Merge with 2.5.75.

[linux-2.6/linux-mips.git] / drivers / scsi / scsi.c

/*
 *  scsi.c Copyright (C) 1992 Drew Eckhardt
 *         Copyright (C) 1993, 1994, 1995, 1999 Eric Youngdale
 *
 *  generic mid-level SCSI driver
 *      Initial versions: Drew Eckhardt
 *      Subsequent revisions: Eric Youngdale
 *
 *  <drew@colorado.edu>
 *
 *  Bug correction thanks go to :
 *      Rik Faith <faith@cs.unc.edu>
 *      Tommy Thorn <tthorn>
 *      Thomas Wuensche <tw@fgb1.fgb.mw.tu-muenchen.de>
 *
 *  Modified by Eric Youngdale eric@andante.org or ericy@gnu.ai.mit.edu to
 *  add scatter-gather, multiple outstanding request, and other
 *  enhancements.
 *
 *  Native multichannel, wide scsi, /proc/scsi and hot plugging
 *  support added by Michael Neuffer <mike@i-connect.net>
 *
 *  Added request_module("scsi_hostadapter") for kerneld:
 *  (Put an "alias scsi_hostadapter your_hostadapter" in /etc/modules.conf)
 *  Bjorn Ekwall  <bj0rn@blox.se>
 *  (changed to kmod)
 *
 *  Major improvements to the timeout, abort, and reset processing,
 *  as well as performance modifications for large queue depths by
 *  Leonard N. Zubkoff <lnz@dandelion.com>
 *
 *  Converted cli() code to spinlocks, Ingo Molnar
 *
 *  Jiffies wrap fixes (host->resetting), 3 Dec 1998 Andrea Arcangeli
 *
 *  out_of_space hacks, D. Gilbert (dpg) 990608
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/unistd.h>
#include <linux/spinlock.h>
#include <linux/kmod.h>
#include <linux/interrupt.h>

#include "scsi.h"
#include "hosts.h"

#include "scsi_priv.h"
#include "scsi_logging.h"


/*
 * Definitions and constants.
 */

#define MIN_RESET_DELAY (2*HZ)

/* Do not call reset on error if we just did a reset within 15 sec. */
#define MIN_RESET_PERIOD (15*HZ)

/*
 * Macro to determine the size of SCSI command. This macro takes vendor
 * unique commands into account. SCSI commands in groups 6 and 7 are
 * vendor unique and we will depend upon the command length being
 * supplied correctly in cmd_len.
 */
#define CDB_SIZE(cmd)   (((((cmd)->cmnd[0] >> 5) & 7) < 6) ? \
                                COMMAND_SIZE((cmd)->cmnd[0]) : (cmd)->cmd_len)

/*
 * Data declarations.
 */
unsigned long scsi_pid;
static unsigned long serial_number;

/*
 * Note - the initial logging level can be set here to log events at boot time.
 * After the system is up, you may enable logging via the /proc interface.
 */
unsigned int scsi_logging_level;

const char *const scsi_device_types[MAX_SCSI_DEVICE_CODE] = {
        "Direct-Access    ",
        "Sequential-Access",
        "Printer          ",
        "Processor        ",
        "WORM             ",
        "CD-ROM           ",
        "Scanner          ",
        "Optical Device   ",
        "Medium Changer   ",
        "Communications   ",
        "Unknown          ",
        "Unknown          ",
        "Unknown          ",
        "Enclosure        ",
};

/*
 * Function:    scsi_allocate_request
 *
 * Purpose:     Allocate a request descriptor.
 *
 * Arguments:   device    - device for which we want a request
 *
 * Lock status: No locks assumed to be held.  This function is SMP-safe.
 *
 * Returns:     Pointer to request block.
 *
 * Notes:       With the new queueing code, it becomes important
 *              to track the difference between a command and a
 *              request.  A request is a pending item in the queue that
 *              has not yet reached the top of the queue.
 *
 * XXX(hch):    Need to add a gfp_mask argument.
 */
struct scsi_request *scsi_allocate_request(struct scsi_device *sdev)
{
        const int offset = ALIGN(sizeof(struct scsi_request), 4);
        const int size = offset + sizeof(struct request);
        struct scsi_request *sreq;
  
        sreq = kmalloc(size, GFP_ATOMIC);
        if (likely(sreq != NULL)) {
                memset(sreq, 0, size);
                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;
}

void __scsi_release_request(struct scsi_request *sreq)
{
        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);
}

struct scsi_host_cmd_pool {
        kmem_cache_t    *slab;
        unsigned int    users;
        char            *name;
        unsigned int    slab_flags;
        unsigned int    gfp_mask;
};

static struct scsi_host_cmd_pool scsi_cmd_pool = {
        .name           = "scsi_cmd_cache",
        .slab_flags     = SLAB_HWCACHE_ALIGN,
};

static struct scsi_host_cmd_pool scsi_cmd_dma_pool = {
        .name           = "scsi_cmd_cache(DMA)",
        .slab_flags     = SLAB_HWCACHE_ALIGN|SLAB_CACHE_DMA,
        .gfp_mask       = __GFP_DMA,
};

static DECLARE_MUTEX(host_cmd_pool_mutex);

static struct scsi_cmnd *__scsi_get_command(struct Scsi_Host *shost,
                                            int gfp_mask)
{
        struct scsi_cmnd *cmd;

        cmd = kmem_cache_alloc(shost->cmd_pool->slab,
                        gfp_mask | shost->cmd_pool->gfp_mask);

        if (unlikely(!cmd)) {
                unsigned long flags;

                spin_lock_irqsave(&shost->free_list_lock, flags);
                if (likely(!list_empty(&shost->free_list))) {
                        cmd = list_entry(shost->free_list.next,
                                         struct scsi_cmnd, list);
                        list_del_init(&cmd->list);
                }
                spin_unlock_irqrestore(&shost->free_list_lock, flags);
        }

        return cmd;
}

/*
 * Function:    scsi_get_command()
 *
 * Purpose:     Allocate and setup a scsi command block
 *
 * Arguments:   dev     - parent scsi device
 *              gfp_mask- allocator flags
 *
 * Returns:     The allocated scsi command structure.
 */
struct scsi_cmnd *scsi_get_command(struct scsi_device *dev, int gfp_mask)
{
        struct scsi_cmnd *cmd = __scsi_get_command(dev->host, gfp_mask);

        if (likely(cmd != NULL)) {
                unsigned long flags;

                memset(cmd, 0, sizeof(*cmd));
                cmd->device = dev;
                cmd->state = SCSI_STATE_UNUSED;
                cmd->owner = SCSI_OWNER_NOBODY;
                init_timer(&cmd->eh_timeout);
                INIT_LIST_HEAD(&cmd->list);
                spin_lock_irqsave(&dev->list_lock, flags);
                list_add_tail(&cmd->list, &dev->cmd_list);
                spin_unlock_irqrestore(&dev->list_lock, flags);
        }

        return cmd;
}                               

/*
 * Function:    scsi_put_command()
 *
 * Purpose:     Free a scsi command block
 *
 * Arguments:   cmd     - command block to free
 *
 * Returns:     Nothing.
 *
 * Notes:       The command must not belong to any lists.
 */
void scsi_put_command(struct scsi_cmnd *cmd)
{
        struct Scsi_Host *shost = cmd->device->host;
        unsigned long flags;
        
        /* serious error if the command hasn't come from a device list */
        spin_lock_irqsave(&cmd->device->list_lock, flags);
        BUG_ON(list_empty(&cmd->list));
        list_del_init(&cmd->list);
        spin_unlock(&cmd->device->list_lock);
        /* changing locks here, don't need to restore the irq state */
        spin_lock(&shost->free_list_lock);
        if (unlikely(list_empty(&shost->free_list))) {
                list_add(&cmd->list, &shost->free_list);
                cmd = NULL;
        }
        spin_unlock_irqrestore(&shost->free_list_lock, flags);

        if (likely(cmd != NULL))
                kmem_cache_free(shost->cmd_pool->slab, cmd);
}

/*
 * Function:    scsi_setup_command_freelist()
 *
 * Purpose:     Setup the command freelist for a scsi host.
 *
 * Arguments:   shost   - host to allocate the freelist for.
 *
 * Returns:     Nothing.
 */
int scsi_setup_command_freelist(struct Scsi_Host *shost)
{
        struct scsi_host_cmd_pool *pool;
        struct scsi_cmnd *cmd;

        spin_lock_init(&shost->free_list_lock);
        INIT_LIST_HEAD(&shost->free_list);

        /*
         * Select a command slab for this host and create it if not
         * yet existant.
         */
        down(&host_cmd_pool_mutex);
        pool = (shost->unchecked_isa_dma ? &scsi_cmd_dma_pool : &scsi_cmd_pool);
        if (!pool->users) {
                pool->slab = kmem_cache_create(pool->name,
                                sizeof(struct scsi_cmnd), 0,
                                pool->slab_flags, NULL, NULL);
                if (!pool->slab)
                        goto fail;
        }

        pool->users++;
        shost->cmd_pool = pool;
        up(&host_cmd_pool_mutex);

        /*
         * Get one backup command for this host.
         */
        cmd = kmem_cache_alloc(shost->cmd_pool->slab,
                        GFP_KERNEL | shost->cmd_pool->gfp_mask);
        if (!cmd)
                goto fail2;
        list_add(&cmd->list, &shost->free_list);                
        return 0;

 fail2:
        if (!--pool->users)
                kmem_cache_destroy(pool->slab);
        return -ENOMEM;
 fail:
        up(&host_cmd_pool_mutex);
        return -ENOMEM;

}

/*
 * Function:    scsi_destroy_command_freelist()
 *
 * Purpose:     Release the command freelist for a scsi host.
 *
 * Arguments:   shost   - host that's freelist is going to be destroyed
 */
void scsi_destroy_command_freelist(struct Scsi_Host *shost)
{
        while (!list_empty(&shost->free_list)) {
                struct scsi_cmnd *cmd;

                cmd = list_entry(shost->free_list.next, struct scsi_cmnd, list);
                list_del_init(&cmd->list);
                kmem_cache_free(shost->cmd_pool->slab, cmd);
        }

        down(&host_cmd_pool_mutex);
        if (!--shost->cmd_pool->users)
                kmem_cache_destroy(shost->cmd_pool->slab);
        up(&host_cmd_pool_mutex);
}

/*
 * Function:    scsi_dispatch_command
 *
 * Purpose:     Dispatch a command to the low-level driver.
 *
 * Arguments:   cmd - command block we are dispatching.
 *
 * Notes:
 */
int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
{
        struct Scsi_Host *host = cmd->device->host;
        unsigned long flags = 0;
        unsigned long timeout;
        int rtn = 1;

        /* Assign a unique nonzero serial_number. */
        /* XXX(hch): this is racy */
        if (++serial_number == 0)
                serial_number = 1;
        cmd->serial_number = serial_number;
        cmd->pid = scsi_pid++;

        /* 
         * If SCSI-2 or lower, store the LUN value in cmnd.
         */
        if (cmd->device->scsi_level <= SCSI_2) {
                cmd->cmnd[1] = (cmd->cmnd[1] & 0x1f) |
                               (cmd->device->lun << 5 & 0xe0);
        }

        /*
         * We will wait MIN_RESET_DELAY clock ticks after the last reset so
         * we can avoid the drive not being ready.
         */
        timeout = host->last_reset + MIN_RESET_DELAY;

        if (host->resetting && time_before(jiffies, timeout)) {
                int ticks_remaining = timeout - jiffies;
                /*
                 * NOTE: This may be executed from within an interrupt
                 * handler!  This is bad, but for now, it'll do.  The irq
                 * level of the interrupt handler has been masked out by the
                 * platform dependent interrupt handling code already, so the
                 * sti() here will not cause another call to the SCSI host's
                 * interrupt handler (assuming there is one irq-level per
                 * host).
                 */
                while (--ticks_remaining >= 0)
                        mdelay(1 + 999 / HZ);
                host->resetting = 0;
        }

        scsi_add_timer(cmd, cmd->timeout_per_command, scsi_times_out);

        /*
         * We will use a queued command if possible, otherwise we will
         * emulate the queuing and calling of completion function ourselves.
         */
        SCSI_LOG_MLQUEUE(3, printk("scsi_dispatch_cmnd (host = %d, "
                                "channel = %d, target = %d, command = %p, "
                                "buffer = %p, \nbufflen = %d, done = %p)\n",
                                host->host_no, cmd->device->channel,
                                cmd->device->id, cmd->cmnd, cmd->buffer,
                                cmd->bufflen, cmd->done));

        cmd->state = SCSI_STATE_QUEUED;
        cmd->owner = SCSI_OWNER_LOWLEVEL;

        /*
         * Before we queue this command, check if the command
         * length exceeds what the host adapter can handle.
         */
        if (CDB_SIZE(cmd) > cmd->device->host->max_cmd_len) {
                SCSI_LOG_MLQUEUE(3,
                                printk("queuecommand : command too long.\n"));
                cmd->result = (DID_ABORT << 16);

                spin_lock_irqsave(host->host_lock, flags);
                scsi_done(cmd);
                spin_unlock_irqrestore(host->host_lock, flags);
                goto out;
        }

        SCSI_LOG_MLQUEUE(3, printk("queuecommand : routine at %p\n",
                                   host->hostt->queuecommand));

        spin_lock_irqsave(host->host_lock, flags);
        rtn = host->hostt->queuecommand(cmd, scsi_done);
        spin_unlock_irqrestore(host->host_lock, flags);
        if (rtn) {
                scsi_queue_insert(cmd,
                                (rtn == SCSI_MLQUEUE_DEVICE_BUSY) ?
                                 rtn : SCSI_MLQUEUE_HOST_BUSY);
                SCSI_LOG_MLQUEUE(3,
                    printk("queuecommand : request rejected\n"));
        }

 out:
        SCSI_LOG_MLQUEUE(3, printk("leaving scsi_dispatch_cmnd()\n"));
        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->owner = SCSI_OWNER_MIDLEVEL;
        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->serial_number_at_timeout = 0;
        cmd->bufflen = sreq->sr_bufflen;
        cmd->buffer = sreq->sr_buffer;
        cmd->flags = 0;
        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->internal_timeout = NORMAL_TIMEOUT;
        cmd->abort_reason = 0;
        cmd->result = 0;

        SCSI_LOG_MLQUEUE(3, printk("Leaving scsi_init_cmd_from_req()\n"));
}

/*
 * Per-CPU I/O completion queue.
 */
static struct list_head done_q[NR_CPUS] __cacheline_aligned;

/**
 * scsi_done - Enqueue the finished SCSI command into the done queue.
 * @cmd: The SCSI Command for which a low-level device driver (LLDD) gives
 * ownership back to SCSI Core -- i.e. the LLDD has finished with it.
 *
 * This function is the mid-level's (SCSI Core) interrupt routine, which
 * regains ownership of the SCSI command (de facto) from a LLDD, and enqueues
 * the command to the done queue for further processing.
 *
 * This is the producer of the done queue who enqueues at the tail.
 *
 * This function is interrupt context safe.
 */
void scsi_done(struct scsi_cmnd *cmd)
{
        unsigned long flags;
        int cpu;

        /*
         * We don't have to worry about this one timing out any more.
         * If we are unable to remove the timer, then the command
         * has already timed out.  In which case, we have no choice but to
         * let the timeout function run, as we have no idea where in fact
         * that function could really be.  It might be on another processor,
         * etc, etc.
         */
        if (!scsi_delete_timer(cmd))
                return;

        /*
         * Set the serial numbers back to zero
         */
        cmd->serial_number = 0;
        cmd->serial_number_at_timeout = 0;
        cmd->state = SCSI_STATE_BHQUEUE;
        cmd->owner = SCSI_OWNER_BH_HANDLER;

        /*
         * Next, enqueue the command into the done queue.
         * It is a per-CPU queue, so we just disable local interrupts
         * and need no spinlock.
         */
        local_irq_save(flags);
        cpu = smp_processor_id();
        list_add_tail(&cmd->eh_entry, &done_q[cpu]);
        raise_softirq_irqoff(SCSI_SOFTIRQ);
        local_irq_restore(flags);
}

/**
 * scsi_softirq - Perform post-interrupt processing of finished SCSI commands.
 *
 * This is the consumer of the done queue.
 *
 * This is called with all interrupts enabled.  This should reduce
 * interrupt latency, stack depth, and reentrancy of the low-level
 * drivers.
 */
static void scsi_softirq(struct softirq_action *h)
{
        LIST_HEAD(local_q);

        local_irq_disable();
        list_splice_init(&done_q[smp_processor_id()], &local_q);
        local_irq_enable();

        while (!list_empty(&local_q)) {
                struct scsi_cmnd *cmd = list_entry(local_q.next,
                                                   struct scsi_cmnd, eh_entry);
                list_del_init(&cmd->eh_entry);

                switch (scsi_decide_disposition(cmd)) {
                case SUCCESS:
                        /*
                         * Add to BH queue.
                         */
                        SCSI_LOG_MLCOMPLETE(3,
                                            printk("Command finished %d %d "
                                                   "0x%x\n",
                                           cmd->device->host->host_busy,
                                           cmd->device->host->host_failed,
                                                   cmd->result));

                        scsi_finish_command(cmd);
                        break;
                case NEEDS_RETRY:
                        /*
                         * We only come in here if we want to retry a
                         * command.  The test to see whether the
                         * command should be retried should be keeping
                         * track of the number of tries, so we don't
                         * end up looping, of course.
                         */
                        SCSI_LOG_MLCOMPLETE(3, printk("Command needs retry "
                                                      "%d %d 0x%x\n",
                                              cmd->device->host->host_busy,
                                              cmd->device->host->host_failed,
                                                      cmd->result));

                        scsi_retry_command(cmd);
                        break;
                case ADD_TO_MLQUEUE:
                        /* 
                         * This typically happens for a QUEUE_FULL
                         * message - typically only when the queue
                         * depth is only approximate for a given
                         * device.  Adding a command to the queue for
                         * the device will prevent further commands
                         * from being sent to the device, so we
                         * shouldn't end up with tons of things being
                         * sent down that shouldn't be.
                         */
                        SCSI_LOG_MLCOMPLETE(3, printk("Command rejected as "
                                                      "device queue full, "
                                                      "put on ml queue %p\n",
                                                      cmd));
                        scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
                        break;
                default:
                        /*
                         * Here we have a fatal error of some sort.
                         * Turn it over to the error handler.
                         */
                        SCSI_LOG_MLCOMPLETE(3,
                                            printk("Command failed %p %x "
                                                   "busy=%d failed=%d\n",
                                                   cmd, cmd->result,
                                           cmd->device->host->host_busy,
                                           cmd->device->host->host_failed));

                        /*
                         * Dump the sense information too.
                         */
                        if (status_byte(cmd->result) & CHECK_CONDITION)
                                SCSI_LOG_MLCOMPLETE(3, print_sense("bh", cmd));

                        /*
                         * We only fail here if the error recovery thread
                         * has died.
                         */
                        if (!scsi_eh_scmd_add(cmd, 0))
                                scsi_finish_command(cmd);
                }
        }
}

/*
 * Function:    scsi_retry_command
 *
 * Purpose:     Send a command back to the low level to be retried.
 *
 * Notes:       This command is always executed in the context of the
 *              bottom half handler, or the error handler thread. Low
 *              level drivers should not become re-entrant as a result of
 *              this.
 */
int scsi_retry_command(struct scsi_cmnd *cmd)
{
        /*
         * Restore the SCSI command state.
         */
        scsi_setup_cmd_retry(cmd);

        /*
         * Zero the sense information from the last time we tried
         * this command.
         */
        memset(cmd->sense_buffer, 0, sizeof(cmd->sense_buffer));

        return scsi_dispatch_cmd(cmd);
}

/*
 * Function:    scsi_finish_command
 *
 * Purpose:     Pass command off to upper layer for finishing of I/O
 *              request, waking processes that are waiting on results,
 *              etc.
 */
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);

        /*
         * Clear the flags which say that the device/host is no longer
         * capable of accepting new commands.  These are set in scsi_queue.c
         * for both the queue full condition on a device, and for a
         * host full condition on the host.
         *
         * XXX(hch): What about locking?
         */
        shost->host_blocked = 0;
        sdev->device_blocked = 0;

        /*
         * If we have valid sense information, then some kind of recovery
         * must have taken place.  Make a note of this.
         */
        if (SCSI_SENSE_VALID(cmd))
                cmd->result |= (DRIVER_SENSE << 24);

        SCSI_LOG_MLCOMPLETE(3, printk("Notifying upper driver of completion "
                                "for device %d %x\n", sdev->id, cmd->result));

        cmd->owner = SCSI_OWNER_HIGHLEVEL;
        cmd->state = SCSI_STATE_FINISHED;

        /*
         * 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);
}

/*
 * Function:    scsi_adjust_queue_depth()
 *
 * Purpose:     Allow low level drivers to tell us to change the queue depth
 *              on a specific SCSI device
 *
 * Arguments:   sdev    - SCSI Device in question
 *              tagged  - Do we use tagged queueing (non-0) or do we treat
 *                        this device as an untagged device (0)
 *              tags    - Number of tags allowed if tagged queueing enabled,
 *                        or number of commands the low level driver can
 *                        queue up in non-tagged mode (as per cmd_per_lun).
 *
 * Returns:     Nothing
 *
 * Lock Status: None held on entry
 *
 * Notes:       Low level drivers may call this at any time and we will do
 *              the right thing depending on whether or not the device is
 *              currently active and whether or not it even has the
 *              command blocks built yet.
 *
 * XXX(hch):    What exactly is device_request_lock trying to protect?
 */
void scsi_adjust_queue_depth(struct scsi_device *sdev, int tagged, int tags)
{
        static spinlock_t device_request_lock = SPIN_LOCK_UNLOCKED;
        unsigned long flags;

        /*
         * refuse to set tagged depth to an unworkable size
         */
        if (tags <= 0)
                return;
        /*
         * Limit max queue depth on a single lun to 256 for now.  Remember,
         * we allocate a struct scsi_command for each of these and keep it
         * around forever.  Too deep of a depth just wastes memory.
         */
        if (tags > 256)
                return;

        spin_lock_irqsave(&device_request_lock, flags);
        sdev->queue_depth = tags;
        switch (tagged) {
                case MSG_ORDERED_TAG:
                        sdev->ordered_tags = 1;
                        sdev->simple_tags = 1;
                        break;
                case MSG_SIMPLE_TAG:
                        sdev->ordered_tags = 0;
                        sdev->simple_tags = 1;
                        break;
                default:
                        printk(KERN_WARNING "(scsi%d:%d:%d:%d) "
                                "scsi_adjust_queue_depth, bad queue type, "
                                "disabled\n", sdev->host->host_no,
                                sdev->channel, sdev->id, sdev->lun); 
                case 0:
                        sdev->ordered_tags = sdev->simple_tags = 0;
                        sdev->queue_depth = tags;
                        break;
        }
        spin_unlock_irqrestore(&device_request_lock, flags);
}

/*
 * Function:    scsi_track_queue_full()
 *
 * Purpose:     This function will track successive QUEUE_FULL events on a
 *              specific SCSI device to determine if and when there is a
 *              need to adjust the queue depth on the device.
 *
 * Arguments:   sdev    - SCSI Device in question
 *              depth   - Current number of outstanding SCSI commands on
 *                        this device, not counting the one returned as
 *                        QUEUE_FULL.
 *
 * Returns:     0 - No change needed
 *              >0 - Adjust queue depth to this new depth
 *              -1 - Drop back to untagged operation using host->cmd_per_lun
 *                      as the untagged command depth
 *
 * Lock Status: None held on entry
 *
 * Notes:       Low level drivers may call this at any time and we will do
 *              "The Right Thing."  We are interrupt context safe.
 */
int scsi_track_queue_full(struct scsi_device *sdev, int depth)
{
        if ((jiffies >> 4) == sdev->last_queue_full_time)
                return 0;

        sdev->last_queue_full_time = (jiffies >> 4);
        if (sdev->last_queue_full_depth != depth) {
                sdev->last_queue_full_count = 1;
                sdev->last_queue_full_depth = depth;
        } else {
                sdev->last_queue_full_count++;
        }

        if (sdev->last_queue_full_count <= 10)
                return 0;
        if (sdev->last_queue_full_depth < 8) {
                /* Drop back to untagged */
                scsi_adjust_queue_depth(sdev, 0, sdev->host->cmd_per_lun);
                return -1;
        }
        
        if (sdev->ordered_tags)
                scsi_adjust_queue_depth(sdev, MSG_ORDERED_TAG, depth);
        else
                scsi_adjust_queue_depth(sdev, MSG_SIMPLE_TAG, depth);
        return depth;
}

int scsi_device_get(struct scsi_device *sdev)
{
        if (!try_module_get(sdev->host->hostt->module))
                return -ENXIO;

        sdev->access_count++;
        return 0;
}

void scsi_device_put(struct scsi_device *sdev)
{
        sdev->access_count--;
        module_put(sdev->host->hostt->module);
}

/**
 * scsi_set_device_offline - set scsi_device offline
 * @sdev:       pointer to struct scsi_device to offline. 
 *
 * Locks:       host_lock held on entry.
 **/
void scsi_set_device_offline(struct scsi_device *sdev)
{
        struct scsi_cmnd *scmd;
        LIST_HEAD(active_list);
        struct list_head *lh, *lh_sf;
        unsigned long flags;

        sdev->online = 0;

        spin_lock_irqsave(&sdev->list_lock, flags);
        list_for_each_entry(scmd, &sdev->cmd_list, list) {
                if (scmd->request && scmd->request->rq_status != RQ_INACTIVE) {
                        /*
                         * If we are unable to remove the timer, it means
                         * that the command has already timed out or
                         * finished.
                         */
                        if (!scsi_delete_timer(scmd))
                                continue;
                        list_add_tail(&scmd->eh_entry, &active_list);
                }
        }
        spin_unlock_irqrestore(&sdev->list_lock, flags);

        if (!list_empty(&active_list)) {
                list_for_each_safe(lh, lh_sf, &active_list) {
                        scmd = list_entry(lh, struct scsi_cmnd, eh_entry);
                        scsi_eh_scmd_add(scmd, SCSI_EH_CANCEL_CMD);
                }
        } else {
                /* FIXME: Send online state change hotplug event */
        }
}

MODULE_DESCRIPTION("SCSI core");
MODULE_LICENSE("GPL");

module_param(scsi_logging_level, int, S_IRUGO|S_IWUSR);
MODULE_PARM_DESC(scsi_logging_level, "a bit mask of logging levels");

static int __init init_scsi(void)
{
        int error, i;

        error = scsi_init_queue();
        if (error)
                return error;
        error = scsi_init_procfs();
        if (error)
                goto cleanup_queue;
        error = scsi_init_devinfo();
        if (error)
                goto cleanup_procfs;
        error = scsi_sysfs_register();
        if (error)
                goto cleanup_devlist;

        for (i = 0; i < NR_CPUS; i++)
                INIT_LIST_HEAD(&done_q[i]);

        devfs_mk_dir("scsi");
        open_softirq(SCSI_SOFTIRQ, scsi_softirq, NULL);
        printk(KERN_NOTICE "SCSI subsystem initialized\n");
        return 0;

cleanup_devlist:
        scsi_exit_devinfo();
cleanup_procfs:
        scsi_exit_procfs();
cleanup_queue:
        scsi_exit_queue();
        printk(KERN_ERR "SCSI subsystem failed to initialize, error = %d\n",
               -error);
        return error;
}

static void __exit exit_scsi(void)
{
        scsi_sysfs_unregister();
        scsi_exit_devinfo();
        devfs_remove("scsi");
        scsi_exit_procfs();
        scsi_exit_queue();
}

subsys_initcall(init_scsi);
module_exit(exit_scsi);