hw_handler *hwh, struct bio *bio);
int (*status) (struct hw_handler *hwh, status_type_t type,
char *result, unsigned int maxlen);
};
/* Register a hardware handler */
int dm_register_hw_handler(struct hw_handler_type *type);
/* Unregister a hardware handler */
int dm_unregister_hw_handler(struct hw_handler_type *type);
/* Returns a registered hardware handler type */
struct hw_handler_type *dm_get_hw_handler(const char *name);
/* Releases a hardware handler */
void dm_put_hw_handler(struct hw_handler_type *hwht);
/* Default err function */
unsigned dm_scsi_err_handler(struct hw_handler *hwh, struct bio *bio);
/* Error flags for err and dm_pg_init_complete */
#define MP_FAIL_PATH 1
#define MP_BYPASS_PG 2
#define MP_ERROR_IO 4 /* Don't retry this I/O */
#define MP_RETRY 8
#endif