linux/drivers/scsi/scsi_lib.c
Jun'ichi Nomura b7e94a1686 [SCSI] Fix dm-multipath starvation when scsi host is busy
block congestion control doesn't have any concept of fairness across
multiple queues.  This means that if SCSI reports the host as busy in
the queue congestion control it can result in an unfair starvation
situation in dm-mp if there are multiple multipath devices on the same
host.  For example:
http://www.redhat.com/archives/dm-devel/2012-May/msg00123.html

The fix for this is to report only the sdev busy state (and ignore the
host busy state) in the block congestion control call back.
The host is still congested, but the SCSI subsystem will sort out the
congestion in a fair way because it knows the relation between the
queues and the host.

[jejb: fixed up trailing whitespace]
Reported-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Tested-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
2012-05-23 09:34:17 +01:00

2590 lines
65 KiB
C

/*
* scsi_lib.c Copyright (C) 1999 Eric Youngdale
*
* SCSI queueing library.
* Initial versions: Eric Youngdale (eric@andante.org).
* Based upon conversations with large numbers
* of people at Linux Expo.
*/
#include <linux/bio.h>
#include <linux/bitops.h>
#include <linux/blkdev.h>
#include <linux/completion.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/mempool.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/delay.h>
#include <linux/hardirq.h>
#include <linux/scatterlist.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_priv.h"
#include "scsi_logging.h"
#define SG_MEMPOOL_NR ARRAY_SIZE(scsi_sg_pools)
#define SG_MEMPOOL_SIZE 2
struct scsi_host_sg_pool {
size_t size;
char *name;
struct kmem_cache *slab;
mempool_t *pool;
};
#define SP(x) { x, "sgpool-" __stringify(x) }
#if (SCSI_MAX_SG_SEGMENTS < 32)
#error SCSI_MAX_SG_SEGMENTS is too small (must be 32 or greater)
#endif
static struct scsi_host_sg_pool scsi_sg_pools[] = {
SP(8),
SP(16),
#if (SCSI_MAX_SG_SEGMENTS > 32)
SP(32),
#if (SCSI_MAX_SG_SEGMENTS > 64)
SP(64),
#if (SCSI_MAX_SG_SEGMENTS > 128)
SP(128),
#if (SCSI_MAX_SG_SEGMENTS > 256)
#error SCSI_MAX_SG_SEGMENTS is too large (256 MAX)
#endif
#endif
#endif
#endif
SP(SCSI_MAX_SG_SEGMENTS)
};
#undef SP
struct kmem_cache *scsi_sdb_cache;
/*
* When to reinvoke queueing after a resource shortage. It's 3 msecs to
* not change behaviour from the previous unplug mechanism, experimentation
* may prove this needs changing.
*/
#define SCSI_QUEUE_DELAY 3
/*
* Function: scsi_unprep_request()
*
* Purpose: Remove all preparation done for a request, including its
* associated scsi_cmnd, so that it can be requeued.
*
* Arguments: req - request to unprepare
*
* Lock status: Assumed that no locks are held upon entry.
*
* Returns: Nothing.
*/
static void scsi_unprep_request(struct request *req)
{
struct scsi_cmnd *cmd = req->special;
blk_unprep_request(req);
req->special = NULL;
scsi_put_command(cmd);
}
/**
* __scsi_queue_insert - private queue insertion
* @cmd: The SCSI command being requeued
* @reason: The reason for the requeue
* @unbusy: Whether the queue should be unbusied
*
* This is a private queue insertion. The public interface
* scsi_queue_insert() always assumes the queue should be unbusied
* because it's always called before the completion. This function is
* for a requeue after completion, which should only occur in this
* file.
*/
static int __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)
{
struct Scsi_Host *host = cmd->device->host;
struct scsi_device *device = cmd->device;
struct scsi_target *starget = scsi_target(device);
struct request_queue *q = device->request_queue;
unsigned long flags;
SCSI_LOG_MLQUEUE(1,
printk("Inserting command %p into mlqueue\n", cmd));
/*
* Set the appropriate busy bit for the device/host.
*
* If the host/device isn't busy, assume that something actually
* completed, and that we should be able to queue a command now.
*
* Note that the prior mid-layer assumption that any host could
* always queue at least one command is now broken. The mid-layer
* will implement a user specifiable stall (see
* scsi_host.max_host_blocked and scsi_device.max_device_blocked)
* if a command is requeued with no other commands outstanding
* either for the device or for the host.
*/
switch (reason) {
case SCSI_MLQUEUE_HOST_BUSY:
host->host_blocked = host->max_host_blocked;
break;
case SCSI_MLQUEUE_DEVICE_BUSY:
case SCSI_MLQUEUE_EH_RETRY:
device->device_blocked = device->max_device_blocked;
break;
case SCSI_MLQUEUE_TARGET_BUSY:
starget->target_blocked = starget->max_target_blocked;
break;
}
/*
* Decrement the counters, since these commands are no longer
* active on the host/device.
*/
if (unbusy)
scsi_device_unbusy(device);
/*
* Requeue this command. It will go before all other commands
* that are already in the queue.
*/
spin_lock_irqsave(q->queue_lock, flags);
blk_requeue_request(q, cmd->request);
spin_unlock_irqrestore(q->queue_lock, flags);
kblockd_schedule_work(q, &device->requeue_work);
return 0;
}
/*
* Function: scsi_queue_insert()
*
* Purpose: Insert a command in the midlevel queue.
*
* Arguments: cmd - command that we are adding to queue.
* reason - why we are inserting command to queue.
*
* Lock status: Assumed that lock is not held upon entry.
*
* Returns: Nothing.
*
* Notes: We do this for one of two cases. Either the host is busy
* and it cannot accept any more commands for the time being,
* or the device returned QUEUE_FULL and can accept no more
* commands.
* Notes: This could be called either from an interrupt context or a
* normal process context.
*/
int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
{
return __scsi_queue_insert(cmd, reason, 1);
}
/**
* scsi_execute - insert request and wait for the result
* @sdev: scsi device
* @cmd: scsi command
* @data_direction: data direction
* @buffer: data buffer
* @bufflen: len of buffer
* @sense: optional sense buffer
* @timeout: request timeout in seconds
* @retries: number of times to retry request
* @flags: or into request flags;
* @resid: optional residual length
*
* returns the req->errors value which is the scsi_cmnd result
* field.
*/
int scsi_execute(struct scsi_device *sdev, const unsigned char *cmd,
int data_direction, void *buffer, unsigned bufflen,
unsigned char *sense, int timeout, int retries, int flags,
int *resid)
{
struct request *req;
int write = (data_direction == DMA_TO_DEVICE);
int ret = DRIVER_ERROR << 24;
req = blk_get_request(sdev->request_queue, write, __GFP_WAIT);
if (!req)
return ret;
if (bufflen && blk_rq_map_kern(sdev->request_queue, req,
buffer, bufflen, __GFP_WAIT))
goto out;
req->cmd_len = COMMAND_SIZE(cmd[0]);
memcpy(req->cmd, cmd, req->cmd_len);
req->sense = sense;
req->sense_len = 0;
req->retries = retries;
req->timeout = timeout;
req->cmd_type = REQ_TYPE_BLOCK_PC;
req->cmd_flags |= flags | REQ_QUIET | REQ_PREEMPT;
/*
* head injection *required* here otherwise quiesce won't work
*/
blk_execute_rq(req->q, NULL, req, 1);
/*
* Some devices (USB mass-storage in particular) may transfer
* garbage data together with a residue indicating that the data
* is invalid. Prevent the garbage from being misinterpreted
* and prevent security leaks by zeroing out the excess data.
*/
if (unlikely(req->resid_len > 0 && req->resid_len <= bufflen))
memset(buffer + (bufflen - req->resid_len), 0, req->resid_len);
if (resid)
*resid = req->resid_len;
ret = req->errors;
out:
blk_put_request(req);
return ret;
}
EXPORT_SYMBOL(scsi_execute);
int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
int data_direction, void *buffer, unsigned bufflen,
struct scsi_sense_hdr *sshdr, int timeout, int retries,
int *resid)
{
char *sense = NULL;
int result;
if (sshdr) {
sense = kzalloc(SCSI_SENSE_BUFFERSIZE, GFP_NOIO);
if (!sense)
return DRIVER_ERROR << 24;
}
result = scsi_execute(sdev, cmd, data_direction, buffer, bufflen,
sense, timeout, retries, 0, resid);
if (sshdr)
scsi_normalize_sense(sense, SCSI_SENSE_BUFFERSIZE, sshdr);
kfree(sense);
return result;
}
EXPORT_SYMBOL(scsi_execute_req);
/*
* Function: scsi_init_cmd_errh()
*
* Purpose: Initialize cmd fields related to error handling.
*
* Arguments: cmd - command that is ready to be queued.
*
* Notes: This function has the job of initializing a number of
* fields related to error handling. Typically this will
* be called once for each command, as required.
*/
static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
{
cmd->serial_number = 0;
scsi_set_resid(cmd, 0);
memset(cmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
if (cmd->cmd_len == 0)
cmd->cmd_len = scsi_command_size(cmd->cmnd);
}
void scsi_device_unbusy(struct scsi_device *sdev)
{
struct Scsi_Host *shost = sdev->host;
struct scsi_target *starget = scsi_target(sdev);
unsigned long flags;
spin_lock_irqsave(shost->host_lock, flags);
shost->host_busy--;
starget->target_busy--;
if (unlikely(scsi_host_in_recovery(shost) &&
(shost->host_failed || shost->host_eh_scheduled)))
scsi_eh_wakeup(shost);
spin_unlock(shost->host_lock);
spin_lock(sdev->request_queue->queue_lock);
sdev->device_busy--;
spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
}
/*
* Called for single_lun devices on IO completion. Clear starget_sdev_user,
* and call blk_run_queue for all the scsi_devices on the target -
* including current_sdev first.
*
* Called with *no* scsi locks held.
*/
static void scsi_single_lun_run(struct scsi_device *current_sdev)
{
struct Scsi_Host *shost = current_sdev->host;
struct scsi_device *sdev, *tmp;
struct scsi_target *starget = scsi_target(current_sdev);
unsigned long flags;
spin_lock_irqsave(shost->host_lock, flags);
starget->starget_sdev_user = NULL;
spin_unlock_irqrestore(shost->host_lock, flags);
/*
* Call blk_run_queue for all LUNs on the target, starting with
* current_sdev. We race with others (to set starget_sdev_user),
* but in most cases, we will be first. Ideally, each LU on the
* target would get some limited time or requests on the target.
*/
blk_run_queue(current_sdev->request_queue);
spin_lock_irqsave(shost->host_lock, flags);
if (starget->starget_sdev_user)
goto out;
list_for_each_entry_safe(sdev, tmp, &starget->devices,
same_target_siblings) {
if (sdev == current_sdev)
continue;
if (scsi_device_get(sdev))
continue;
spin_unlock_irqrestore(shost->host_lock, flags);
blk_run_queue(sdev->request_queue);
spin_lock_irqsave(shost->host_lock, flags);
scsi_device_put(sdev);
}
out:
spin_unlock_irqrestore(shost->host_lock, flags);
}
static inline int scsi_device_is_busy(struct scsi_device *sdev)
{
if (sdev->device_busy >= sdev->queue_depth || sdev->device_blocked)
return 1;
return 0;
}
static inline int scsi_target_is_busy(struct scsi_target *starget)
{
return ((starget->can_queue > 0 &&
starget->target_busy >= starget->can_queue) ||
starget->target_blocked);
}
static inline int scsi_host_is_busy(struct Scsi_Host *shost)
{
if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
shost->host_blocked || shost->host_self_blocked)
return 1;
return 0;
}
/*
* Function: scsi_run_queue()
*
* Purpose: Select a proper request queue to serve next
*
* Arguments: q - last request's queue
*
* Returns: Nothing
*
* Notes: The previous command was completely finished, start
* a new one if possible.
*/
static void scsi_run_queue(struct request_queue *q)
{
struct scsi_device *sdev = q->queuedata;
struct Scsi_Host *shost;
LIST_HEAD(starved_list);
unsigned long flags;
/* if the device is dead, sdev will be NULL, so no queue to run */
if (!sdev)
return;
shost = sdev->host;
if (scsi_target(sdev)->single_lun)
scsi_single_lun_run(sdev);
spin_lock_irqsave(shost->host_lock, flags);
list_splice_init(&shost->starved_list, &starved_list);
while (!list_empty(&starved_list)) {
/*
* As long as shost is accepting commands and we have
* starved queues, call blk_run_queue. scsi_request_fn
* drops the queue_lock and can add us back to the
* starved_list.
*
* host_lock protects the starved_list and starved_entry.
* scsi_request_fn must get the host_lock before checking
* or modifying starved_list or starved_entry.
*/
if (scsi_host_is_busy(shost))
break;
sdev = list_entry(starved_list.next,
struct scsi_device, starved_entry);
list_del_init(&sdev->starved_entry);
if (scsi_target_is_busy(scsi_target(sdev))) {
list_move_tail(&sdev->starved_entry,
&shost->starved_list);
continue;
}
spin_unlock(shost->host_lock);
spin_lock(sdev->request_queue->queue_lock);
__blk_run_queue(sdev->request_queue);
spin_unlock(sdev->request_queue->queue_lock);
spin_lock(shost->host_lock);
}
/* put any unprocessed entries back */
list_splice(&starved_list, &shost->starved_list);
spin_unlock_irqrestore(shost->host_lock, flags);
blk_run_queue(q);
}
void scsi_requeue_run_queue(struct work_struct *work)
{
struct scsi_device *sdev;
struct request_queue *q;
sdev = container_of(work, struct scsi_device, requeue_work);
q = sdev->request_queue;
scsi_run_queue(q);
}
/*
* Function: scsi_requeue_command()
*
* Purpose: Handle post-processing of completed commands.
*
* Arguments: q - queue to operate on
* cmd - command that may need to be requeued.
*
* Returns: Nothing
*
* Notes: After command completion, there may be blocks left
* over which weren't finished by the previous command
* this can be for a number of reasons - the main one is
* I/O errors in the middle of the request, in which case
* we need to request the blocks that come after the bad
* sector.
* Notes: Upon return, cmd is a stale pointer.
*/
static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
{
struct request *req = cmd->request;
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
scsi_unprep_request(req);
blk_requeue_request(q, req);
spin_unlock_irqrestore(q->queue_lock, flags);
scsi_run_queue(q);
}
void scsi_next_command(struct scsi_cmnd *cmd)
{
struct scsi_device *sdev = cmd->device;
struct request_queue *q = sdev->request_queue;
/* need to hold a reference on the device before we let go of the cmd */
get_device(&sdev->sdev_gendev);
scsi_put_command(cmd);
scsi_run_queue(q);
/* ok to remove device now */
put_device(&sdev->sdev_gendev);
}
void scsi_run_host_queues(struct Scsi_Host *shost)
{
struct scsi_device *sdev;
shost_for_each_device(sdev, shost)
scsi_run_queue(sdev->request_queue);
}
static void __scsi_release_buffers(struct scsi_cmnd *, int);
/*
* Function: scsi_end_request()
*
* Purpose: Post-processing of completed commands (usually invoked at end
* of upper level post-processing and scsi_io_completion).
*
* Arguments: cmd - command that is complete.
* error - 0 if I/O indicates success, < 0 for I/O error.
* bytes - number of bytes of completed I/O
* requeue - indicates whether we should requeue leftovers.
*
* Lock status: Assumed that lock is not held upon entry.
*
* Returns: cmd if requeue required, NULL otherwise.
*
* Notes: This is called for block device requests in order to
* mark some number of sectors as complete.
*
* We are guaranteeing that the request queue will be goosed
* at some point during this call.
* Notes: If cmd was requeued, upon return it will be a stale pointer.
*/
static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
int bytes, int requeue)
{
struct request_queue *q = cmd->device->request_queue;
struct request *req = cmd->request;
/*
* If there are blocks left over at the end, set up the command
* to queue the remainder of them.
*/
if (blk_end_request(req, error, bytes)) {
/* kill remainder if no retrys */
if (error && scsi_noretry_cmd(cmd))
blk_end_request_all(req, error);
else {
if (requeue) {
/*
* Bleah. Leftovers again. Stick the
* leftovers in the front of the
* queue, and goose the queue again.
*/
scsi_release_buffers(cmd);
scsi_requeue_command(q, cmd);
cmd = NULL;
}
return cmd;
}
}
/*
* This will goose the queue request function at the end, so we don't
* need to worry about launching another command.
*/
__scsi_release_buffers(cmd, 0);
scsi_next_command(cmd);
return NULL;
}
static inline unsigned int scsi_sgtable_index(unsigned short nents)
{
unsigned int index;
BUG_ON(nents > SCSI_MAX_SG_SEGMENTS);
if (nents <= 8)
index = 0;
else
index = get_count_order(nents) - 3;
return index;
}
static void scsi_sg_free(struct scatterlist *sgl, unsigned int nents)
{
struct scsi_host_sg_pool *sgp;
sgp = scsi_sg_pools + scsi_sgtable_index(nents);
mempool_free(sgl, sgp->pool);
}
static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
{
struct scsi_host_sg_pool *sgp;
sgp = scsi_sg_pools + scsi_sgtable_index(nents);
return mempool_alloc(sgp->pool, gfp_mask);
}
static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents,
gfp_t gfp_mask)
{
int ret;
BUG_ON(!nents);
ret = __sg_alloc_table(&sdb->table, nents, SCSI_MAX_SG_SEGMENTS,
gfp_mask, scsi_sg_alloc);
if (unlikely(ret))
__sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS,
scsi_sg_free);
return ret;
}
static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
{
__sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
}
static void __scsi_release_buffers(struct scsi_cmnd *cmd, int do_bidi_check)
{
if (cmd->sdb.table.nents)
scsi_free_sgtable(&cmd->sdb);
memset(&cmd->sdb, 0, sizeof(cmd->sdb));
if (do_bidi_check && scsi_bidi_cmnd(cmd)) {
struct scsi_data_buffer *bidi_sdb =
cmd->request->next_rq->special;
scsi_free_sgtable(bidi_sdb);
kmem_cache_free(scsi_sdb_cache, bidi_sdb);
cmd->request->next_rq->special = NULL;
}
if (scsi_prot_sg_count(cmd))
scsi_free_sgtable(cmd->prot_sdb);
}
/*
* Function: scsi_release_buffers()
*
* Purpose: Completion processing for block device I/O requests.
*
* Arguments: cmd - command that we are bailing.
*
* Lock status: Assumed that no lock is held upon entry.
*
* Returns: Nothing
*
* Notes: In the event that an upper level driver rejects a
* command, we must release resources allocated during
* the __init_io() function. Primarily this would involve
* the scatter-gather table, and potentially any bounce
* buffers.
*/
void scsi_release_buffers(struct scsi_cmnd *cmd)
{
__scsi_release_buffers(cmd, 1);
}
EXPORT_SYMBOL(scsi_release_buffers);
static int __scsi_error_from_host_byte(struct scsi_cmnd *cmd, int result)
{
int error = 0;
switch(host_byte(result)) {
case DID_TRANSPORT_FAILFAST:
error = -ENOLINK;
break;
case DID_TARGET_FAILURE:
set_host_byte(cmd, DID_OK);
error = -EREMOTEIO;
break;
case DID_NEXUS_FAILURE:
set_host_byte(cmd, DID_OK);
error = -EBADE;
break;
default:
error = -EIO;
break;
}
return error;
}
/*
* Function: scsi_io_completion()
*
* Purpose: Completion processing for block device I/O requests.
*
* Arguments: cmd - command that is finished.
*
* Lock status: Assumed that no lock is held upon entry.
*
* Returns: Nothing
*
* Notes: This function is matched in terms of capabilities to
* the function that created the scatter-gather list.
* In other words, if there are no bounce buffers
* (the normal case for most drivers), we don't need
* the logic to deal with cleaning up afterwards.
*
* We must call scsi_end_request(). This will finish off
* the specified number of sectors. If we are done, the
* command block will be released and the queue function
* will be goosed. If we are not done then we have to
* figure out what to do next:
*
* a) We can call scsi_requeue_command(). The request
* will be unprepared and put back on the queue. Then
* a new command will be created for it. This should
* be used if we made forward progress, or if we want
* to switch from READ(10) to READ(6) for example.
*
* b) We can call scsi_queue_insert(). The request will
* be put back on the queue and retried using the same
* command as before, possibly after a delay.
*
* c) We can call blk_end_request() with -EIO to fail
* the remainder of the request.
*/
void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
{
int result = cmd->result;
struct request_queue *q = cmd->device->request_queue;
struct request *req = cmd->request;
int error = 0;
struct scsi_sense_hdr sshdr;
int sense_valid = 0;
int sense_deferred = 0;
enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
ACTION_DELAYED_RETRY} action;
char *description = NULL;
if (result) {
sense_valid = scsi_command_normalize_sense(cmd, &sshdr);
if (sense_valid)
sense_deferred = scsi_sense_is_deferred(&sshdr);
}
if (req->cmd_type == REQ_TYPE_BLOCK_PC) { /* SG_IO ioctl from block level */
req->errors = result;
if (result) {
if (sense_valid && req->sense) {
/*
* SG_IO wants current and deferred errors
*/
int len = 8 + cmd->sense_buffer[7];
if (len > SCSI_SENSE_BUFFERSIZE)
len = SCSI_SENSE_BUFFERSIZE;
memcpy(req->sense, cmd->sense_buffer, len);
req->sense_len = len;
}
if (!sense_deferred)
error = __scsi_error_from_host_byte(cmd, result);
}
req->resid_len = scsi_get_resid(cmd);
if (scsi_bidi_cmnd(cmd)) {
/*
* Bidi commands Must be complete as a whole,
* both sides at once.
*/
req->next_rq->resid_len = scsi_in(cmd)->resid;
scsi_release_buffers(cmd);
blk_end_request_all(req, 0);
scsi_next_command(cmd);
return;
}
}
/* no bidi support for !REQ_TYPE_BLOCK_PC yet */
BUG_ON(blk_bidi_rq(req));
/*
* Next deal with any sectors which we were able to correctly
* handle.
*/
SCSI_LOG_HLCOMPLETE(1, printk("%u sectors total, "
"%d bytes done.\n",
blk_rq_sectors(req), good_bytes));
/*
* Recovered errors need reporting, but they're always treated
* as success, so fiddle the result code here. For BLOCK_PC
* we already took a copy of the original into rq->errors which
* is what gets returned to the user
*/
if (sense_valid && (sshdr.sense_key == RECOVERED_ERROR)) {
/* if ATA PASS-THROUGH INFORMATION AVAILABLE skip
* print since caller wants ATA registers. Only occurs on
* SCSI ATA PASS_THROUGH commands when CK_COND=1
*/
if ((sshdr.asc == 0x0) && (sshdr.ascq == 0x1d))
;
else if (!(req->cmd_flags & REQ_QUIET))
scsi_print_sense("", cmd);
result = 0;
/* BLOCK_PC may have set error */
error = 0;
}
/*
* A number of bytes were successfully read. If there
* are leftovers and there is some kind of error
* (result != 0), retry the rest.
*/
if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
return;
error = __scsi_error_from_host_byte(cmd, result);
if (host_byte(result) == DID_RESET) {
/* Third party bus reset or reset for error recovery
* reasons. Just retry the command and see what
* happens.
*/
action = ACTION_RETRY;
} else if (sense_valid && !sense_deferred) {
switch (sshdr.sense_key) {
case UNIT_ATTENTION:
if (cmd->device->removable) {
/* Detected disc change. Set a bit
* and quietly refuse further access.
*/
cmd->device->changed = 1;
description = "Media Changed";
action = ACTION_FAIL;
} else {
/* Must have been a power glitch, or a
* bus reset. Could not have been a
* media change, so we just retry the
* command and see what happens.
*/
action = ACTION_RETRY;
}
break;
case ILLEGAL_REQUEST:
/* If we had an ILLEGAL REQUEST returned, then
* we may have performed an unsupported
* command. The only thing this should be
* would be a ten byte read where only a six
* byte read was supported. Also, on a system
* where READ CAPACITY failed, we may have
* read past the end of the disk.
*/
if ((cmd->device->use_10_for_rw &&
sshdr.asc == 0x20 && sshdr.ascq == 0x00) &&
(cmd->cmnd[0] == READ_10 ||
cmd->cmnd[0] == WRITE_10)) {
/* This will issue a new 6-byte command. */
cmd->device->use_10_for_rw = 0;
action = ACTION_REPREP;
} else if (sshdr.asc == 0x10) /* DIX */ {
description = "Host Data Integrity Failure";
action = ACTION_FAIL;
error = -EILSEQ;
/* INVALID COMMAND OPCODE or INVALID FIELD IN CDB */
} else if ((sshdr.asc == 0x20 || sshdr.asc == 0x24) &&
(cmd->cmnd[0] == UNMAP ||
cmd->cmnd[0] == WRITE_SAME_16 ||
cmd->cmnd[0] == WRITE_SAME)) {
description = "Discard failure";
action = ACTION_FAIL;
error = -EREMOTEIO;
} else
action = ACTION_FAIL;
break;
case ABORTED_COMMAND:
action = ACTION_FAIL;
if (sshdr.asc == 0x10) { /* DIF */
description = "Target Data Integrity Failure";
error = -EILSEQ;
}
break;
case NOT_READY:
/* If the device is in the process of becoming
* ready, or has a temporary blockage, retry.
*/
if (sshdr.asc == 0x04) {
switch (sshdr.ascq) {
case 0x01: /* becoming ready */
case 0x04: /* format in progress */
case 0x05: /* rebuild in progress */
case 0x06: /* recalculation in progress */
case 0x07: /* operation in progress */
case 0x08: /* Long write in progress */
case 0x09: /* self test in progress */
case 0x14: /* space allocation in progress */
action = ACTION_DELAYED_RETRY;
break;
default:
description = "Device not ready";
action = ACTION_FAIL;
break;
}
} else {
description = "Device not ready";
action = ACTION_FAIL;
}
break;
case VOLUME_OVERFLOW:
/* See SSC3rXX or current. */
action = ACTION_FAIL;
break;
default:
description = "Unhandled sense code";
action = ACTION_FAIL;
break;
}
} else {
description = "Unhandled error code";
action = ACTION_FAIL;
}
switch (action) {
case ACTION_FAIL:
/* Give up and fail the remainder of the request */
scsi_release_buffers(cmd);
if (!(req->cmd_flags & REQ_QUIET)) {
if (description)
scmd_printk(KERN_INFO, cmd, "%s\n",
description);
scsi_print_result(cmd);
if (driver_byte(result) & DRIVER_SENSE)
scsi_print_sense("", cmd);
scsi_print_command(cmd);
}
if (blk_end_request_err(req, error))
scsi_requeue_command(q, cmd);
else
scsi_next_command(cmd);
break;
case ACTION_REPREP:
/* Unprep the request and put it back at the head of the queue.
* A new command will be prepared and issued.
*/
scsi_release_buffers(cmd);
scsi_requeue_command(q, cmd);
break;
case ACTION_RETRY:
/* Retry the same command immediately */
__scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY, 0);
break;
case ACTION_DELAYED_RETRY:
/* Retry the same command after a delay */
__scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, 0);
break;
}
}
static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
gfp_t gfp_mask)
{
int count;
/*
* If sg table allocation fails, requeue request later.
*/
if (unlikely(scsi_alloc_sgtable(sdb, req->nr_phys_segments,
gfp_mask))) {
return BLKPREP_DEFER;
}
req->buffer = NULL;
/*
* Next, walk the list, and fill in the addresses and sizes of
* each segment.
*/
count = blk_rq_map_sg(req->q, req, sdb->table.sgl);
BUG_ON(count > sdb->table.nents);
sdb->table.nents = count;
sdb->length = blk_rq_bytes(req);
return BLKPREP_OK;
}
/*
* Function: scsi_init_io()
*
* Purpose: SCSI I/O initialize function.
*
* Arguments: cmd - Command descriptor we wish to initialize
*
* Returns: 0 on success
* BLKPREP_DEFER if the failure is retryable
* BLKPREP_KILL if the failure is fatal
*/
int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
{
struct request *rq = cmd->request;
int error = scsi_init_sgtable(rq, &cmd->sdb, gfp_mask);
if (error)
goto err_exit;
if (blk_bidi_rq(rq)) {
struct scsi_data_buffer *bidi_sdb = kmem_cache_zalloc(
scsi_sdb_cache, GFP_ATOMIC);
if (!bidi_sdb) {
error = BLKPREP_DEFER;
goto err_exit;
}
rq->next_rq->special = bidi_sdb;
error = scsi_init_sgtable(rq->next_rq, bidi_sdb, GFP_ATOMIC);
if (error)
goto err_exit;
}
if (blk_integrity_rq(rq)) {
struct scsi_data_buffer *prot_sdb = cmd->prot_sdb;
int ivecs, count;
BUG_ON(prot_sdb == NULL);
ivecs = blk_rq_count_integrity_sg(rq->q, rq->bio);
if (scsi_alloc_sgtable(prot_sdb, ivecs, gfp_mask)) {
error = BLKPREP_DEFER;
goto err_exit;
}
count = blk_rq_map_integrity_sg(rq->q, rq->bio,
prot_sdb->table.sgl);
BUG_ON(unlikely(count > ivecs));
BUG_ON(unlikely(count > queue_max_integrity_segments(rq->q)));
cmd->prot_sdb = prot_sdb;
cmd->prot_sdb->table.nents = count;
}
return BLKPREP_OK ;
err_exit:
scsi_release_buffers(cmd);
cmd->request->special = NULL;
scsi_put_command(cmd);
return error;
}
EXPORT_SYMBOL(scsi_init_io);
static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
struct request *req)
{
struct scsi_cmnd *cmd;
if (!req->special) {
cmd = scsi_get_command(sdev, GFP_ATOMIC);
if (unlikely(!cmd))
return NULL;
req->special = cmd;
} else {
cmd = req->special;
}
/* pull a tag out of the request if we have one */
cmd->tag = req->tag;
cmd->request = req;
cmd->cmnd = req->cmd;
cmd->prot_op = SCSI_PROT_NORMAL;
return cmd;
}
int scsi_setup_blk_pc_cmnd(struct scsi_device *sdev, struct request *req)
{
struct scsi_cmnd *cmd;
int ret = scsi_prep_state_check(sdev, req);
if (ret != BLKPREP_OK)
return ret;
cmd = scsi_get_cmd_from_req(sdev, req);
if (unlikely(!cmd))
return BLKPREP_DEFER;
/*
* BLOCK_PC requests may transfer data, in which case they must
* a bio attached to them. Or they might contain a SCSI command
* that does not transfer data, in which case they may optionally
* submit a request without an attached bio.
*/
if (req->bio) {
int ret;
BUG_ON(!req->nr_phys_segments);
ret = scsi_init_io(cmd, GFP_ATOMIC);
if (unlikely(ret))
return ret;
} else {
BUG_ON(blk_rq_bytes(req));
memset(&cmd->sdb, 0, sizeof(cmd->sdb));
req->buffer = NULL;
}
cmd->cmd_len = req->cmd_len;
if (!blk_rq_bytes(req))
cmd->sc_data_direction = DMA_NONE;
else if (rq_data_dir(req) == WRITE)
cmd->sc_data_direction = DMA_TO_DEVICE;
else
cmd->sc_data_direction = DMA_FROM_DEVICE;
cmd->transfersize = blk_rq_bytes(req);
cmd->allowed = req->retries;
return BLKPREP_OK;
}
EXPORT_SYMBOL(scsi_setup_blk_pc_cmnd);
/*
* Setup a REQ_TYPE_FS command. These are simple read/write request
* from filesystems that still need to be translated to SCSI CDBs from
* the ULD.
*/
int scsi_setup_fs_cmnd(struct scsi_device *sdev, struct request *req)
{
struct scsi_cmnd *cmd;
int ret = scsi_prep_state_check(sdev, req);
if (ret != BLKPREP_OK)
return ret;
if (unlikely(sdev->scsi_dh_data && sdev->scsi_dh_data->scsi_dh
&& sdev->scsi_dh_data->scsi_dh->prep_fn)) {
ret = sdev->scsi_dh_data->scsi_dh->prep_fn(sdev, req);
if (ret != BLKPREP_OK)
return ret;
}
/*
* Filesystem requests must transfer data.
*/
BUG_ON(!req->nr_phys_segments);
cmd = scsi_get_cmd_from_req(sdev, req);
if (unlikely(!cmd))
return BLKPREP_DEFER;
memset(cmd->cmnd, 0, BLK_MAX_CDB);
return scsi_init_io(cmd, GFP_ATOMIC);
}
EXPORT_SYMBOL(scsi_setup_fs_cmnd);
int scsi_prep_state_check(struct scsi_device *sdev, struct request *req)
{
int ret = BLKPREP_OK;
/*
* If the device is not in running state we will reject some
* or all commands.
*/
if (unlikely(sdev->sdev_state != SDEV_RUNNING)) {
switch (sdev->sdev_state) {
case SDEV_OFFLINE:
/*
* If the device is offline we refuse to process any
* commands. The device must be brought online
* before trying any recovery commands.
*/
sdev_printk(KERN_ERR, sdev,
"rejecting I/O to offline device\n");
ret = BLKPREP_KILL;
break;
case SDEV_DEL:
/*
* If the device is fully deleted, we refuse to
* process any commands as well.
*/
sdev_printk(KERN_ERR, sdev,
"rejecting I/O to dead device\n");
ret = BLKPREP_KILL;
break;
case SDEV_QUIESCE:
case SDEV_BLOCK:
case SDEV_CREATED_BLOCK:
/*
* If the devices is blocked we defer normal commands.
*/
if (!(req->cmd_flags & REQ_PREEMPT))
ret = BLKPREP_DEFER;
break;
default:
/*
* For any other not fully online state we only allow
* special commands. In particular any user initiated
* command is not allowed.
*/
if (!(req->cmd_flags & REQ_PREEMPT))
ret = BLKPREP_KILL;
break;
}
}
return ret;
}
EXPORT_SYMBOL(scsi_prep_state_check);
int scsi_prep_return(struct request_queue *q, struct request *req, int ret)
{
struct scsi_device *sdev = q->queuedata;
switch (ret) {
case BLKPREP_KILL:
req->errors = DID_NO_CONNECT << 16;
/* release the command and kill it */
if (req->special) {
struct scsi_cmnd *cmd = req->special;
scsi_release_buffers(cmd);
scsi_put_command(cmd);
req->special = NULL;
}
break;
case BLKPREP_DEFER:
/*
* If we defer, the blk_peek_request() returns NULL, but the
* queue must be restarted, so we schedule a callback to happen
* shortly.
*/
if (sdev->device_busy == 0)
blk_delay_queue(q, SCSI_QUEUE_DELAY);
break;
default:
req->cmd_flags |= REQ_DONTPREP;
}
return ret;
}
EXPORT_SYMBOL(scsi_prep_return);
int scsi_prep_fn(struct request_queue *q, struct request *req)
{
struct scsi_device *sdev = q->queuedata;
int ret = BLKPREP_KILL;
if (req->cmd_type == REQ_TYPE_BLOCK_PC)
ret = scsi_setup_blk_pc_cmnd(sdev, req);
return scsi_prep_return(q, req, ret);
}
EXPORT_SYMBOL(scsi_prep_fn);
/*
* scsi_dev_queue_ready: if we can send requests to sdev, return 1 else
* return 0.
*
* Called with the queue_lock held.
*/
static inline int scsi_dev_queue_ready(struct request_queue *q,
struct scsi_device *sdev)
{
if (sdev->device_busy == 0 && sdev->device_blocked) {
/*
* unblock after device_blocked iterates to zero
*/
if (--sdev->device_blocked == 0) {
SCSI_LOG_MLQUEUE(3,
sdev_printk(KERN_INFO, sdev,
"unblocking device at zero depth\n"));
} else {
blk_delay_queue(q, SCSI_QUEUE_DELAY);
return 0;
}
}
if (scsi_device_is_busy(sdev))
return 0;
return 1;
}
/*
* scsi_target_queue_ready: checks if there we can send commands to target
* @sdev: scsi device on starget to check.
*
* Called with the host lock held.
*/
static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
struct scsi_device *sdev)
{
struct scsi_target *starget = scsi_target(sdev);
if (starget->single_lun) {
if (starget->starget_sdev_user &&
starget->starget_sdev_user != sdev)
return 0;
starget->starget_sdev_user = sdev;
}
if (starget->target_busy == 0 && starget->target_blocked) {
/*
* unblock after target_blocked iterates to zero
*/
if (--starget->target_blocked == 0) {
SCSI_LOG_MLQUEUE(3, starget_printk(KERN_INFO, starget,
"unblocking target at zero depth\n"));
} else
return 0;
}
if (scsi_target_is_busy(starget)) {
list_move_tail(&sdev->starved_entry, &shost->starved_list);
return 0;
}
return 1;
}
/*
* scsi_host_queue_ready: if we can send requests to shost, return 1 else
* return 0. We must end up running the queue again whenever 0 is
* returned, else IO can hang.
*
* Called with host_lock held.
*/
static inline int scsi_host_queue_ready(struct request_queue *q,
struct Scsi_Host *shost,
struct scsi_device *sdev)
{
if (scsi_host_in_recovery(shost))
return 0;
if (shost->host_busy == 0 && shost->host_blocked) {
/*
* unblock after host_blocked iterates to zero
*/
if (--shost->host_blocked == 0) {
SCSI_LOG_MLQUEUE(3,
printk("scsi%d unblocking host at zero depth\n",
shost->host_no));
} else {
return 0;
}
}
if (scsi_host_is_busy(shost)) {
if (list_empty(&sdev->starved_entry))
list_add_tail(&sdev->starved_entry, &shost->starved_list);
return 0;
}
/* We're OK to process the command, so we can't be starved */
if (!list_empty(&sdev->starved_entry))
list_del_init(&sdev->starved_entry);
return 1;
}
/*
* Busy state exporting function for request stacking drivers.
*
* For efficiency, no lock is taken to check the busy state of
* shost/starget/sdev, since the returned value is not guaranteed and
* may be changed after request stacking drivers call the function,
* regardless of taking lock or not.
*
* When scsi can't dispatch I/Os anymore and needs to kill I/Os
* (e.g. !sdev), scsi needs to return 'not busy'.
* Otherwise, request stacking drivers may hold requests forever.
*/
static int scsi_lld_busy(struct request_queue *q)
{
struct scsi_device *sdev = q->queuedata;
struct Scsi_Host *shost;
if (!sdev)
return 0;
shost = sdev->host;
/*
* Ignore host/starget busy state.
* Since block layer does not have a concept of fairness across
* multiple queues, congestion of host/starget needs to be handled
* in SCSI layer.
*/
if (scsi_host_in_recovery(shost) || scsi_device_is_busy(sdev))
return 1;
return 0;
}
/*
* Kill a request for a dead device
*/
static void scsi_kill_request(struct request *req, struct request_queue *q)
{
struct scsi_cmnd *cmd = req->special;
struct scsi_device *sdev;
struct scsi_target *starget;
struct Scsi_Host *shost;
blk_start_request(req);
scmd_printk(KERN_INFO, cmd, "killing request\n");
sdev = cmd->device;
starget = scsi_target(sdev);
shost = sdev->host;
scsi_init_cmd_errh(cmd);
cmd->result = DID_NO_CONNECT << 16;
atomic_inc(&cmd->device->iorequest_cnt);
/*
* SCSI request completion path will do scsi_device_unbusy(),
* bump busy counts. To bump the counters, we need to dance
* with the locks as normal issue path does.
*/
sdev->device_busy++;
spin_unlock(sdev->request_queue->queue_lock);
spin_lock(shost->host_lock);
shost->host_busy++;
starget->target_busy++;
spin_unlock(shost->host_lock);
spin_lock(sdev->request_queue->queue_lock);
blk_complete_request(req);
}
static void scsi_softirq_done(struct request *rq)
{
struct scsi_cmnd *cmd = rq->special;
unsigned long wait_for = (cmd->allowed + 1) * rq->timeout;
int disposition;
INIT_LIST_HEAD(&cmd->eh_entry);
atomic_inc(&cmd->device->iodone_cnt);
if (cmd->result)
atomic_inc(&cmd->device->ioerr_cnt);
disposition = scsi_decide_disposition(cmd);
if (disposition != SUCCESS &&
time_before(cmd->jiffies_at_alloc + wait_for, jiffies)) {
sdev_printk(KERN_ERR, cmd->device,
"timing out command, waited %lus\n",
wait_for/HZ);
disposition = SUCCESS;
}
scsi_log_completion(cmd, disposition);
switch (disposition) {
case SUCCESS:
scsi_finish_command(cmd);
break;
case NEEDS_RETRY:
scsi_queue_insert(cmd, SCSI_MLQUEUE_EH_RETRY);
break;
case ADD_TO_MLQUEUE:
scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
break;
default:
if (!scsi_eh_scmd_add(cmd, 0))
scsi_finish_command(cmd);
}
}
/*
* Function: scsi_request_fn()
*
* Purpose: Main strategy routine for SCSI.
*
* Arguments: q - Pointer to actual queue.
*
* Returns: Nothing
*
* Lock status: IO request lock assumed to be held when called.
*/
static void scsi_request_fn(struct request_queue *q)
{
struct scsi_device *sdev = q->queuedata;
struct Scsi_Host *shost;
struct scsi_cmnd *cmd;
struct request *req;
if (!sdev) {
while ((req = blk_peek_request(q)) != NULL)
scsi_kill_request(req, q);
return;
}
if(!get_device(&sdev->sdev_gendev))
/* We must be tearing the block queue down already */
return;
/*
* To start with, we keep looping until the queue is empty, or until
* the host is no longer able to accept any more requests.
*/
shost = sdev->host;
for (;;) {
int rtn;
/*
* get next queueable request. We do this early to make sure
* that the request is fully prepared even if we cannot
* accept it.
*/
req = blk_peek_request(q);
if (!req || !scsi_dev_queue_ready(q, sdev))
break;
if (unlikely(!scsi_device_online(sdev))) {
sdev_printk(KERN_ERR, sdev,
"rejecting I/O to offline device\n");
scsi_kill_request(req, q);
continue;
}
/*
* Remove the request from the request list.
*/
if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
blk_start_request(req);
sdev->device_busy++;
spin_unlock(q->queue_lock);
cmd = req->special;
if (unlikely(cmd == NULL)) {
printk(KERN_CRIT "impossible request in %s.\n"
"please mail a stack trace to "
"linux-scsi@vger.kernel.org\n",
__func__);
blk_dump_rq_flags(req, "foo");
BUG();
}
spin_lock(shost->host_lock);
/*
* We hit this when the driver is using a host wide
* tag map. For device level tag maps the queue_depth check
* in the device ready fn would prevent us from trying
* to allocate a tag. Since the map is a shared host resource
* we add the dev to the starved list so it eventually gets
* a run when a tag is freed.
*/
if (blk_queue_tagged(q) && !blk_rq_tagged(req)) {
if (list_empty(&sdev->starved_entry))
list_add_tail(&sdev->starved_entry,
&shost->starved_list);
goto not_ready;
}
if (!scsi_target_queue_ready(shost, sdev))
goto not_ready;
if (!scsi_host_queue_ready(q, shost, sdev))
goto not_ready;
scsi_target(sdev)->target_busy++;
shost->host_busy++;
/*
* XXX(hch): This is rather suboptimal, scsi_dispatch_cmd will
* take the lock again.
*/
spin_unlock_irq(shost->host_lock);
/*
* Finally, initialize any error handling parameters, and set up
* the timers for timeouts.
*/
scsi_init_cmd_errh(cmd);
/*
* Dispatch the command to the low-level driver.
*/
rtn = scsi_dispatch_cmd(cmd);
spin_lock_irq(q->queue_lock);
if (rtn)
goto out_delay;
}
goto out;
not_ready:
spin_unlock_irq(shost->host_lock);
/*
* lock q, handle tag, requeue req, and decrement device_busy. We
* must return with queue_lock held.
*
* Decrementing device_busy without checking it is OK, as all such
* cases (host limits or settings) should run the queue at some
* later time.
*/
spin_lock_irq(q->queue_lock);
blk_requeue_request(q, req);
sdev->device_busy--;
out_delay:
if (sdev->device_busy == 0)
blk_delay_queue(q, SCSI_QUEUE_DELAY);
out:
/* must be careful here...if we trigger the ->remove() function
* we cannot be holding the q lock */
spin_unlock_irq(q->queue_lock);
put_device(&sdev->sdev_gendev);
spin_lock_irq(q->queue_lock);
}
u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost)
{
struct device *host_dev;
u64 bounce_limit = 0xffffffff;
if (shost->unchecked_isa_dma)
return BLK_BOUNCE_ISA;
/*
* Platforms with virtual-DMA translation
* hardware have no practical limit.
*/
if (!PCI_DMA_BUS_IS_PHYS)
return BLK_BOUNCE_ANY;
host_dev = scsi_get_device(shost);
if (host_dev && host_dev->dma_mask)
bounce_limit = *host_dev->dma_mask;
return bounce_limit;
}
EXPORT_SYMBOL(scsi_calculate_bounce_limit);
struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost,
request_fn_proc *request_fn)
{
struct request_queue *q;
struct device *dev = shost->dma_dev;
q = blk_init_queue(request_fn, NULL);
if (!q)
return NULL;
/*
* this limit is imposed by hardware restrictions
*/
blk_queue_max_segments(q, min_t(unsigned short, shost->sg_tablesize,
SCSI_MAX_SG_CHAIN_SEGMENTS));
if (scsi_host_prot_dma(shost)) {
shost->sg_prot_tablesize =
min_not_zero(shost->sg_prot_tablesize,
(unsigned short)SCSI_MAX_PROT_SG_SEGMENTS);
BUG_ON(shost->sg_prot_tablesize < shost->sg_tablesize);
blk_queue_max_integrity_segments(q, shost->sg_prot_tablesize);
}
blk_queue_max_hw_sectors(q, shost->max_sectors);
blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
blk_queue_segment_boundary(q, shost->dma_boundary);
dma_set_seg_boundary(dev, shost->dma_boundary);
blk_queue_max_segment_size(q, dma_get_max_seg_size(dev));
if (!shost->use_clustering)
q->limits.cluster = 0;
/*
* set a reasonable default alignment on word boundaries: the
* host and device may alter it using
* blk_queue_update_dma_alignment() later.
*/
blk_queue_dma_alignment(q, 0x03);
return q;
}
EXPORT_SYMBOL(__scsi_alloc_queue);
struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
{
struct request_queue *q;
q = __scsi_alloc_queue(sdev->host, scsi_request_fn);
if (!q)
return NULL;
blk_queue_prep_rq(q, scsi_prep_fn);
blk_queue_softirq_done(q, scsi_softirq_done);
blk_queue_rq_timed_out(q, scsi_times_out);
blk_queue_lld_busy(q, scsi_lld_busy);
return q;
}
void scsi_free_queue(struct request_queue *q)
{
unsigned long flags;
WARN_ON(q->queuedata);
/* cause scsi_request_fn() to kill all non-finished requests */
spin_lock_irqsave(q->queue_lock, flags);
q->request_fn(q);
spin_unlock_irqrestore(q->queue_lock, flags);
blk_cleanup_queue(q);
}
/*
* Function: scsi_block_requests()
*
* Purpose: Utility function used by low-level drivers to prevent further
* commands from being queued to the device.
*
* Arguments: shost - Host in question
*
* Returns: Nothing
*
* Lock status: No locks are assumed held.
*
* Notes: There is no timer nor any other means by which the requests
* get unblocked other than the low-level driver calling
* scsi_unblock_requests().
*/
void scsi_block_requests(struct Scsi_Host *shost)
{
shost->host_self_blocked = 1;
}
EXPORT_SYMBOL(scsi_block_requests);
/*
* Function: scsi_unblock_requests()
*
* Purpose: Utility function used by low-level drivers to allow further
* commands from being queued to the device.
*
* Arguments: shost - Host in question
*
* Returns: Nothing
*
* Lock status: No locks are assumed held.
*
* Notes: There is no timer nor any other means by which the requests
* get unblocked other than the low-level driver calling
* scsi_unblock_requests().
*
* This is done as an API function so that changes to the
* internals of the scsi mid-layer won't require wholesale
* changes to drivers that use this feature.
*/
void scsi_unblock_requests(struct Scsi_Host *shost)
{
shost->host_self_blocked = 0;
scsi_run_host_queues(shost);
}
EXPORT_SYMBOL(scsi_unblock_requests);
int __init scsi_init_queue(void)
{
int i;
scsi_sdb_cache = kmem_cache_create("scsi_data_buffer",
sizeof(struct scsi_data_buffer),
0, 0, NULL);
if (!scsi_sdb_cache) {
printk(KERN_ERR "SCSI: can't init scsi sdb cache\n");
return -ENOMEM;
}
for (i = 0; i < SG_MEMPOOL_NR; i++) {
struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
int size = sgp->size * sizeof(struct scatterlist);
sgp->slab = kmem_cache_create(sgp->name, size, 0,
SLAB_HWCACHE_ALIGN, NULL);
if (!sgp->slab) {
printk(KERN_ERR "SCSI: can't init sg slab %s\n",
sgp->name);
goto cleanup_sdb;
}
sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
sgp->slab);
if (!sgp->pool) {
printk(KERN_ERR "SCSI: can't init sg mempool %s\n",
sgp->name);
goto cleanup_sdb;
}
}
return 0;
cleanup_sdb:
for (i = 0; i < SG_MEMPOOL_NR; i++) {
struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
if (sgp->pool)
mempool_destroy(sgp->pool);
if (sgp->slab)
kmem_cache_destroy(sgp->slab);
}
kmem_cache_destroy(scsi_sdb_cache);
return -ENOMEM;
}
void scsi_exit_queue(void)
{
int i;
kmem_cache_destroy(scsi_sdb_cache);
for (i = 0; i < SG_MEMPOOL_NR; i++) {
struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
mempool_destroy(sgp->pool);
kmem_cache_destroy(sgp->slab);
}
}
/**
* scsi_mode_select - issue a mode select
* @sdev: SCSI device to be queried
* @pf: Page format bit (1 == standard, 0 == vendor specific)
* @sp: Save page bit (0 == don't save, 1 == save)
* @modepage: mode page being requested
* @buffer: request buffer (may not be smaller than eight bytes)
* @len: length of request buffer.
* @timeout: command timeout
* @retries: number of retries before failing
* @data: returns a structure abstracting the mode header data
* @sshdr: place to put sense data (or NULL if no sense to be collected).
* must be SCSI_SENSE_BUFFERSIZE big.
*
* Returns zero if successful; negative error number or scsi
* status on error
*
*/
int
scsi_mode_select(struct scsi_device *sdev, int pf, int sp, int modepage,
unsigned char *buffer, int len, int timeout, int retries,
struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
{
unsigned char cmd[10];
unsigned char *real_buffer;
int ret;
memset(cmd, 0, sizeof(cmd));
cmd[1] = (pf ? 0x10 : 0) | (sp ? 0x01 : 0);
if (sdev->use_10_for_ms) {
if (len > 65535)
return -EINVAL;
real_buffer = kmalloc(8 + len, GFP_KERNEL);
if (!real_buffer)
return -ENOMEM;
memcpy(real_buffer + 8, buffer, len);
len += 8;
real_buffer[0] = 0;
real_buffer[1] = 0;
real_buffer[2] = data->medium_type;
real_buffer[3] = data->device_specific;
real_buffer[4] = data->longlba ? 0x01 : 0;
real_buffer[5] = 0;
real_buffer[6] = data->block_descriptor_length >> 8;
real_buffer[7] = data->block_descriptor_length;
cmd[0] = MODE_SELECT_10;
cmd[7] = len >> 8;
cmd[8] = len;
} else {
if (len > 255 || data->block_descriptor_length > 255 ||
data->longlba)
return -EINVAL;
real_buffer = kmalloc(4 + len, GFP_KERNEL);
if (!real_buffer)
return -ENOMEM;
memcpy(real_buffer + 4, buffer, len);
len += 4;
real_buffer[0] = 0;
real_buffer[1] = data->medium_type;
real_buffer[2] = data->device_specific;
real_buffer[3] = data->block_descriptor_length;
cmd[0] = MODE_SELECT;
cmd[4] = len;
}
ret = scsi_execute_req(sdev, cmd, DMA_TO_DEVICE, real_buffer, len,
sshdr, timeout, retries, NULL);
kfree(real_buffer);
return ret;
}
EXPORT_SYMBOL_GPL(scsi_mode_select);
/**
* scsi_mode_sense - issue a mode sense, falling back from 10 to six bytes if necessary.
* @sdev: SCSI device to be queried
* @dbd: set if mode sense will allow block descriptors to be returned
* @modepage: mode page being requested
* @buffer: request buffer (may not be smaller than eight bytes)
* @len: length of request buffer.
* @timeout: command timeout
* @retries: number of retries before failing
* @data: returns a structure abstracting the mode header data
* @sshdr: place to put sense data (or NULL if no sense to be collected).
* must be SCSI_SENSE_BUFFERSIZE big.
*
* Returns zero if unsuccessful, or the header offset (either 4
* or 8 depending on whether a six or ten byte command was
* issued) if successful.
*/
int
scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
unsigned char *buffer, int len, int timeout, int retries,
struct scsi_mode_data *data, struct scsi_sense_hdr *sshdr)
{
unsigned char cmd[12];
int use_10_for_ms;
int header_length;
int result;
struct scsi_sense_hdr my_sshdr;
memset(data, 0, sizeof(*data));
memset(&cmd[0], 0, 12);
cmd[1] = dbd & 0x18; /* allows DBD and LLBA bits */
cmd[2] = modepage;
/* caller might not be interested in sense, but we need it */
if (!sshdr)
sshdr = &my_sshdr;
retry:
use_10_for_ms = sdev->use_10_for_ms;
if (use_10_for_ms) {
if (len < 8)
len = 8;
cmd[0] = MODE_SENSE_10;
cmd[8] = len;
header_length = 8;
} else {
if (len < 4)
len = 4;
cmd[0] = MODE_SENSE;
cmd[4] = len;
header_length = 4;
}
memset(buffer, 0, len);
result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer, len,
sshdr, timeout, retries, NULL);
/* This code looks awful: what it's doing is making sure an
* ILLEGAL REQUEST sense return identifies the actual command
* byte as the problem. MODE_SENSE commands can return
* ILLEGAL REQUEST if the code page isn't supported */
if (use_10_for_ms && !scsi_status_is_good(result) &&
(driver_byte(result) & DRIVER_SENSE)) {
if (scsi_sense_valid(sshdr)) {
if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
(sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
/*
* Invalid command operation code
*/
sdev->use_10_for_ms = 0;
goto retry;
}
}
}
if(scsi_status_is_good(result)) {
if (unlikely(buffer[0] == 0x86 && buffer[1] == 0x0b &&
(modepage == 6 || modepage == 8))) {
/* Initio breakage? */
header_length = 0;
data->length = 13;
data->medium_type = 0;
data->device_specific = 0;
data->longlba = 0;
data->block_descriptor_length = 0;
} else if(use_10_for_ms) {
data->length = buffer[0]*256 + buffer[1] + 2;
data->medium_type = buffer[2];
data->device_specific = buffer[3];
data->longlba = buffer[4] & 0x01;
data->block_descriptor_length = buffer[6]*256
+ buffer[7];
} else {
data->length = buffer[0] + 1;
data->medium_type = buffer[1];
data->device_specific = buffer[2];
data->block_descriptor_length = buffer[3];
}
data->header_length = header_length;
}
return result;
}
EXPORT_SYMBOL(scsi_mode_sense);
/**
* scsi_test_unit_ready - test if unit is ready
* @sdev: scsi device to change the state of.
* @timeout: command timeout
* @retries: number of retries before failing
* @sshdr_external: Optional pointer to struct scsi_sense_hdr for
* returning sense. Make sure that this is cleared before passing
* in.
*
* Returns zero if unsuccessful or an error if TUR failed. For
* removable media, UNIT_ATTENTION sets ->changed flag.
**/
int
scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries,
struct scsi_sense_hdr *sshdr_external)
{
char cmd[] = {
TEST_UNIT_READY, 0, 0, 0, 0, 0,
};
struct scsi_sense_hdr *sshdr;
int result;
if (!sshdr_external)
sshdr = kzalloc(sizeof(*sshdr), GFP_KERNEL);
else
sshdr = sshdr_external;
/* try to eat the UNIT_ATTENTION if there are enough retries */
do {
result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, sshdr,
timeout, retries, NULL);
if (sdev->removable && scsi_sense_valid(sshdr) &&
sshdr->sense_key == UNIT_ATTENTION)
sdev->changed = 1;
} while (scsi_sense_valid(sshdr) &&
sshdr->sense_key == UNIT_ATTENTION && --retries);
if (!sshdr_external)
kfree(sshdr);
return result;
}
EXPORT_SYMBOL(scsi_test_unit_ready);
/**
* scsi_device_set_state - Take the given device through the device state model.
* @sdev: scsi device to change the state of.
* @state: state to change to.
*
* Returns zero if unsuccessful or an error if the requested
* transition is illegal.
*/
int
scsi_device_set_state(struct scsi_device *sdev, enum scsi_device_state state)
{
enum scsi_device_state oldstate = sdev->sdev_state;
if (state == oldstate)
return 0;
switch (state) {
case SDEV_CREATED:
switch (oldstate) {
case SDEV_CREATED_BLOCK:
break;
default:
goto illegal;
}
break;
case SDEV_RUNNING:
switch (oldstate) {
case SDEV_CREATED:
case SDEV_OFFLINE:
case SDEV_QUIESCE:
case SDEV_BLOCK:
break;
default:
goto illegal;
}
break;
case SDEV_QUIESCE:
switch (oldstate) {
case SDEV_RUNNING:
case SDEV_OFFLINE:
break;
default:
goto illegal;
}
break;
case SDEV_OFFLINE:
switch (oldstate) {
case SDEV_CREATED:
case SDEV_RUNNING:
case SDEV_QUIESCE:
case SDEV_BLOCK:
break;
default:
goto illegal;
}
break;
case SDEV_BLOCK:
switch (oldstate) {
case SDEV_RUNNING:
case SDEV_CREATED_BLOCK:
break;
default:
goto illegal;
}
break;
case SDEV_CREATED_BLOCK:
switch (oldstate) {
case SDEV_CREATED:
break;
default:
goto illegal;
}
break;
case SDEV_CANCEL:
switch (oldstate) {
case SDEV_CREATED:
case SDEV_RUNNING:
case SDEV_QUIESCE:
case SDEV_OFFLINE:
case SDEV_BLOCK:
break;
default:
goto illegal;
}
break;
case SDEV_DEL:
switch (oldstate) {
case SDEV_CREATED:
case SDEV_RUNNING:
case SDEV_OFFLINE:
case SDEV_CANCEL:
break;
default:
goto illegal;
}
break;
}
sdev->sdev_state = state;
return 0;
illegal:
SCSI_LOG_ERROR_RECOVERY(1,
sdev_printk(KERN_ERR, sdev,
"Illegal state transition %s->%s\n",
scsi_device_state_name(oldstate),
scsi_device_state_name(state))
);
return -EINVAL;
}
EXPORT_SYMBOL(scsi_device_set_state);
/**
* sdev_evt_emit - emit a single SCSI device uevent
* @sdev: associated SCSI device
* @evt: event to emit
*
* Send a single uevent (scsi_event) to the associated scsi_device.
*/
static void scsi_evt_emit(struct scsi_device *sdev, struct scsi_event *evt)
{
int idx = 0;
char *envp[3];
switch (evt->evt_type) {
case SDEV_EVT_MEDIA_CHANGE:
envp[idx++] = "SDEV_MEDIA_CHANGE=1";
break;
default:
/* do nothing */
break;
}
envp[idx++] = NULL;
kobject_uevent_env(&sdev->sdev_gendev.kobj, KOBJ_CHANGE, envp);
}
/**
* sdev_evt_thread - send a uevent for each scsi event
* @work: work struct for scsi_device
*
* Dispatch queued events to their associated scsi_device kobjects
* as uevents.
*/
void scsi_evt_thread(struct work_struct *work)
{
struct scsi_device *sdev;
LIST_HEAD(event_list);
sdev = container_of(work, struct scsi_device, event_work);
while (1) {
struct scsi_event *evt;
struct list_head *this, *tmp;
unsigned long flags;
spin_lock_irqsave(&sdev->list_lock, flags);
list_splice_init(&sdev->event_list, &event_list);
spin_unlock_irqrestore(&sdev->list_lock, flags);
if (list_empty(&event_list))
break;
list_for_each_safe(this, tmp, &event_list) {
evt = list_entry(this, struct scsi_event, node);
list_del(&evt->node);
scsi_evt_emit(sdev, evt);
kfree(evt);
}
}
}
/**
* sdev_evt_send - send asserted event to uevent thread
* @sdev: scsi_device event occurred on
* @evt: event to send
*
* Assert scsi device event asynchronously.
*/
void sdev_evt_send(struct scsi_device *sdev, struct scsi_event *evt)
{
unsigned long flags;
#if 0
/* FIXME: currently this check eliminates all media change events
* for polled devices. Need to update to discriminate between AN
* and polled events */
if (!test_bit(evt->evt_type, sdev->supported_events)) {
kfree(evt);
return;
}
#endif
spin_lock_irqsave(&sdev->list_lock, flags);
list_add_tail(&evt->node, &sdev->event_list);
schedule_work(&sdev->event_work);
spin_unlock_irqrestore(&sdev->list_lock, flags);
}
EXPORT_SYMBOL_GPL(sdev_evt_send);
/**
* sdev_evt_alloc - allocate a new scsi event
* @evt_type: type of event to allocate
* @gfpflags: GFP flags for allocation
*
* Allocates and returns a new scsi_event.
*/
struct scsi_event *sdev_evt_alloc(enum scsi_device_event evt_type,
gfp_t gfpflags)
{
struct scsi_event *evt = kzalloc(sizeof(struct scsi_event), gfpflags);
if (!evt)
return NULL;
evt->evt_type = evt_type;
INIT_LIST_HEAD(&evt->node);
/* evt_type-specific initialization, if any */
switch (evt_type) {
case SDEV_EVT_MEDIA_CHANGE:
default:
/* do nothing */
break;
}
return evt;
}
EXPORT_SYMBOL_GPL(sdev_evt_alloc);
/**
* sdev_evt_send_simple - send asserted event to uevent thread
* @sdev: scsi_device event occurred on
* @evt_type: type of event to send
* @gfpflags: GFP flags for allocation
*
* Assert scsi device event asynchronously, given an event type.
*/
void sdev_evt_send_simple(struct scsi_device *sdev,
enum scsi_device_event evt_type, gfp_t gfpflags)
{
struct scsi_event *evt = sdev_evt_alloc(evt_type, gfpflags);
if (!evt) {
sdev_printk(KERN_ERR, sdev, "event %d eaten due to OOM\n",
evt_type);
return;
}
sdev_evt_send(sdev, evt);
}
EXPORT_SYMBOL_GPL(sdev_evt_send_simple);
/**
* scsi_device_quiesce - Block user issued commands.
* @sdev: scsi device to quiesce.
*
* This works by trying to transition to the SDEV_QUIESCE state
* (which must be a legal transition). When the device is in this
* state, only special requests will be accepted, all others will
* be deferred. Since special requests may also be requeued requests,
* a successful return doesn't guarantee the device will be
* totally quiescent.
*
* Must be called with user context, may sleep.
*
* Returns zero if unsuccessful or an error if not.
*/
int
scsi_device_quiesce(struct scsi_device *sdev)
{
int err = scsi_device_set_state(sdev, SDEV_QUIESCE);
if (err)
return err;
scsi_run_queue(sdev->request_queue);
while (sdev->device_busy) {
msleep_interruptible(200);
scsi_run_queue(sdev->request_queue);
}
return 0;
}
EXPORT_SYMBOL(scsi_device_quiesce);
/**
* scsi_device_resume - Restart user issued commands to a quiesced device.
* @sdev: scsi device to resume.
*
* Moves the device from quiesced back to running and restarts the
* queues.
*
* Must be called with user context, may sleep.
*/
void scsi_device_resume(struct scsi_device *sdev)
{
/* check if the device state was mutated prior to resume, and if
* so assume the state is being managed elsewhere (for example
* device deleted during suspend)
*/
if (sdev->sdev_state != SDEV_QUIESCE ||
scsi_device_set_state(sdev, SDEV_RUNNING))
return;
scsi_run_queue(sdev->request_queue);
}
EXPORT_SYMBOL(scsi_device_resume);
static void
device_quiesce_fn(struct scsi_device *sdev, void *data)
{
scsi_device_quiesce(sdev);
}
void
scsi_target_quiesce(struct scsi_target *starget)
{
starget_for_each_device(starget, NULL, device_quiesce_fn);
}
EXPORT_SYMBOL(scsi_target_quiesce);
static void
device_resume_fn(struct scsi_device *sdev, void *data)
{
scsi_device_resume(sdev);
}
void
scsi_target_resume(struct scsi_target *starget)
{
starget_for_each_device(starget, NULL, device_resume_fn);
}
EXPORT_SYMBOL(scsi_target_resume);
/**
* scsi_internal_device_block - internal function to put a device temporarily into the SDEV_BLOCK state
* @sdev: device to block
*
* Block request made by scsi lld's to temporarily stop all
* scsi commands on the specified device. Called from interrupt
* or normal process context.
*
* Returns zero if successful or error if not
*
* Notes:
* This routine transitions the device to the SDEV_BLOCK state
* (which must be a legal transition). When the device is in this
* state, all commands are deferred until the scsi lld reenables
* the device with scsi_device_unblock or device_block_tmo fires.
* This routine assumes the host_lock is held on entry.
*/
int
scsi_internal_device_block(struct scsi_device *sdev)
{
struct request_queue *q = sdev->request_queue;
unsigned long flags;
int err = 0;
err = scsi_device_set_state(sdev, SDEV_BLOCK);
if (err) {
err = scsi_device_set_state(sdev, SDEV_CREATED_BLOCK);
if (err)
return err;
}
/*
* The device has transitioned to SDEV_BLOCK. Stop the
* block layer from calling the midlayer with this device's
* request queue.
*/
spin_lock_irqsave(q->queue_lock, flags);
blk_stop_queue(q);
spin_unlock_irqrestore(q->queue_lock, flags);
return 0;
}
EXPORT_SYMBOL_GPL(scsi_internal_device_block);
/**
* scsi_internal_device_unblock - resume a device after a block request
* @sdev: device to resume
*
* Called by scsi lld's or the midlayer to restart the device queue
* for the previously suspended scsi device. Called from interrupt or
* normal process context.
*
* Returns zero if successful or error if not.
*
* Notes:
* This routine transitions the device to the SDEV_RUNNING state
* (which must be a legal transition) allowing the midlayer to
* goose the queue for this device. This routine assumes the
* host_lock is held upon entry.
*/
int
scsi_internal_device_unblock(struct scsi_device *sdev)
{
struct request_queue *q = sdev->request_queue;
unsigned long flags;
/*
* Try to transition the scsi device to SDEV_RUNNING
* and goose the device queue if successful.
*/
if (sdev->sdev_state == SDEV_BLOCK)
sdev->sdev_state = SDEV_RUNNING;
else if (sdev->sdev_state == SDEV_CREATED_BLOCK)
sdev->sdev_state = SDEV_CREATED;
else if (sdev->sdev_state != SDEV_CANCEL &&
sdev->sdev_state != SDEV_OFFLINE)
return -EINVAL;
spin_lock_irqsave(q->queue_lock, flags);
blk_start_queue(q);
spin_unlock_irqrestore(q->queue_lock, flags);
return 0;
}
EXPORT_SYMBOL_GPL(scsi_internal_device_unblock);
static void
device_block(struct scsi_device *sdev, void *data)
{
scsi_internal_device_block(sdev);
}
static int
target_block(struct device *dev, void *data)
{
if (scsi_is_target_device(dev))
starget_for_each_device(to_scsi_target(dev), NULL,
device_block);
return 0;
}
void
scsi_target_block(struct device *dev)
{
if (scsi_is_target_device(dev))
starget_for_each_device(to_scsi_target(dev), NULL,
device_block);
else
device_for_each_child(dev, NULL, target_block);
}
EXPORT_SYMBOL_GPL(scsi_target_block);
static void
device_unblock(struct scsi_device *sdev, void *data)
{
scsi_internal_device_unblock(sdev);
}
static int
target_unblock(struct device *dev, void *data)
{
if (scsi_is_target_device(dev))
starget_for_each_device(to_scsi_target(dev), NULL,
device_unblock);
return 0;
}
void
scsi_target_unblock(struct device *dev)
{
if (scsi_is_target_device(dev))
starget_for_each_device(to_scsi_target(dev), NULL,
device_unblock);
else
device_for_each_child(dev, NULL, target_unblock);
}
EXPORT_SYMBOL_GPL(scsi_target_unblock);
/**
* scsi_kmap_atomic_sg - find and atomically map an sg-elemnt
* @sgl: scatter-gather list
* @sg_count: number of segments in sg
* @offset: offset in bytes into sg, on return offset into the mapped area
* @len: bytes to map, on return number of bytes mapped
*
* Returns virtual address of the start of the mapped page
*/
void *scsi_kmap_atomic_sg(struct scatterlist *sgl, int sg_count,
size_t *offset, size_t *len)
{
int i;
size_t sg_len = 0, len_complete = 0;
struct scatterlist *sg;
struct page *page;
WARN_ON(!irqs_disabled());
for_each_sg(sgl, sg, sg_count, i) {
len_complete = sg_len; /* Complete sg-entries */
sg_len += sg->length;
if (sg_len > *offset)
break;
}
if (unlikely(i == sg_count)) {
printk(KERN_ERR "%s: Bytes in sg: %zu, requested offset %zu, "
"elements %d\n",
__func__, sg_len, *offset, sg_count);
WARN_ON(1);
return NULL;
}
/* Offset starting from the beginning of first page in this sg-entry */
*offset = *offset - len_complete + sg->offset;
/* Assumption: contiguous pages can be accessed as "page + i" */
page = nth_page(sg_page(sg), (*offset >> PAGE_SHIFT));
*offset &= ~PAGE_MASK;
/* Bytes in this sg-entry from *offset to the end of the page */
sg_len = PAGE_SIZE - *offset;
if (*len > sg_len)
*len = sg_len;
return kmap_atomic(page);
}
EXPORT_SYMBOL(scsi_kmap_atomic_sg);
/**
* scsi_kunmap_atomic_sg - atomically unmap a virtual address, previously mapped with scsi_kmap_atomic_sg
* @virt: virtual address to be unmapped
*/
void scsi_kunmap_atomic_sg(void *virt)
{
kunmap_atomic(virt);
}
EXPORT_SYMBOL(scsi_kunmap_atomic_sg);