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linux-next/drivers/scsi/scsi_priv.h
Christoph Hellwig d285203cf6 scsi: add support for a blk-mq based I/O path. 
This patch adds support for an alternate I/O path in the scsi midlayer
which uses the blk-mq infrastructure instead of the legacy request code.

Use of blk-mq is fully transparent to drivers, although for now a host
template field is provided to opt out of blk-mq usage in case any unforseen
incompatibilities arise.

In general replacing the legacy request code with blk-mq is a simple and
mostly mechanical transformation.  The biggest exception is the new code
that deals with the fact the I/O submissions in blk-mq must happen from
process context, which slightly complicates the I/O completion handler.
The second biggest differences is that blk-mq is build around the concept
of preallocated requests that also include driver specific data, which
in SCSI context means the scsi_cmnd structure.  This completely avoids
dynamic memory allocations for the fast path through I/O submission.

Due the preallocated requests the MQ code path exclusively uses the
host-wide shared tag allocator instead of a per-LUN one.  This only
affects drivers actually using the block layer provided tag allocator
instead of their own.  Unlike the old path blk-mq always provides a tag,
although drivers don't have to use it.

For now the blk-mq path is disable by defauly and must be enabled using
the "use_blk_mq" module parameter.  Once the remaining work in the block
layer to make blk-mq more suitable for slow devices is complete I hope
to make it the default and eventually even remove the old code path.

Based on the earlier scsi-mq prototype by Nicholas Bellinger.

Thanks to Bart Van Assche and Robert Elliot for testing, benchmarking and
various sugestions and code contributions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Webb Scales <webbnh@hp.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Tested-by: Bart Van Assche <bvanassche@acm.org>
Tested-by: Robert Elliott <elliott@hp.com>
2014-07-25 17:16:28 -04:00

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#ifndef _SCSI_PRIV_H
#define _SCSI_PRIV_H
#include <linux/device.h>
#include <linux/async.h>
#include <scsi/scsi_device.h>
struct request_queue;
struct request;
struct scsi_cmnd;
struct scsi_device;
struct scsi_target;
struct scsi_host_template;
struct Scsi_Host;
struct scsi_nl_hdr;
/*
* Scsi Error Handler Flags
*/
#define SCSI_EH_CANCEL_CMD 0x0001 /* Cancel this cmd */
#define SCSI_EH_ABORT_SCHEDULED 0x0002 /* Abort has been scheduled */
#define SCSI_SENSE_VALID(scmd) \
(((scmd)->sense_buffer[0] & 0x70) == 0x70)
/* hosts.c */
extern int scsi_init_hosts(void);
extern void scsi_exit_hosts(void);
/* scsi.c */
extern int scsi_dispatch_cmd(struct scsi_cmnd *cmd);
extern int scsi_setup_command_freelist(struct Scsi_Host *shost);
extern void scsi_destroy_command_freelist(struct Scsi_Host *shost);
#ifdef CONFIG_SCSI_LOGGING
void scsi_log_send(struct scsi_cmnd *cmd);
void scsi_log_completion(struct scsi_cmnd *cmd, int disposition);
#else
static inline void scsi_log_send(struct scsi_cmnd *cmd)
{ };
static inline void scsi_log_completion(struct scsi_cmnd *cmd, int disposition)
{ };
#endif
/* scsi_devinfo.c */
/* list of keys for the lists */
enum {
SCSI_DEVINFO_GLOBAL = 0,
SCSI_DEVINFO_SPI,
};
extern int scsi_get_device_flags(struct scsi_device *sdev,
const unsigned char *vendor,
const unsigned char *model);
extern int scsi_get_device_flags_keyed(struct scsi_device *sdev,
const unsigned char *vendor,
const unsigned char *model, int key);
extern int scsi_dev_info_list_add_keyed(int compatible, char *vendor,
char *model, char *strflags,
int flags, int key);
extern int scsi_dev_info_list_del_keyed(char *vendor, char *model, int key);
extern int scsi_dev_info_add_list(int key, const char *name);
extern int scsi_dev_info_remove_list(int key);
extern int __init scsi_init_devinfo(void);
extern void scsi_exit_devinfo(void);
/* scsi_error.c */
extern void scmd_eh_abort_handler(struct work_struct *work);
extern enum blk_eh_timer_return scsi_times_out(struct request *req);
extern int scsi_error_handler(void *host);
extern int scsi_decide_disposition(struct scsi_cmnd *cmd);
extern void scsi_eh_wakeup(struct Scsi_Host *shost);
extern int scsi_eh_scmd_add(struct scsi_cmnd *, int);
void scsi_eh_ready_devs(struct Scsi_Host *shost,
struct list_head *work_q,
struct list_head *done_q);
int scsi_eh_get_sense(struct list_head *work_q,
struct list_head *done_q);
int scsi_noretry_cmd(struct scsi_cmnd *scmd);
/* scsi_lib.c */
extern int scsi_maybe_unblock_host(struct scsi_device *sdev);
extern void scsi_device_unbusy(struct scsi_device *sdev);
extern void scsi_queue_insert(struct scsi_cmnd *cmd, int reason);
extern void scsi_next_command(struct scsi_cmnd *cmd);
extern void scsi_io_completion(struct scsi_cmnd *, unsigned int);
extern void scsi_run_host_queues(struct Scsi_Host *shost);
extern struct request_queue *scsi_alloc_queue(struct scsi_device *sdev);
extern struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev);
extern int scsi_mq_setup_tags(struct Scsi_Host *shost);
extern void scsi_mq_destroy_tags(struct Scsi_Host *shost);
extern int scsi_init_queue(void);
extern void scsi_exit_queue(void);
struct request_queue;
struct request;
extern struct kmem_cache *scsi_sdb_cache;
/* scsi_proc.c */
#ifdef CONFIG_SCSI_PROC_FS
extern void scsi_proc_hostdir_add(struct scsi_host_template *);
extern void scsi_proc_hostdir_rm(struct scsi_host_template *);
extern void scsi_proc_host_add(struct Scsi_Host *);
extern void scsi_proc_host_rm(struct Scsi_Host *);
extern int scsi_init_procfs(void);
extern void scsi_exit_procfs(void);
#else
# define scsi_proc_hostdir_add(sht) do { } while (0)
# define scsi_proc_hostdir_rm(sht) do { } while (0)
# define scsi_proc_host_add(shost) do { } while (0)
# define scsi_proc_host_rm(shost) do { } while (0)
# define scsi_init_procfs() (0)
# define scsi_exit_procfs() do { } while (0)
#endif /* CONFIG_PROC_FS */
/* scsi_scan.c */
extern char scsi_scan_type[];
extern int scsi_complete_async_scans(void);
extern int scsi_scan_host_selected(struct Scsi_Host *, unsigned int,
unsigned int, u64, int);
extern void scsi_forget_host(struct Scsi_Host *);
extern void scsi_rescan_device(struct device *);
/* scsi_sysctl.c */
#ifdef CONFIG_SYSCTL
extern int scsi_init_sysctl(void);
extern void scsi_exit_sysctl(void);
#else
# define scsi_init_sysctl() (0)
# define scsi_exit_sysctl() do { } while (0)
#endif /* CONFIG_SYSCTL */
/* scsi_sysfs.c */
extern int scsi_sysfs_add_sdev(struct scsi_device *);
extern int scsi_sysfs_add_host(struct Scsi_Host *);
extern int scsi_sysfs_register(void);
extern void scsi_sysfs_unregister(void);
extern void scsi_sysfs_device_initialize(struct scsi_device *);
extern int scsi_sysfs_target_initialize(struct scsi_device *);
extern struct scsi_transport_template blank_transport_template;
extern void __scsi_remove_device(struct scsi_device *);
extern struct bus_type scsi_bus_type;
extern const struct attribute_group *scsi_sysfs_shost_attr_groups[];
/* scsi_netlink.c */
#ifdef CONFIG_SCSI_NETLINK
extern void scsi_netlink_init(void);
extern void scsi_netlink_exit(void);
extern struct sock *scsi_nl_sock;
#else
static inline void scsi_netlink_init(void) {}
static inline void scsi_netlink_exit(void) {}
#endif
/* scsi_pm.c */
#ifdef CONFIG_PM
extern const struct dev_pm_ops scsi_bus_pm_ops;
#endif
#ifdef CONFIG_PM_RUNTIME
extern void scsi_autopm_get_target(struct scsi_target *);
extern void scsi_autopm_put_target(struct scsi_target *);
extern int scsi_autopm_get_host(struct Scsi_Host *);
extern void scsi_autopm_put_host(struct Scsi_Host *);
#else
static inline void scsi_autopm_get_target(struct scsi_target *t) {}
static inline void scsi_autopm_put_target(struct scsi_target *t) {}
static inline int scsi_autopm_get_host(struct Scsi_Host *h) { return 0; }
static inline void scsi_autopm_put_host(struct Scsi_Host *h) {}
#endif /* CONFIG_PM_RUNTIME */
extern struct async_domain scsi_sd_pm_domain;
extern struct async_domain scsi_sd_probe_domain;
/*
* internal scsi timeout functions: for use by mid-layer and transport
* classes.
*/
#define SCSI_DEVICE_BLOCK_MAX_TIMEOUT 600 /* units in seconds */
extern int scsi_internal_device_block(struct scsi_device *sdev);
extern int scsi_internal_device_unblock(struct scsi_device *sdev,
enum scsi_device_state new_state);
#endif /* _SCSI_PRIV_H */
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