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[SCSI] remove scsi_request infrastructure

Browse Source 
With Achim patch the last user (gdth) is switched away from scsi_request
so we an kill it now.  Also disables some code in i2o_scsi that was
broken since the sg driver stopped using scsi_requests.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
This commit is contained in:
Christoph Hellwig 2006-06-10 18:01:03 +02:00 committed by James Bottomley
parent 1951d099df
commit beb4048750
19 changed files with 14 additions and 370 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/message/i2o/i2o_scsi.c
View File

@ -65,9 +65,7 @@
#include <scsi/scsi_host.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_request.h>
#include <scsi/sg.h>
#include <scsi/sg_request.h>
#define OSM_NAME "scsi-osm"
#define OSM_VERSION "1.316"
@ -588,6 +586,7 @@ static int i2o_scsi_queuecommand(struct scsi_cmnd *SCpnt,
mptr = &msg->body[0];
#if 0 /* this code can't work */
#ifdef CONFIG_I2O_EXT_ADAPTEC
if (c->adaptec) {
u32 adpt_flags = 0;
@ -624,6 +623,7 @@ static int i2o_scsi_queuecommand(struct scsi_cmnd *SCpnt,
*mptr++ = cpu_to_le32(I2O_VENDOR_DPT << 16 | I2O_CMD_SCSI_EXEC);
*mptr++ = cpu_to_le32(adpt_flags | tid);
}
#endif
#endif
msg->u.head[1] = cpu_to_le32(cmd | HOST_TID << 12 | tid);

12
drivers/scsi/constants.c
View File

@ -13,9 +13,9 @@
#include <linux/kernel.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_request.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_dbg.h>
@ -1261,16 +1261,6 @@ void scsi_print_sense(const char *devclass, struct scsi_cmnd *cmd)
}
EXPORT_SYMBOL(scsi_print_sense);
void scsi_print_req_sense(const char *devclass, struct scsi_request *sreq)
{
const char *name = devclass;
if (sreq->sr_request->rq_disk)
name = sreq->sr_request->rq_disk->disk_name;
__scsi_print_sense(name, sreq->sr_sense_buffer, SCSI_SENSE_BUFFERSIZE);
}
EXPORT_SYMBOL(scsi_print_req_sense);
void scsi_print_command(struct scsi_cmnd *cmd)
{
/* Assume appended output (i.e. not at start of line) */

8
drivers/scsi/gdth.c
View File

@ -716,8 +716,8 @@ static void gdth_scsi_done(struct scsi_cmnd *scp)
{
TRACE2(("gdth_scsi_done()\n"));
if (scp->sc_request)
complete((struct completion *)scp->sc_request);
if (scp->request)
complete((struct completion *)scp->request);
}
int __gdth_execute(struct scsi_device *sdev, gdth_cmd_str *gdtcmd, char *cmnd,
@ -732,8 +732,8 @@ int __gdth_execute(struct scsi_device *sdev, gdth_cmd_str *gdtcmd, char *cmnd,
return -ENOMEM;
memset(scp, 0, sizeof(*scp));
scp->device = sdev;
/* use sc_request field to save the ptr. to completion struct. */
scp->sc_request = (struct scsi_request *)&wait;
/* use request field to save the ptr. to completion struct. */
scp->request = (struct request *)&wait;
scp->timeout_per_command = timeout*HZ;
scp->request_buffer = gdtcmd;
scp->cmd_len = 12;

1
drivers/scsi/ipr.c
View File

@ -79,7 +79,6 @@
#include <scsi/scsi_tcq.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_request.h>
#include "ipr.h"
/*

2
drivers/scsi/libata-scsi.c
View File

@ -38,9 +38,9 @@
#include <linux/spinlock.h>
#include <scsi/scsi.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_request.h>
#include <scsi/scsi_transport.h>
#include <linux/libata.h>
#include <linux/hdreg.h>

1
drivers/scsi/qlogicpti.c
View File

@ -43,7 +43,6 @@
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_request.h>
#include <scsi/scsi_tcq.h>
#include <scsi/scsi_host.h>

157
drivers/scsi/scsi.c
View File

@ -63,7 +63,6 @@
#include <scsi/scsi_eh.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_tcq.h>
#include <scsi/scsi_request.h>
#include "scsi_priv.h"
#include "scsi_logging.h"
@ -116,79 +115,6 @@ const char *const scsi_device_types[MAX_SCSI_DEVICE_CODE] = {
};
EXPORT_SYMBOL(scsi_device_types);
/*
* Function: scsi_allocate_request
*
* Purpose: Allocate a request descriptor.
*
* Arguments: device - device for which we want a request
* gfp_mask - allocation flags passed to kmalloc
*
* Lock status: No locks assumed to be held. This function is SMP-safe.
*
* Returns: Pointer to request block.
*/
struct scsi_request *scsi_allocate_request(struct scsi_device *sdev,
gfp_t gfp_mask)
{
const int offset = ALIGN(sizeof(struct scsi_request), 4);
const int size = offset + sizeof(struct request);
struct scsi_request *sreq;
sreq = kzalloc(size, gfp_mask);
if (likely(sreq != NULL)) {
sreq->sr_request = (struct request *)(((char *)sreq) + offset);
sreq->sr_device = sdev;
sreq->sr_host = sdev->host;
sreq->sr_magic = SCSI_REQ_MAGIC;
sreq->sr_data_direction = DMA_BIDIRECTIONAL;
}
return sreq;
}
EXPORT_SYMBOL(scsi_allocate_request);
void __scsi_release_request(struct scsi_request *sreq)
{
struct request *req = sreq->sr_request;
/* unlikely because the tag was usually ended earlier by the
* mid-layer. However, for layering reasons ULD's don't end
* the tag of commands they generate. */
if (unlikely(blk_rq_tagged(req))) {
unsigned long flags;
struct request_queue *q = req->q;
spin_lock_irqsave(q->queue_lock, flags);
blk_queue_end_tag(q, req);
spin_unlock_irqrestore(q->queue_lock, flags);
}
if (likely(sreq->sr_command != NULL)) {
struct scsi_cmnd *cmd = sreq->sr_command;
sreq->sr_command = NULL;
scsi_next_command(cmd);
}
}
/*
* Function: scsi_release_request
*
* Purpose: Release a request descriptor.
*
* Arguments: sreq - request to release
*
* Lock status: No locks assumed to be held. This function is SMP-safe.
*/
void scsi_release_request(struct scsi_request *sreq)
{
__scsi_release_request(sreq);
kfree(sreq);
}
EXPORT_SYMBOL(scsi_release_request);
struct scsi_host_cmd_pool {
kmem_cache_t *slab;
unsigned int users;
@ -646,73 +572,6 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
return rtn;
}
/*
* Function: scsi_init_cmd_from_req
*
* Purpose: Queue a SCSI command
* Purpose: Initialize a struct scsi_cmnd from a struct scsi_request
*
* Arguments: cmd - command descriptor.
* sreq - Request from the queue.
*
* Lock status: None needed.
*
* Returns: Nothing.
*
* Notes: Mainly transfer data from the request structure to the
* command structure. The request structure is allocated
* using the normal memory allocator, and requests can pile
* up to more or less any depth. The command structure represents
* a consumable resource, as these are allocated into a pool
* when the SCSI subsystem initializes. The preallocation is
* required so that in low-memory situations a disk I/O request
* won't cause the memory manager to try and write out a page.
* The request structure is generally used by ioctls and character
* devices.
*/
void scsi_init_cmd_from_req(struct scsi_cmnd *cmd, struct scsi_request *sreq)
{
sreq->sr_command = cmd;
cmd->cmd_len = sreq->sr_cmd_len;
cmd->use_sg = sreq->sr_use_sg;
cmd->request = sreq->sr_request;
memcpy(cmd->data_cmnd, sreq->sr_cmnd, sizeof(cmd->data_cmnd));
cmd->serial_number = 0;
cmd->bufflen = sreq->sr_bufflen;
cmd->buffer = sreq->sr_buffer;
cmd->retries = 0;
cmd->allowed = sreq->sr_allowed;
cmd->done = sreq->sr_done;
cmd->timeout_per_command = sreq->sr_timeout_per_command;
cmd->sc_data_direction = sreq->sr_data_direction;
cmd->sglist_len = sreq->sr_sglist_len;
cmd->underflow = sreq->sr_underflow;
cmd->sc_request = sreq;
memcpy(cmd->cmnd, sreq->sr_cmnd, sizeof(sreq->sr_cmnd));
/*
* Zero the sense buffer. Some host adapters automatically request
* sense on error. 0 is not a valid sense code.
*/
memset(cmd->sense_buffer, 0, sizeof(sreq->sr_sense_buffer));
cmd->request_buffer = sreq->sr_buffer;
cmd->request_bufflen = sreq->sr_bufflen;
cmd->old_use_sg = cmd->use_sg;
if (cmd->cmd_len == 0)
cmd->cmd_len = COMMAND_SIZE(cmd->cmnd[0]);
cmd->old_cmd_len = cmd->cmd_len;
cmd->sc_old_data_direction = cmd->sc_data_direction;
cmd->old_underflow = cmd->underflow;
/*
* Start the timer ticking.
*/
cmd->result = 0;
SCSI_LOG_MLQUEUE(3, printk("Leaving scsi_init_cmd_from_req()\n"));
}
/*
* Per-CPU I/O completion queue.
@ -809,7 +668,6 @@ void scsi_finish_command(struct scsi_cmnd *cmd)
{
struct scsi_device *sdev = cmd->device;
struct Scsi_Host *shost = sdev->host;
struct scsi_request *sreq;
scsi_device_unbusy(sdev);
@ -839,21 +697,6 @@ void scsi_finish_command(struct scsi_cmnd *cmd)
* We can get here with use_sg=0, causing a panic in the upper level
*/
cmd->use_sg = cmd->old_use_sg;
/*
* If there is an associated request structure, copy the data over
* before we call the completion function.
*/
sreq = cmd->sc_request;
if (sreq) {
sreq->sr_result = sreq->sr_command->result;
if (sreq->sr_result) {
memcpy(sreq->sr_sense_buffer,
sreq->sr_command->sense_buffer,
sizeof(sreq->sr_sense_buffer));
}
}
cmd->done(cmd);
}
EXPORT_SYMBOL(scsi_finish_command);

1
drivers/scsi/scsi.h
View File

@ -25,7 +25,6 @@
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_request.h>
#include <scsi/scsi_tcq.h>
#include <scsi/scsi.h>

12
drivers/scsi/scsi_error.c
View File

@ -26,13 +26,13 @@
#include <linux/delay.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_dbg.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_transport.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/scsi_request.h>
#include "scsi_priv.h"
#include "scsi_logging.h"
@ -1671,8 +1671,6 @@ scsi_reset_provider(struct scsi_device *dev, int flag)
scmd->cmd_len = 0;
scmd->sc_data_direction = DMA_BIDIRECTIONAL;
scmd->sc_request = NULL;
scmd->sc_magic = SCSI_CMND_MAGIC;
init_timer(&scmd->eh_timeout);
@ -1769,14 +1767,6 @@ int scsi_normalize_sense(const u8 *sense_buffer, int sb_len,
}
EXPORT_SYMBOL(scsi_normalize_sense);
int scsi_request_normalize_sense(struct scsi_request *sreq,
struct scsi_sense_hdr *sshdr)
{
return scsi_normalize_sense(sreq->sr_sense_buffer,
sizeof(sreq->sr_sense_buffer), sshdr);
}
EXPORT_SYMBOL(scsi_request_normalize_sense);
int scsi_command_normalize_sense(struct scsi_cmnd *cmd,
struct scsi_sense_hdr *sshdr)
{

2
drivers/scsi/scsi_ioctl.c
View File

@ -15,11 +15,11 @@
#include <asm/uaccess.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/scsi_request.h>
#include <scsi/sg.h>
#include <scsi/scsi_dbg.h>

80
drivers/scsi/scsi_lib.c
View File

@ -19,12 +19,12 @@
#include <linux/hardirq.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_dbg.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_driver.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_request.h>
#include "scsi_priv.h"
#include "scsi_logging.h"
@ -83,7 +83,7 @@ static void scsi_unprep_request(struct request *req)
struct scsi_cmnd *cmd = req->special;
req->flags &= ~REQ_DONTPREP;
req->special = (req->flags & REQ_SPECIAL) ? cmd->sc_request : NULL;
req->special = NULL;
scsi_put_command(cmd);
}
@ -161,72 +161,6 @@ int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
return 0;
}
/*
* Function: scsi_do_req
*
* Purpose: Queue a SCSI request
*
* Arguments: sreq - command descriptor.
* cmnd - actual SCSI command to be performed.
* buffer - data buffer.
* bufflen - size of data buffer.
* done - completion function to be run.
* timeout - how long to let it run before timeout.
* retries - number of retries we allow.
*
* Lock status: No locks held upon entry.
*
* Returns: Nothing.
*
* Notes: This function is only used for queueing requests for things
* like ioctls and character device requests - this is because
* we essentially just inject a request into the queue for the
* device.
*
* In order to support the scsi_device_quiesce function, we
* now inject requests on the *head* of the device queue
* rather than the tail.
*/
void scsi_do_req(struct scsi_request *sreq, const void *cmnd,
void *buffer, unsigned bufflen,
void (*done)(struct scsi_cmnd *),
int timeout, int retries)
{
/*
* If the upper level driver is reusing these things, then
* we should release the low-level block now. Another one will
* be allocated later when this request is getting queued.
*/
__scsi_release_request(sreq);
/*
* Our own function scsi_done (which marks the host as not busy,
* disables the timeout counter, etc) will be called by us or by the
* scsi_hosts[host].queuecommand() function needs to also call
* the completion function for the high level driver.
*/
memcpy(sreq->sr_cmnd, cmnd, sizeof(sreq->sr_cmnd));
sreq->sr_bufflen = bufflen;
sreq->sr_buffer = buffer;
sreq->sr_allowed = retries;
sreq->sr_done = done;
sreq->sr_timeout_per_command = timeout;
if (sreq->sr_cmd_len == 0)
sreq->sr_cmd_len = COMMAND_SIZE(sreq->sr_cmnd[0]);
/*
* head injection *required* here otherwise quiesce won't work
*
* Because users of this function are apt to reuse requests with no
* modification, we have to sanitise the request flags here
*/
sreq->sr_request->flags &= ~REQ_DONTPREP;
blk_insert_request(sreq->sr_device->request_queue, sreq->sr_request,
1, sreq);
}
EXPORT_SYMBOL(scsi_do_req);
/**
* scsi_execute - insert request and wait for the result
* @sdev: scsi device
@ -1300,15 +1234,7 @@ static int scsi_prep_fn(struct request_queue *q, struct request *req)
* at request->cmd, as this tells us the real story.
*/
if (req->flags & REQ_SPECIAL && req->special) {
struct scsi_request *sreq = req->special;
if (sreq->sr_magic == SCSI_REQ_MAGIC) {
cmd = scsi_get_command(sreq->sr_device, GFP_ATOMIC);
if (unlikely(!cmd))
goto defer;
scsi_init_cmd_from_req(cmd, sreq);
} else
cmd = req->special;
cmd = req->special;
} else if (req->flags & (REQ_CMD | REQ_BLOCK_PC)) {
if(unlikely(specials_only) && !(req->flags & REQ_SPECIAL)) {

10
drivers/scsi/scsi_priv.h
View File

@ -8,16 +8,9 @@ struct request_queue;
struct scsi_cmnd;
struct scsi_device;
struct scsi_host_template;
struct scsi_request;
struct Scsi_Host;
/*
* Magic values for certain scsi structs. Shouldn't ever be used.
*/
#define SCSI_CMND_MAGIC 0xE25C23A5
#define SCSI_REQ_MAGIC 0x75F6D354
/*
* Scsi Error Handler Flags
*/
@ -34,9 +27,6 @@ extern void scsi_exit_hosts(void);
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);
extern void scsi_init_cmd_from_req(struct scsi_cmnd *cmd,
struct scsi_request *sreq);
extern void __scsi_release_request(struct scsi_request *sreq);
extern void __scsi_done(struct scsi_cmnd *cmd);
extern int scsi_retry_command(struct scsi_cmnd *cmd);
#ifdef CONFIG_SCSI_LOGGING

2
drivers/scsi/scsi_scan.c
View File

@ -33,11 +33,11 @@
#include <asm/semaphore.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_driver.h>
#include <scsi/scsi_devinfo.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_request.h>
#include <scsi/scsi_transport.h>
#include <scsi/scsi_eh.h>

1
drivers/scsi/scsi_typedefs.h
View File

@ -1,3 +1,2 @@
typedef struct scsi_cmnd Scsi_Cmnd;
typedef struct scsi_request Scsi_Request;

6
include/scsi/scsi_cmnd.h
View File

@ -9,7 +9,6 @@
struct request;
struct scatterlist;
struct scsi_device;
struct scsi_request;
/* embedded in scsi_cmnd */
@ -29,13 +28,8 @@ struct scsi_pointer {
};
struct scsi_cmnd {
int sc_magic;
struct scsi_device *device;
struct scsi_request *sc_request;
struct list_head list; /* scsi_cmnd participates in queue lists */
struct list_head eh_entry; /* entry for the host eh_cmd_q */
int eh_eflags; /* Used by error handlr */
void (*done) (struct scsi_cmnd *); /* Mid-level done function */

2
include/scsi/scsi_dbg.h
View File

@ -2,14 +2,12 @@
#define _SCSI_SCSI_DBG_H
struct scsi_cmnd;
struct scsi_request;
struct scsi_sense_hdr;
extern void scsi_print_command(struct scsi_cmnd *);
extern void scsi_print_sense_hdr(const char *, struct scsi_sense_hdr *);
extern void __scsi_print_command(unsigned char *);
extern void scsi_print_sense(const char *, struct scsi_cmnd *);
extern void scsi_print_req_sense(const char *, struct scsi_request *);
extern void __scsi_print_sense(const char *name,
const unsigned char *sense_buffer,
int sense_len);

3
include/scsi/scsi_eh.h
View File

@ -3,7 +3,6 @@
struct scsi_cmnd;
struct scsi_device;
struct scsi_request;
struct Scsi_Host;
/*
@ -43,8 +42,6 @@ extern void scsi_report_device_reset(struct Scsi_Host *, int, int);
extern int scsi_block_when_processing_errors(struct scsi_device *);
extern int scsi_normalize_sense(const u8 *sense_buffer, int sb_len,
struct scsi_sense_hdr *sshdr);
extern int scsi_request_normalize_sense(struct scsi_request *sreq,
struct scsi_sense_hdr *sshdr);
extern int scsi_command_normalize_sense(struct scsi_cmnd *cmd,
struct scsi_sense_hdr *sshdr);

54
include/scsi/scsi_request.h
View File

@ -1,54 +0,0 @@
#ifndef _SCSI_SCSI_REQUEST_H
#define _SCSI_SCSI_REQUEST_H
#include <scsi/scsi_cmnd.h>
struct request;
struct scsi_cmnd;
struct scsi_device;
struct Scsi_Host;
/*
* This is essentially a slimmed down version of Scsi_Cmnd. The point of
* having this is that requests that are injected into the queue as result
* of things like ioctls and character devices shouldn't be using a
* Scsi_Cmnd until such a time that the command is actually at the head
* of the queue and being sent to the driver.
*/
struct scsi_request {
int sr_magic;
int sr_result; /* Status code from lower level driver */
unsigned char sr_sense_buffer[SCSI_SENSE_BUFFERSIZE]; /* obtained by REQUEST SENSE
* when CHECK CONDITION is
* received on original command
* (auto-sense) */
struct Scsi_Host *sr_host;
struct scsi_device *sr_device;
struct scsi_cmnd *sr_command;
struct request *sr_request; /* A copy of the command we are
working on */
unsigned sr_bufflen; /* Size of data buffer */
void *sr_buffer; /* Data buffer */
int sr_allowed;
enum dma_data_direction sr_data_direction;
unsigned char sr_cmd_len;
unsigned char sr_cmnd[MAX_COMMAND_SIZE];
void (*sr_done) (struct scsi_cmnd *); /* Mid-level done function */
int sr_timeout_per_command;
unsigned short sr_use_sg; /* Number of pieces of scatter-gather */
unsigned short sr_sglist_len; /* size of malloc'd scatter-gather list */
unsigned sr_underflow; /* Return error if less than
this amount is transferred */
void *upper_private_data; /* reserved for owner (usually upper
level driver) of this request */
};
extern struct scsi_request *scsi_allocate_request(struct scsi_device *, gfp_t);
extern void scsi_release_request(struct scsi_request *);
extern void scsi_do_req(struct scsi_request *, const void *cmnd,
void *buffer, unsigned bufflen,
void (*done) (struct scsi_cmnd *),
int timeout, int retries);
#endif /* _SCSI_SCSI_REQUEST_H */

26
include/scsi/sg_request.h
View File

@ -1,26 +0,0 @@
typedef struct scsi_request Scsi_Request;
static Scsi_Request *dummy_cmdp; /* only used for sizeof */
typedef struct sg_scatter_hold { /* holding area for scsi scatter gather info */
unsigned short k_use_sg; /* Count of kernel scatter-gather pieces */
unsigned short sglist_len; /* size of malloc'd scatter-gather list ++ */
unsigned bufflen; /* Size of (aggregate) data buffer */
unsigned b_malloc_len; /* actual len malloc'ed in buffer */
void *buffer; /* Data buffer or scatter list (k_use_sg>0) */
char dio_in_use; /* 0->indirect IO (or mmap), 1->dio */
unsigned char cmd_opcode; /* first byte of command */
} Sg_scatter_hold;
typedef struct sg_request { /* SG_MAX_QUEUE requests outstanding per file */
Scsi_Request *my_cmdp; /* != 0 when request with lower levels */
struct sg_request *nextrp; /* NULL -> tail request (slist) */
struct sg_fd *parentfp; /* NULL -> not in use */
Sg_scatter_hold data; /* hold buffer, perhaps scatter list */
sg_io_hdr_t header; /* scsi command+info, see <scsi/sg.h> */
unsigned char sense_b[sizeof (dummy_cmdp->sr_sense_buffer)];
char res_used; /* 1 -> using reserve buffer, 0 -> not ... */
char orphan; /* 1 -> drop on sight, 0 -> normal */
char sg_io_owned; /* 1 -> packet belongs to SG_IO */
volatile char done; /* 0->before bh, 1->before read, 2->read */
} Sg_request;