Release 4.12 block/bsg.c

/*
 * bsg.c - block layer implementation of the sg v4 interface
 *
 * Copyright (C) 2004 Jens Axboe <axboe@suse.de> SUSE Labs
 * Copyright (C) 2004 Peter M. Jones <pjones@redhat.com>
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License version 2.  See the file "COPYING" in the main directory of this
 *  archive for more details.
 *
 */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/blkdev.h>
#include <linux/poll.h>
#include <linux/cdev.h>
#include <linux/jiffies.h>
#include <linux/percpu.h>
#include <linux/uio.h>
#include <linux/idr.h>
#include <linux/bsg.h>
#include <linux/slab.h>

#include <scsi/scsi.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_driver.h>
#include <scsi/sg.h>


#define BSG_DESCRIPTION	"Block layer SCSI generic (bsg) driver"

#define BSG_VERSION	"0.4"


struct bsg_device {
	
struct request_queue *queue;
	
spinlock_t lock;
	
struct list_head busy_list;
	
struct list_head done_list;
	
struct hlist_node dev_list;
	
atomic_t ref_count;
	
int queued_cmds;
	
int done_cmds;
	
wait_queue_head_t wq_done;
	
wait_queue_head_t wq_free;
	
char name[20];
	
int max_queue;
	
unsigned long flags;
};

enum {
	
BSG_F_BLOCK		= 1,
};


#define BSG_DEFAULT_CMDS	64

#define BSG_MAX_DEVS		32768


#undef BSG_DEBUG

#ifdef BSG_DEBUG

#define dprintk(fmt, args...) printk(KERN_ERR "%s: " fmt, __func__, ##args)
#else

#define dprintk(fmt, args...)
#endif

static DEFINE_MUTEX(bsg_mutex);
static DEFINE_IDR(bsg_minor_idr);


#define BSG_LIST_ARRAY_SIZE	8

static struct hlist_head bsg_device_list[BSG_LIST_ARRAY_SIZE];


static struct class *bsg_class;

static int bsg_major;


static struct kmem_cache *bsg_cmd_cachep;

/*
 * our internal command type
 */

struct bsg_command {
	
struct bsg_device *bd;
	
struct list_head list;
	
struct request *rq;
	
struct bio *bio;
	
struct bio *bidi_bio;
	
int err;
	
struct sg_io_v4 hdr;
};



static void bsg_free_command(struct bsg_command *bc)
{
	struct bsg_device *bd = bc->bd;
	unsigned long flags;

	kmem_cache_free(bsg_cmd_cachep, bc);

	spin_lock_irqsave(&bd->lock, flags);
	bd->queued_cmds--;
	spin_unlock_irqrestore(&bd->lock, flags);

	wake_up(&bd->wq_free);
}

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static struct bsg_command *bsg_alloc_command(struct bsg_device *bd)
{
	struct bsg_command *bc = ERR_PTR(-EINVAL);

	spin_lock_irq(&bd->lock);

	if (bd->queued_cmds >= bd->max_queue)
		goto out;

	bd->queued_cmds++;
	spin_unlock_irq(&bd->lock);

	bc = kmem_cache_zalloc(bsg_cmd_cachep, GFP_KERNEL);
	if (unlikely(!bc)) {
		spin_lock_irq(&bd->lock);
		bd->queued_cmds--;
		bc = ERR_PTR(-ENOMEM);
		goto out;
	}

	bc->bd = bd;
	INIT_LIST_HEAD(&bc->list);
	dprintk("%s: returning free cmd %p\n", bd->name, bc);
	return bc;
out:
	spin_unlock_irq(&bd->lock);
	return bc;
}

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static inline struct hlist_head *bsg_dev_idx_hash(int index)
{
	return &bsg_device_list[index & (BSG_LIST_ARRAY_SIZE - 1)];
}

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static int blk_fill_sgv4_hdr_rq(struct request_queue *q, struct request *rq,
				struct sg_io_v4 *hdr, struct bsg_device *bd,
				fmode_t has_write_perm)
{
	struct scsi_request *req = scsi_req(rq);

	if (hdr->request_len > BLK_MAX_CDB) {
		req->cmd = kzalloc(hdr->request_len, GFP_KERNEL);
		if (!req->cmd)
			return -ENOMEM;
	}

	if (copy_from_user(req->cmd, (void __user *)(unsigned long)hdr->request,
			   hdr->request_len))
		return -EFAULT;

	if (hdr->subprotocol == BSG_SUB_PROTOCOL_SCSI_CMD) {
		if (blk_verify_command(req->cmd, has_write_perm))
			return -EPERM;
	} else if (!capable(CAP_SYS_RAWIO))
		return -EPERM;

	/*
         * fill in request structure
         */
	req->cmd_len = hdr->request_len;

	rq->timeout = msecs_to_jiffies(hdr->timeout);
	if (!rq->timeout)
		rq->timeout = q->sg_timeout;
	if (!rq->timeout)
		rq->timeout = BLK_DEFAULT_SG_TIMEOUT;
	if (rq->timeout < BLK_MIN_SG_TIMEOUT)
		rq->timeout = BLK_MIN_SG_TIMEOUT;

	return 0;
}

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1.94%
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9.09%
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3
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1
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9.09%
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/*
 * Check if sg_io_v4 from user is allowed and valid
 */

static int

bsg_validate_sgv4_hdr(struct sg_io_v4 *hdr, int *op)
{
	int ret = 0;

	if (hdr->guard != 'Q')
		return -EINVAL;

	switch (hdr->protocol) {
	case BSG_PROTOCOL_SCSI:
		switch (hdr->subprotocol) {
		case BSG_SUB_PROTOCOL_SCSI_CMD:
		case BSG_SUB_PROTOCOL_SCSI_TRANSPORT:
			break;
		default:
			ret = -EINVAL;
		}
		break;
	default:
		ret = -EINVAL;
	}

	*op = hdr->dout_xfer_len ? REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN;
	return ret;
}

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5
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/*
 * map sg_io_v4 to a request.
 */

static struct request *

bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr, fmode_t has_write_perm)
{
	struct request_queue *q = bd->queue;
	struct request *rq, *next_rq = NULL;
	int ret;
	unsigned int op, dxfer_len;
	void __user *dxferp = NULL;
	struct bsg_class_device *bcd = &q->bsg_dev;

	/* if the LLD has been removed then the bsg_unregister_queue will
         * eventually be called and the class_dev was freed, so we can no
         * longer use this request_queue. Return no such address.
         */
	if (!bcd->class_dev)
		return ERR_PTR(-ENXIO);

	dprintk("map hdr %llx/%u %llx/%u\n", (unsigned long long) hdr->dout_xferp,
		hdr->dout_xfer_len, (unsigned long long) hdr->din_xferp,
		hdr->din_xfer_len);

	ret = bsg_validate_sgv4_hdr(hdr, &op);
	if (ret)
		return ERR_PTR(ret);

	/*
         * map scatter-gather elements separately and string them to request
         */
	rq = blk_get_request(q, op, GFP_KERNEL);
	if (IS_ERR(rq))
		return rq;
	scsi_req_init(rq);

	ret = blk_fill_sgv4_hdr_rq(q, rq, hdr, bd, has_write_perm);
	if (ret)
		goto out;

	if (op == REQ_OP_SCSI_OUT && hdr->din_xfer_len) {
		if (!test_bit(QUEUE_FLAG_BIDI, &q->queue_flags)) {
			ret = -EOPNOTSUPP;
			goto out;
		}

		next_rq = blk_get_request(q, REQ_OP_SCSI_IN, GFP_KERNEL);
		if (IS_ERR(next_rq)) {
			ret = PTR_ERR(next_rq);
			next_rq = NULL;
			goto out;
		}
		rq->next_rq = next_rq;

		dxferp = (void __user *)(unsigned long)hdr->din_xferp;
		ret =  blk_rq_map_user(q, next_rq, NULL, dxferp,
				       hdr->din_xfer_len, GFP_KERNEL);
		if (ret)
			goto out;
	}

	if (hdr->dout_xfer_len) {
		dxfer_len = hdr->dout_xfer_len;
		dxferp = (void __user *)(unsigned long)hdr->dout_xferp;
	} else if (hdr->din_xfer_len) {
		dxfer_len = hdr->din_xfer_len;
		dxferp = (void __user *)(unsigned long)hdr->din_xferp;
	} else
		dxfer_len = 0;

	if (dxfer_len) {
		ret = blk_rq_map_user(q, rq, NULL, dxferp, dxfer_len,
				      GFP_KERNEL);
		if (ret)
			goto out;
	}

	return rq;
out:
	scsi_req_free_cmd(scsi_req(rq));
	blk_put_request(rq);
	if (next_rq) {
		blk_rq_unmap_user(next_rq->bio);
		blk_put_request(next_rq);
	}
	return ERR_PTR(ret);
}

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/*
 * async completion call-back from the block layer, when scsi/ide/whatever
 * calls end_that_request_last() on a request
 */


static void bsg_rq_end_io(struct request *rq, int uptodate)
{
	struct bsg_command *bc = rq->end_io_data;
	struct bsg_device *bd = bc->bd;
	unsigned long flags;

	dprintk("%s: finished rq %p bc %p, bio %p stat %d\n",
		bd->name, rq, bc, bc->bio, uptodate);

	bc->hdr.duration = jiffies_to_msecs(jiffies - bc->hdr.duration);

	spin_lock_irqsave(&bd->lock, flags);
	list_move_tail(&bc->list, &bd->done_list);
	bd->done_cmds++;
	spin_unlock_irqrestore(&bd->lock, flags);

	wake_up(&bd->wq_done);
}

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/*
 * do final setup of a 'bc' and submit the matching 'rq' to the block
 * layer for io
 */


static void bsg_add_command(struct bsg_device *bd, struct request_queue *q,
			    struct bsg_command *bc, struct request *rq)
{
	int at_head = (0 == (bc->hdr.flags & BSG_FLAG_Q_AT_TAIL));

	/*
         * add bc command to busy queue and submit rq for io
         */
	bc->rq = rq;
	bc->bio = rq->bio;
	if (rq->next_rq)
		bc->bidi_bio = rq->next_rq->bio;
	bc->hdr.duration = jiffies;
	spin_lock_irq(&bd->lock);
	list_add_tail(&bc->list, &bd->busy_list);
	spin_unlock_irq(&bd->lock);

	dprintk("%s: queueing rq %p, bc %p\n", bd->name, rq, bc);

	rq->end_io_data = bc;
	blk_execute_rq_nowait(q, NULL, rq, at_head, bsg_rq_end_io);
}

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static struct bsg_command *bsg_next_done_cmd(struct bsg_device *bd)
{
	struct bsg_command *bc = NULL;

	spin_lock_irq(&bd->lock);
	if (bd->done_cmds) {
		bc = list_first_entry(&bd->done_list, struct bsg_command, list);
		list_del(&bc->list);
		bd->done_cmds--;
	}
	spin_unlock_irq(&bd->lock);

	return bc;
}

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/*
 * Get a finished command from the done list
 */


static struct bsg_command *bsg_get_done_cmd(struct bsg_device *bd)
{
	struct bsg_command *bc;
	int ret;

	do {
		bc = bsg_next_done_cmd(bd);
		if (bc)
			break;

		if (!test_bit(BSG_F_BLOCK, &bd->flags)) {
			bc = ERR_PTR(-EAGAIN);
			break;
		}

		ret = wait_event_interruptible(bd->wq_done, bd->done_cmds);
		if (ret) {
			bc = ERR_PTR(-ERESTARTSYS);
			break;
		}
	} while (1);

	dprintk("%s: returning done %p\n", bd->name, bc);

	return bc;
}

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static int blk_complete_sgv4_hdr_rq(struct request *rq, struct sg_io_v4 *hdr,
				    struct bio *bio, struct bio *bidi_bio)
{
	struct scsi_request *req = scsi_req(rq);
	int ret = 0;

	dprintk("rq %p bio %p 0x%x\n", rq, bio, req->result);
	/*
         * fill in all the output members
         */
	hdr->device_status = req->result & 0xff;
	hdr->transport_status = host_byte(req->result);
	hdr->driver_status = driver_byte(req->result);
	hdr->info = 0;
	if (hdr->device_status || hdr->transport_status || hdr->driver_status)
		hdr->info |= SG_INFO_CHECK;
	hdr->response_len = 0;

	if (req->sense_len && hdr->response) {
		int len = min_t(unsigned int, hdr->max_response_len,
					req->sense_len);

		ret = copy_to_user((void __user *)(unsigned long)hdr->response,
				   req->sense, len);
		if (!ret)
			hdr->response_len = len;
		else
			ret = -EFAULT;
	}

	if (rq->next_rq) {
		hdr->dout_resid = req->resid_len;
		hdr->din_resid = scsi_req(rq->next_rq)->resid_len;
		blk_rq_unmap_user(bidi_bio);
		blk_put_request(rq->next_rq);
	} else if (rq_data_dir(rq) == READ)
		hdr->din_resid = req->resid_len;
	else
		hdr->dout_resid = req->resid_len;

	/*
         * If the request generated a negative error number, return it
         * (providing we aren't already returning an error); if it's
         * just a protocol response (i.e. non negative), that gets
         * processed above.
         */
	if (!ret && req->result < 0)
		ret = req->result;

	blk_rq_unmap_user(bio);
	scsi_req_free_cmd(req);
	blk_put_request(rq);

	return ret;
}

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static bool bsg_complete(struct bsg_device *bd)
{
	bool ret = false;
	bool spin;

	do {
		spin_lock_irq(&bd->lock);

		BUG_ON(bd->done_cmds > bd->queued_cmds);

		/*
                 * All commands consumed.
                 */
		if (bd->done_cmds == bd->queued_cmds)
			ret = true;

		spin = !test_bit(BSG_F_BLOCK, &bd->flags);

		spin_unlock_irq(&bd->lock);
	} while (!ret && spin);

	return ret;
}

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static int bsg_complete_all_commands(struct bsg_device *bd)
{
	struct bsg_command *bc;
	int ret, tret;

	dprintk("%s: entered\n", bd->name);

	/*
         * wait for all commands to complete
         */
	io_wait_event(bd->wq_done, bsg_complete(bd));

	/*
         * discard done commands
         */
	ret = 0;
	do {
		spin_lock_irq(&bd->lock);
		if (!bd->queued_cmds) {
			spin_unlock_irq(&bd->lock);
			break;
		}
		spin_unlock_irq(&bd->lock);

		bc = bsg_get_done_cmd(bd);
		if (IS_ERR(bc))
			break;

		tret = blk_complete_sgv4_hdr_rq(bc->rq, &bc->hdr, bc->bio,
						bc->bidi_bio);
		if (!ret)
			ret = tret;

		bsg_free_command(bc);
	} while (1);

	return ret;
}

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1
16.67%
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100.00%


static int

__bsg_read(char __user *buf, size_t count, struct bsg_device *bd,
	   const struct iovec *iov, ssize_t *bytes_read)
{
	struct bsg_command *bc;
	int nr_commands, ret;

	if (count % sizeof(struct sg_io_v4))
		return -EINVAL;

	ret = 0;
	nr_commands = count / sizeof(struct sg_io_v4);
	while (nr_commands) {
		bc = bsg_get_done_cmd(bd);
		if (IS_ERR(bc)) {
			ret = PTR_ERR(bc);
			break;
		}

		/*
                 * this is the only case where we need to copy data back
                 * after completing the request. so do that here,
                 * bsg_complete_work() cannot do that for us
                 */
		ret = blk_complete_sgv4_hdr_rq(bc->rq, &bc->hdr, bc->bio,
					       bc->bidi_bio);

		if (copy_to_user(buf, &bc->hdr, sizeof(bc->hdr)))
			ret = -EFAULT;

		bsg_free_command(bc);

		if (ret)
			break;

		buf += sizeof(struct sg_io_v4);
		*bytes_read += sizeof(struct sg_io_v4);
		nr_commands--;
	}

	return ret;
}

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static inline void bsg_set_block(struct bsg_device *bd, struct file *file)
{
	if (file->f_flags & O_NONBLOCK)
		clear_bit(BSG_F_BLOCK, &bd->flags);
	else
		set_bit(BSG_F_BLOCK, &bd->flags);
}

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/*
 * Check if the error is a "real" error that we should return.
 */


static inline int err_block_err(int ret)
{
	if (ret && ret != -ENOSPC && ret != -ENODATA && ret != -EAGAIN)
		return 1;

	return 0;
}

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static ssize_t

bsg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
	struct bsg_device *bd = file->private_data;
	int ret;
	ssize_t bytes_read;

	dprintk("%s: read %zd bytes\n", bd->name, count);

	bsg_set_block(bd, file);

	bytes_read = 0;
	ret = __bsg_read(buf, count, bd, NULL, &bytes_read);
	*ppos = bytes_read;

	if (!bytes_read || err_block_err(ret))
		bytes_read = ret;

	return bytes_read;
}

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static int __bsg_write(struct bsg_device *bd, const char __user *buf,
		       size_t count, ssize_t *bytes_written,
		       fmode_t has_write_perm)
{
	struct bsg_command *bc;
	struct request *rq;
	int ret, nr_commands;

	if (count % sizeof(struct sg_io_v4))
		return -EINVAL;

	nr_commands = count / sizeof(struct sg_io_v4);
	rq = NULL;
	bc = NULL;
	ret = 0;
	while (nr_commands) {
		struct request_queue *q = bd->queue;

		bc = bsg_alloc_command(bd);
		if (IS_ERR(bc)) {
			ret = PTR_ERR(bc);
			bc = NULL;
			break;
		}

		if (copy_from_user(&bc->hdr, buf, sizeof(bc->hdr))) {
			ret = -EFAULT;
			break;
		}

		/*
                 * get a request, fill in the blanks, and add to request queue
                 */
		rq = bsg_map_hdr(bd, &bc->hdr, has_write_perm);
		if (IS_ERR(rq)) {
			ret = PTR_ERR(rq);
			rq = NULL;
			break;
		}

		bsg_add_command(bd, q, bc, rq);
		bc = NULL;
		rq = NULL;
		nr_commands--;
		buf += sizeof(struct sg_io_v4);
		*bytes_written += sizeof(struct sg_io_v4);
	}

	if (bc)
		bsg_free_command(bc);

	return ret;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Jens Axboe
225
95.74%
3
42.86%
FUJITA Tomonori
9
3.83%
3
42.86%
Al Viro
1
0.43%
1
14.29%
Total
235
100.00%
7
100.00%


static ssize_t

bsg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
	struct bsg_device *bd = file->private_data;
	ssize_t bytes_written;
	int ret;

	dprintk("%s: write %zd bytes\n", bd->name, count);

	if (unlikely(uaccess_kernel()))
		return -EINVAL;

	bsg_set_block(bd, file);

	bytes_written = 0;
	ret = __bsg_write(bd, buf, count, &bytes_written,
			  file->f_mode & FMODE_WRITE);

	*ppos = bytes_written;

	/*
         * return bytes written on non-fatal errors
         */
	if (!