1 files changed, 230 insertions, 194 deletions

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 32425ac..2e01a9d 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -49,6 +49,7 @@ static int sg_version_num = 30536;	/* 2 digits for each component */
 #include <linux/delay.h>
 #include <linux/blktrace_api.h>
 #include <linux/mutex.h>
+#include <linux/atomic.h>
 #include <linux/ratelimit.h>
 
 #include "scsi.h"
@@ -106,18 +107,16 @@ static int scatter_elem_sz_prev = SG_SCATTER_SZ;
 
 #define SG_SECTOR_SZ 512
 
-static int sg_add(struct device *, struct class_interface *);
-static void sg_remove(struct device *, struct class_interface *);
-
-static DEFINE_SPINLOCK(sg_open_exclusive_lock);
+static int sg_add_device(struct device *, struct class_interface *);
+static void sg_remove_device(struct device *, struct class_interface *);
 
 static DEFINE_IDR(sg_index_idr);
 static DEFINE_RWLOCK(sg_index_lock);	/* Also used to lock
 							   file descriptor list for device */
 
 static struct class_interface sg_interface = {
-	.add_dev	= sg_add,
-	.remove_dev	= sg_remove,
+	.add_dev        = sg_add_device,
+	.remove_dev     = sg_remove_device,
 };
 
 typedef struct sg_scatter_hold { /* holding area for scsi scatter gather info */
@@ -150,8 +149,7 @@ typedef struct sg_request {	/* SG_MAX_QUEUE requests outstanding per file */
 } Sg_request;
 
 typedef struct sg_fd {		/* holds the state of a file descriptor */
-	/* sfd_siblings is protected by sg_index_lock */
-	struct list_head sfd_siblings;
+	struct list_head sfd_siblings;  /* protected by device's sfd_lock */
 	struct sg_device *parentdp;	/* owning device */
 	wait_queue_head_t read_wait;	/* queue read until command done */
 	rwlock_t rq_list_lock;	/* protect access to list in req_arr */
@@ -174,14 +172,15 @@ typedef struct sg_fd {		/* holds the state of a file descriptor */
 
 typedef struct sg_device { /* holds the state of each scsi generic device */
 	struct scsi_device *device;
-	wait_queue_head_t o_excl_wait;	/* queue open() when O_EXCL in use */
+	wait_queue_head_t open_wait;    /* queue open() when O_EXCL present */
+	struct mutex open_rel_lock;     /* held when in open() or release() */
 	int sg_tablesize;	/* adapter's max scatter-gather table size */
 	u32 index;		/* device index number */
-	/* sfds is protected by sg_index_lock */
 	struct list_head sfds;
-	volatile char detached;	/* 0->attached, 1->detached pending removal */
-	/* exclude protected by sg_open_exclusive_lock */
-	char exclude;		/* opened for exclusive access */
+	rwlock_t sfd_lock;      /* protect access to sfd list */
+	atomic_t detaching;     /* 0->device usable, 1->device detaching */
+	bool exclude;		/* 1->open(O_EXCL) succeeded and is active */
+	int open_cnt;		/* count of opens (perhaps < num(sfds) ) */
 	char sgdebug;		/* 0->off, 1->sense, 9->dump dev, 10-> all devs */
 	struct gendisk *disk;
 	struct cdev * cdev;	/* char_dev [sysfs: /sys/cdev/major/sg<n>] */
@@ -212,7 +211,7 @@ static Sg_request *sg_add_request(Sg_fd * sfp);
 static int sg_remove_request(Sg_fd * sfp, Sg_request * srp);
 static int sg_res_in_use(Sg_fd * sfp);
 static Sg_device *sg_get_dev(int dev);
-static void sg_put_dev(Sg_device *sdp);
+static void sg_device_destroy(struct kref *kref);
 
 #define SZ_SG_HEADER sizeof(struct sg_header)
 #define SZ_SG_IO_HDR sizeof(sg_io_hdr_t)
@@ -229,38 +228,43 @@ static int sg_allow_access(struct file *filp, unsigned char *cmd)
 	return blk_verify_command(cmd, filp->f_mode & FMODE_WRITE);
 }
 
-static int get_exclude(Sg_device *sdp)
-{
-	unsigned long flags;
-	int ret;
-
-	spin_lock_irqsave(&sg_open_exclusive_lock, flags);
-	ret = sdp->exclude;
-	spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);
-	return ret;
-}
-
-static int set_exclude(Sg_device *sdp, char val)
+static int
+open_wait(Sg_device *sdp, int flags)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&sg_open_exclusive_lock, flags);
-	sdp->exclude = val;
-	spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);
-	return val;
-}
+	int retval = 0;
 
-static int sfds_list_empty(Sg_device *sdp)
-{
-	unsigned long flags;
-	int ret;
+	if (flags & O_EXCL) {
+		while (sdp->open_cnt > 0) {
+			mutex_unlock(&sdp->open_rel_lock);
+			retval = wait_event_interruptible(sdp->open_wait,
+					(atomic_read(&sdp->detaching) ||
+					 !sdp->open_cnt));
+			mutex_lock(&sdp->open_rel_lock);
+
+			if (retval) /* -ERESTARTSYS */
+				return retval;
+			if (atomic_read(&sdp->detaching))
+				return -ENODEV;
+		}
+	} else {
+		while (sdp->exclude) {
+			mutex_unlock(&sdp->open_rel_lock);
+			retval = wait_event_interruptible(sdp->open_wait,
+					(atomic_read(&sdp->detaching) ||
+					 !sdp->exclude));
+			mutex_lock(&sdp->open_rel_lock);
+
+			if (retval) /* -ERESTARTSYS */
+				return retval;
+			if (atomic_read(&sdp->detaching))
+				return -ENODEV;
+		}
+	}
 
-	read_lock_irqsave(&sg_index_lock, flags);
-	ret = list_empty(&sdp->sfds);
-	read_unlock_irqrestore(&sg_index_lock, flags);
-	return ret;
+	return retval;
 }
 
+/* Returns 0 on success, else a negated errno value */
 static int
 sg_open(struct inode *inode, struct file *filp)
 {
@@ -269,17 +273,15 @@ sg_open(struct inode *inode, struct file *filp)
 	struct request_queue *q;
 	Sg_device *sdp;
 	Sg_fd *sfp;
-	int res;
 	int retval;
 
 	nonseekable_open(inode, filp);
 	SCSI_LOG_TIMEOUT(3, printk("sg_open: dev=%d, flags=0x%x\n", dev, flags));
+	if ((flags & O_EXCL) && (O_RDONLY == (flags & O_ACCMODE)))
+		return -EPERM; /* Can't lock it with read only access */
 	sdp = sg_get_dev(dev);
-	if (IS_ERR(sdp)) {
-		retval = PTR_ERR(sdp);
-		sdp = NULL;
-		goto sg_put;
-	}
+	if (IS_ERR(sdp))
+		return PTR_ERR(sdp);
 
 	/* This driver's module count bumped by fops_get in <linux/fs.h> */
 	/* Prevent the device driver from vanishing while we sleep */
@@ -291,6 +293,9 @@ sg_open(struct inode *inode, struct file *filp)
 	if (retval)
 		goto sdp_put;
 
+	/* scsi_block_when_processing_errors() may block so bypass
+	 * check if O_NONBLOCK. Permits SCSI commands to be issued
+	 * during error recovery. Tread carefully. */
 	if (!((flags & O_NONBLOCK) ||
 	      scsi_block_when_processing_errors(sdp->device))) {
 		retval = -ENXIO;
@@ -298,65 +303,65 @@ sg_open(struct inode *inode, struct file *filp)
 		goto error_out;
 	}
 
-	if (flags & O_EXCL) {
-		if (O_RDONLY == (flags & O_ACCMODE)) {
-			retval = -EPERM; /* Can't lock it with read only access */
-			goto error_out;
-		}
-		if (!sfds_list_empty(sdp) && (flags & O_NONBLOCK)) {
-			retval = -EBUSY;
-			goto error_out;
-		}
-		res = wait_event_interruptible(sdp->o_excl_wait,
-					   ((!sfds_list_empty(sdp) || get_exclude(sdp)) ? 0 : set_exclude(sdp, 1)));
-		if (res) {
-			retval = res;	/* -ERESTARTSYS because signal hit process */
-			goto error_out;
-		}
-	} else if (get_exclude(sdp)) {	/* some other fd has an exclusive lock on dev */
-		if (flags & O_NONBLOCK) {
-			retval = -EBUSY;
-			goto error_out;
-		}
-		res = wait_event_interruptible(sdp->o_excl_wait, !get_exclude(sdp));
-		if (res) {
-			retval = res;	/* -ERESTARTSYS because signal hit process */
-			goto error_out;
+	mutex_lock(&sdp->open_rel_lock);
+	if (flags & O_NONBLOCK) {
+		if (flags & O_EXCL) {
+			if (sdp->open_cnt > 0) {
+				retval = -EBUSY;
+				goto error_mutex_locked;
+			}
+		} else {
+			if (sdp->exclude) {
+				retval = -EBUSY;
+				goto error_mutex_locked;
+			}
 		}
+	} else {
+		retval = open_wait(sdp, flags);
+		if (retval) /* -ERESTARTSYS or -ENODEV */
+			goto error_mutex_locked;
 	}
-	if (sdp->detached) {
-		retval = -ENODEV;
-		goto error_out;
-	}
-	if (sfds_list_empty(sdp)) {	/* no existing opens on this device */
+
+	/* N.B. at this point we are holding the open_rel_lock */
+	if (flags & O_EXCL)
+		sdp->exclude = true;
+
+	if (sdp->open_cnt < 1) {  /* no existing opens */
 		sdp->sgdebug = 0;
 		q = sdp->device->request_queue;
 		sdp->sg_tablesize = queue_max_segments(q);
 	}
-	if ((sfp = sg_add_sfp(sdp, dev)))
-		filp->private_data = sfp;
-	else {
-		if (flags & O_EXCL) {
-			set_exclude(sdp, 0);	/* undo if error */
-			wake_up_interruptible(&sdp->o_excl_wait);
-		}
-		retval = -ENOMEM;
-		goto error_out;
+	sfp = sg_add_sfp(sdp, dev);
+	if (IS_ERR(sfp)) {
+		retval = PTR_ERR(sfp);
+		goto out_undo;
 	}
+
+	filp->private_data = sfp;
+	sdp->open_cnt++;
+	mutex_unlock(&sdp->open_rel_lock);
+
 	retval = 0;
-error_out:
-	if (retval) {
-		scsi_autopm_put_device(sdp->device);
-sdp_put:
-		scsi_device_put(sdp->device);
-	}
 sg_put:
-	if (sdp)
-		sg_put_dev(sdp);
+	kref_put(&sdp->d_ref, sg_device_destroy);
 	return retval;
+
+out_undo:
+	if (flags & O_EXCL) {
+		sdp->exclude = false;   /* undo if error */
+		wake_up_interruptible(&sdp->open_wait);
+	}
+error_mutex_locked:
+	mutex_unlock(&sdp->open_rel_lock);
+error_out:
+	scsi_autopm_put_device(sdp->device);
+sdp_put:
+	scsi_device_put(sdp->device);
+	goto sg_put;
 }
 
-/* Following function was formerly called 'sg_close' */
+/* Release resources associated with a successful sg_open()
+ * Returns 0 on success, else a negated errno value */
 static int
 sg_release(struct inode *inode, struct file *filp)
 {
@@ -367,11 +372,20 @@ sg_release(struct inode *inode, struct file *filp)
 		return -ENXIO;
 	SCSI_LOG_TIMEOUT(3, printk("sg_release: %s\n", sdp->disk->disk_name));
 
-	set_exclude(sdp, 0);
-	wake_up_interruptible(&sdp->o_excl_wait);
-
+	mutex_lock(&sdp->open_rel_lock);
 	scsi_autopm_put_device(sdp->device);
 	kref_put(&sfp->f_ref, sg_remove_sfp);
+	sdp->open_cnt--;
+
+	/* possibly many open()s waiting on exlude clearing, start many;
+	 * only open(O_EXCL)s wait on 0==open_cnt so only start one */
+	if (sdp->exclude) {
+		sdp->exclude = false;
+		wake_up_interruptible_all(&sdp->open_wait);
+	} else if (0 == sdp->open_cnt) {
+		wake_up_interruptible(&sdp->open_wait);
+	}
+	mutex_unlock(&sdp->open_rel_lock);
 	return 0;
 }
 
@@ -423,7 +437,7 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos)
 	}
 	srp = sg_get_rq_mark(sfp, req_pack_id);
 	if (!srp) {		/* now wait on packet to arrive */
-		if (sdp->detached) {
+		if (atomic_read(&sdp->detaching)) {
 			retval = -ENODEV;
 			goto free_old_hdr;
 		}
@@ -432,9 +446,9 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos)
 			goto free_old_hdr;
 		}
 		retval = wait_event_interruptible(sfp->read_wait,
-			(sdp->detached ||
+			(atomic_read(&sdp->detaching) ||
 			(srp = sg_get_rq_mark(sfp, req_pack_id))));
-		if (sdp->detached) {
+		if (atomic_read(&sdp->detaching)) {
 			retval = -ENODEV;
 			goto free_old_hdr;
 		}
@@ -576,7 +590,7 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
 		return -ENXIO;
 	SCSI_LOG_TIMEOUT(3, printk("sg_write: %s, count=%d\n",
 				   sdp->disk->disk_name, (int) count));
-	if (sdp->detached)
+	if (atomic_read(&sdp->detaching))
 		return -ENODEV;
 	if (!((filp->f_flags & O_NONBLOCK) ||
 	      scsi_block_when_processing_errors(sdp->device)))
@@ -762,7 +776,7 @@ sg_common_write(Sg_fd * sfp, Sg_request * srp,
 		sg_finish_rem_req(srp);
 		return k;	/* probably out of space --> ENOMEM */
 	}
-	if (sdp->detached) {
+	if (atomic_read(&sdp->detaching)) {
 		if (srp->bio)
 			blk_end_request_all(srp->rq, -EIO);
 		sg_finish_rem_req(srp);
@@ -838,7 +852,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 
 	switch (cmd_in) {
 	case SG_IO:
-		if (sdp->detached)
+		if (atomic_read(&sdp->detaching))
 			return -ENODEV;
 		if (!scsi_block_when_processing_errors(sdp->device))
 			return -ENXIO;
@@ -849,8 +863,8 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 		if (result < 0)
 			return result;
 		result = wait_event_interruptible(sfp->read_wait,
-			(srp_done(sfp, srp) || sdp->detached));
-		if (sdp->detached)
+			(srp_done(sfp, srp) || atomic_read(&sdp->detaching)));
+		if (atomic_read(&sdp->detaching))
 			return -ENODEV;
 		write_lock_irq(&sfp->rq_list_lock);
 		if (srp->done) {
@@ -889,7 +903,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 				sg_build_reserve(sfp, val);
 			}
 		} else {
-			if (sdp->detached)
+			if (atomic_read(&sdp->detaching))
 				return -ENODEV;
 			sfp->low_dma = sdp->device->host->unchecked_isa_dma;
 		}
@@ -902,7 +916,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 		else {
 			sg_scsi_id_t __user *sg_idp = p;
 
-			if (sdp->detached)
+			if (atomic_read(&sdp->detaching))
 				return -ENODEV;
 			__put_user((int) sdp->device->host->host_no,
 				   &sg_idp->host_no);
@@ -1044,11 +1058,11 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 			return result;
 		}
 	case SG_EMULATED_HOST:
-		if (sdp->detached)
+		if (atomic_read(&sdp->detaching))
 			return -ENODEV;
 		return put_user(sdp->device->host->hostt->emulated, ip);
 	case SG_SCSI_RESET:
-		if (sdp->detached)
+		if (atomic_read(&sdp->detaching))
 			return -ENODEV;
 		if (filp->f_flags & O_NONBLOCK) {
 			if (scsi_host_in_recovery(sdp->device->host))
@@ -1081,7 +1095,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 		return (scsi_reset_provider(sdp->device, val) ==
 			SUCCESS) ? 0 : -EIO;
 	case SCSI_IOCTL_SEND_COMMAND:
-		if (sdp->detached)
+		if (atomic_read(&sdp->detaching))
 			return -ENODEV;
 		if (read_only) {
 			unsigned char opcode = WRITE_6;
@@ -1103,7 +1117,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 	case SCSI_IOCTL_GET_BUS_NUMBER:
 	case SCSI_IOCTL_PROBE_HOST:
 	case SG_GET_TRANSFORM:
-		if (sdp->detached)
+		if (atomic_read(&sdp->detaching))
 			return -ENODEV;
 		return scsi_ioctl(sdp->device, cmd_in, p);
 	case BLKSECTGET:
@@ -1177,7 +1191,7 @@ sg_poll(struct file *filp, poll_table * wait)
 	}
 	read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
 
-	if (sdp->detached)
+	if (atomic_read(&sdp->detaching))
 		res |= POLLHUP;
 	else if (!sfp->cmd_q) {
 		if (0 == count)
@@ -1276,7 +1290,8 @@ sg_mmap(struct file *filp, struct vm_area_struct *vma)
 	return 0;
 }
 
-static void sg_rq_end_io_usercontext(struct work_struct *work)
+static void
+sg_rq_end_io_usercontext(struct work_struct *work)
 {
 	struct sg_request *srp = container_of(work, struct sg_request, ew.work);
 	struct sg_fd *sfp = srp->parentfp;
@@ -1289,7 +1304,8 @@ static void sg_rq_end_io_usercontext(struct work_struct *work)
  * This function is a "bottom half" handler that is called by the mid
  * level when a command is completed (or has failed).
  */
-static void sg_rq_end_io(struct request *rq, int uptodate)
+static void
+sg_rq_end_io(struct request *rq, int uptodate)
 {
 	struct sg_request *srp = rq->end_io_data;
 	Sg_device *sdp;
@@ -1307,8 +1323,8 @@ static void sg_rq_end_io(struct request *rq, int uptodate)
 		return;
 
 	sdp = sfp->parentdp;
-	if (unlikely(sdp->detached))
-		printk(KERN_INFO "sg_rq_end_io: device detached\n");
+	if (unlikely(atomic_read(&sdp->detaching)))
+		pr_info("%s: device detaching\n", __func__);
 
 	sense = rq->sense;
 	result = rq->errors;
@@ -1331,7 +1347,7 @@ static void sg_rq_end_io(struct request *rq, int uptodate)
 		if ((sdp->sgdebug > 0) &&
 		    ((CHECK_CONDITION == srp->header.masked_status) ||
 		     (COMMAND_TERMINATED == srp->header.masked_status)))
-			__scsi_print_sense("sg_cmd_done", sense,
+			__scsi_print_sense(__func__, sense,
 					   SCSI_SENSE_BUFFERSIZE);
 
 		/* Following if statement is a patch supplied by Eric Youngdale */
@@ -1390,7 +1406,8 @@ static struct class *sg_sysfs_class;
 
 static int sg_sysfs_valid = 0;
 
-static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
+static Sg_device *
+sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
 {
 	struct request_queue *q = scsidp->request_queue;
 	Sg_device *sdp;
@@ -1400,7 +1417,8 @@ static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
 
 	sdp = kzalloc(sizeof(Sg_device), GFP_KERNEL);
 	if (!sdp) {
-		printk(KERN_WARNING "kmalloc Sg_device failure\n");
+		sdev_printk(KERN_WARNING, scsidp, "%s: kmalloc Sg_device "
+			    "failure\n", __func__);
 		return ERR_PTR(-ENOMEM);
 	}
 
@@ -1415,8 +1433,9 @@ static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
 				    scsidp->type, SG_MAX_DEVS - 1);
 			error = -ENODEV;
 		} else {
-			printk(KERN_WARNING
-			       "idr allocation Sg_device failure: %d\n", error);
+			sdev_printk(KERN_WARNING, scsidp, "%s: idr "
+				    "allocation Sg_device failure: %d\n",
+				    __func__, error);
 		}
 		goto out_unlock;
 	}
@@ -1427,8 +1446,11 @@ static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
 	disk->first_minor = k;
 	sdp->disk = disk;
 	sdp->device = scsidp;
+	mutex_init(&sdp->open_rel_lock);
 	INIT_LIST_HEAD(&sdp->sfds);
-	init_waitqueue_head(&sdp->o_excl_wait);
+	init_waitqueue_head(&sdp->open_wait);
+	atomic_set(&sdp->detaching, 0);
+	rwlock_init(&sdp->sfd_lock);
 	sdp->sg_tablesize = queue_max_segments(q);
 	sdp->index = k;
 	kref_init(&sdp->d_ref);
@@ -1446,7 +1468,7 @@ out_unlock:
 }
 
 static int
-sg_add(struct device *cl_dev, struct class_interface *cl_intf)
+sg_add_device(struct device *cl_dev, struct class_interface *cl_intf)
 {
 	struct scsi_device *scsidp = to_scsi_device(cl_dev->parent);
 	struct gendisk *disk;
@@ -1457,7 +1479,7 @@ sg_add(struct device *cl_dev, struct class_interface *cl_intf)
 
 	disk = alloc_disk(1);
 	if (!disk) {
-		printk(KERN_WARNING "alloc_disk failed\n");
+		pr_warn("%s: alloc_disk failed\n", __func__);
 		return -ENOMEM;
 	}
 	disk->major = SCSI_GENERIC_MAJOR;
@@ -1465,7 +1487,7 @@ sg_add(struct device *cl_dev, struct class_interface *cl_intf)
 	error = -ENOMEM;
 	cdev = cdev_alloc();
 	if (!cdev) {
-		printk(KERN_WARNING "cdev_alloc failed\n");
+		pr_warn("%s: cdev_alloc failed\n", __func__);
 		goto out;
 	}
 	cdev->owner = THIS_MODULE;
@@ -1473,7 +1495,7 @@ sg_add(struct device *cl_dev, struct class_interface *cl_intf)
 
 	sdp = sg_alloc(disk, scsidp);
 	if (IS_ERR(sdp)) {
-		printk(KERN_WARNING "sg_alloc failed\n");
+		pr_warn("%s: sg_alloc failed\n", __func__);
 		error = PTR_ERR(sdp);
 		goto out;
 	}
@@ -1491,22 +1513,20 @@ sg_add(struct device *cl_dev, struct class_interface *cl_intf)
 						      sdp->index),
 						sdp, "%s", disk->disk_name);
 		if (IS_ERR(sg_class_member)) {
-			printk(KERN_ERR "sg_add: "
-			       "device_create failed\n");
+			pr_err("%s: device_create failed\n", __func__);
 			error = PTR_ERR(sg_class_member);
 			goto cdev_add_err;
 		}
 		error = sysfs_create_link(&scsidp->sdev_gendev.kobj,
 					  &sg_class_member->kobj, "generic");
 		if (error)
-			printk(KERN_ERR "sg_add: unable to make symlink "
-					"'generic' back to sg%d\n", sdp->index);
+			pr_err("%s: unable to make symlink 'generic' back "
+			       "to sg%d\n", __func__, sdp->index);
 	} else
-		printk(KERN_WARNING "sg_add: sg_sys Invalid\n");
+		pr_warn("%s: sg_sys Invalid\n", __func__);
 
-	sdev_printk(KERN_NOTICE, scsidp,
-		    "Attached scsi generic sg%d type %d\n", sdp->index,
-		    scsidp->type);
+	sdev_printk(KERN_NOTICE, scsidp, "Attached scsi generic sg%d "
+		    "type %d\n", sdp->index, scsidp->type);
 
 	dev_set_drvdata(cl_dev, sdp);
 
@@ -1525,7 +1545,8 @@ out:
 	return error;
 }
 
-static void sg_device_destroy(struct kref *kref)
+static void
+sg_device_destroy(struct kref *kref)
 {
 	struct sg_device *sdp = container_of(kref, struct sg_device, d_ref);
 	unsigned long flags;
@@ -1547,33 +1568,39 @@ static void sg_device_destroy(struct kref *kref)
 	kfree(sdp);
 }
 
-static void sg_remove(struct device *cl_dev, struct class_interface *cl_intf)
+static void
+sg_remove_device(struct device *cl_dev, struct class_interface *cl_intf)
 {
 	struct scsi_device *scsidp = to_scsi_device(cl_dev->parent);
 	Sg_device *sdp = dev_get_drvdata(cl_dev);
 	unsigned long iflags;
 	Sg_fd *sfp;
+	int val;
 
-	if (!sdp || sdp->detached)
+	if (!sdp)
 		return;
+	/* want sdp->detaching non-zero as soon as possible */
+	val = atomic_inc_return(&sdp->detaching);
+	if (val > 1)
+		return; /* only want to do following once per device */
 
-	SCSI_LOG_TIMEOUT(3, printk("sg_remove: %s\n", sdp->disk->disk_name));
+	SCSI_LOG_TIMEOUT(3, printk("%s: %s\n", __func__,
+			 sdp->disk->disk_name));
 
-	/* Need a write lock to set sdp->detached. */
-	write_lock_irqsave(&sg_index_lock, iflags);
-	sdp->detached = 1;
+	read_lock_irqsave(&sdp->sfd_lock, iflags);
 	list_for_each_entry(sfp, &sdp->sfds, sfd_siblings) {
-		wake_up_interruptible(&sfp->read_wait);
+		wake_up_interruptible_all(&sfp->read_wait);
 		kill_fasync(&sfp->async_qp, SIGPOLL, POLL_HUP);
 	}
-	write_unlock_irqrestore(&sg_index_lock, iflags);
+	wake_up_interruptible_all(&sdp->open_wait);
+	read_unlock_irqrestore(&sdp->sfd_lock, iflags);
 
 	sysfs_remove_link(&scsidp->sdev_gendev.kobj, "generic");
 	device_destroy(sg_sysfs_class, MKDEV(SCSI_GENERIC_MAJOR, sdp->index));
 	cdev_del(sdp->cdev);
 	sdp->cdev = NULL;
 
-	sg_put_dev(sdp);
+	kref_put(&sdp->d_ref, sg_device_destroy);
 }
 
 module_param_named(scatter_elem_sz, scatter_elem_sz, int, S_IRUGO | S_IWUSR);
@@ -1643,7 +1670,8 @@ exit_sg(void)
 	idr_destroy(&sg_index_idr);
 }
 
-static int sg_start_req(Sg_request *srp, unsigned char *cmd)
+static int
+sg_start_req(Sg_request *srp, unsigned char *cmd)
 {
 	int res;
 	struct request *rq;
@@ -1750,7 +1778,8 @@ static int sg_start_req(Sg_request *srp, unsigned char *cmd)
 	return res;
 }
 
-static int sg_finish_rem_req(Sg_request * srp)
+static int
+sg_finish_rem_req(Sg_request *srp)
 {
 	int ret = 0;
 
@@ -2089,7 +2118,7 @@ sg_add_sfp(Sg_device * sdp, int dev)
 
 	sfp = kzalloc(sizeof(*sfp), GFP_ATOMIC | __GFP_NOWARN);
 	if (!sfp)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	init_waitqueue_head(&sfp->read_wait);
 	rwlock_init(&sfp->rq_list_lock);
@@ -2103,9 +2132,13 @@ sg_add_sfp(Sg_device * sdp, int dev)
 	sfp->cmd_q = SG_DEF_COMMAND_Q;
 	sfp->keep_orphan = SG_DEF_KEEP_ORPHAN;
 	sfp->parentdp = sdp;
-	write_lock_irqsave(&sg_index_lock, iflags);
+	write_lock_irqsave(&sdp->sfd_lock, iflags);
+	if (atomic_read(&sdp->detaching)) {
+		write_unlock_irqrestore(&sdp->sfd_lock, iflags);
+		return ERR_PTR(-ENODEV);
+	}
 	list_add_tail(&sfp->sfd_siblings, &sdp->sfds);
-	write_unlock_irqrestore(&sg_index_lock, iflags);
+	write_unlock_irqrestore(&sdp->sfd_lock, iflags);
 	SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: sfp=0x%p\n", sfp));
 	if (unlikely(sg_big_buff != def_reserved_size))
 		sg_big_buff = def_reserved_size;
@@ -2121,7 +2154,8 @@ sg_add_sfp(Sg_device * sdp, int dev)
 	return sfp;
 }
 
-static void sg_remove_sfp_usercontext(struct work_struct *work)
+static void
+sg_remove_sfp_usercontext(struct work_struct *work)
 {
 	struct sg_fd *sfp = container_of(work, struct sg_fd, ew.work);
 	struct sg_device *sdp = sfp->parentdp;
@@ -2145,20 +2179,20 @@ static void sg_remove_sfp_usercontext(struct work_struct *work)
 	kfree(sfp);
 
 	scsi_device_put(sdp->device);
-	sg_put_dev(sdp);
+	kref_put(&sdp->d_ref, sg_device_destroy);
 	module_put(THIS_MODULE);
 }
 
-static void sg_remove_sfp(struct kref *kref)
+static void
+sg_remove_sfp(struct kref *kref)
 {
 	struct sg_fd *sfp = container_of(kref, struct sg_fd, f_ref);
 	struct sg_device *sdp = sfp->parentdp;
 	unsigned long iflags;
 
-	write_lock_irqsave(&sg_index_lock, iflags);
+	write_lock_irqsave(&sdp->sfd_lock, iflags);
 	list_del(&sfp->sfd_siblings);
-	write_unlock_irqrestore(&sg_index_lock, iflags);
-	wake_up_interruptible(&sdp->o_excl_wait);
+	write_unlock_irqrestore(&sdp->sfd_lock, iflags);
 
 	INIT_WORK(&sfp->ew.work, sg_remove_sfp_usercontext);
 	schedule_work(&sfp->ew.work);
@@ -2209,7 +2243,8 @@ static Sg_device *sg_lookup_dev(int dev)
 	return idr_find(&sg_index_idr, dev);
 }
 
-static Sg_device *sg_get_dev(int dev)
+static Sg_device *
+sg_get_dev(int dev)
 {
 	struct sg_device *sdp;
 	unsigned long flags;
@@ -2218,8 +2253,8 @@ static Sg_device *sg_get_dev(int dev)
 	sdp = sg_lookup_dev(dev);
 	if (!sdp)
 		sdp = ERR_PTR(-ENXIO);
-	else if (sdp->detached) {
-		/* If sdp->detached, then the refcount may already be 0, in
+	else if (atomic_read(&sdp->detaching)) {
+		/* If sdp->detaching, then the refcount may already be 0, in
 		 * which case it would be a bug to do kref_get().
 		 */
 		sdp = ERR_PTR(-ENODEV);
@@ -2230,11 +2265,6 @@ static Sg_device *sg_get_dev(int dev)
 	return sdp;
 }
 
-static void sg_put_dev(struct sg_device *sdp)
-{
-	kref_put(&sdp->d_ref, sg_device_destroy);
-}
-
 #ifdef CONFIG_SCSI_PROC_FS
 
 static struct proc_dir_entry *sg_proc_sgp = NULL;
@@ -2451,8 +2481,7 @@ static int sg_proc_single_open_version(struct inode *inode, struct file *file)
 
 static int sg_proc_seq_show_devhdr(struct seq_file *s, void *v)
 {
-	seq_printf(s, "host\tchan\tid\tlun\ttype\topens\tqdepth\tbusy\t"
-		   "online\n");
+	seq_puts(s, "host\tchan\tid\tlun\ttype\topens\tqdepth\tbusy\tonline\n");
 	return 0;
 }
 
@@ -2508,7 +2537,11 @@ static int sg_proc_seq_show_dev(struct seq_file *s, void *v)
 
 	read_lock_irqsave(&sg_index_lock, iflags);
 	sdp = it ? sg_lookup_dev(it->index) : NULL;
-	if (sdp && (scsidp = sdp->device) && (!sdp->detached))
+	if ((NULL == sdp) || (NULL == sdp->device) ||
+	    (atomic_read(&sdp->detaching)))
+		seq_puts(s, "-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\n");
+	else {
+		scsidp = sdp->device;
 		seq_printf(s, "%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d\n",
 			      scsidp->host->host_no, scsidp->channel,
 			      scsidp->id, scsidp->lun, (int) scsidp->type,
@@ -2516,8 +2549,7 @@ static int sg_proc_seq_show_dev(struct seq_file *s, void *v)
 			      (int) scsidp->queue_depth,
 			      (int) scsidp->device_busy,
 			      (int) scsi_device_online(scsidp));
-	else
-		seq_printf(s, "-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\n");
+	}
 	read_unlock_irqrestore(&sg_index_lock, iflags);
 	return 0;
 }
@@ -2536,11 +2568,12 @@ static int sg_proc_seq_show_devstrs(struct seq_file *s, void *v)
 
 	read_lock_irqsave(&sg_index_lock, iflags);
 	sdp = it ? sg_lookup_dev(it->index) : NULL;
-	if (sdp && (scsidp = sdp->device) && (!sdp->detached))
+	scsidp = sdp ? sdp->device : NULL;
+	if (sdp && scsidp && (!atomic_read(&sdp->detaching)))
 		seq_printf(s, "%8.8s\t%16.16s\t%4.4s\n",
 			   scsidp->vendor, scsidp->model, scsidp->rev);
 	else
-		seq_printf(s, "<no active device>\n");
+		seq_puts(s, "<no active device>\n");
 	read_unlock_irqrestore(&sg_index_lock, iflags);
 	return 0;
 }
@@ -2585,12 +2618,12 @@ static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
 				else
 					cp = "     ";
 			}
-			seq_printf(s, cp);
+			seq_puts(s, cp);
 			blen = srp->data.bufflen;
 			usg = srp->data.k_use_sg;
-			seq_printf(s, srp->done ? 
-				   ((1 == srp->done) ?  "rcv:" : "fin:")
-				   : "act:");
+			seq_puts(s, srp->done ?
+				 ((1 == srp->done) ?  "rcv:" : "fin:")
+				  : "act:");
 			seq_printf(s, " id=%d blen=%d",
 				   srp->header.pack_id, blen);
 			if (srp->done)
@@ -2606,7 +2639,7 @@ static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
 				   (int) srp->data.cmd_opcode);
 		}
 		if (0 == m)
-			seq_printf(s, "     No requests active\n");
+			seq_puts(s, "     No requests active\n");
 		read_unlock(&fp->rq_list_lock);
 	}
 }
@@ -2622,31 +2655,34 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v)
 	Sg_device *sdp;
 	unsigned long iflags;
 
-	if (it && (0 == it->index)) {
-		seq_printf(s, "max_active_device=%d(origin 1)\n",
-			   (int)it->max);
-		seq_printf(s, " def_reserved_size=%d\n", sg_big_buff);
-	}
+	if (it && (0 == it->index))
+		seq_printf(s, "max_active_device=%d  def_reserved_size=%d\n",
+			   (int)it->max, sg_big_buff);
 
 	read_lock_irqsave(&sg_index_lock, iflags);
 	sdp = it ? sg_lookup_dev(it->index) : NULL;
-	if (sdp && !list_empty(&sdp->sfds)) {
-		struct scsi_device *scsidp = sdp->device;
-
+	if (NULL == sdp)
+		goto skip;
+	read_lock(&sdp->sfd_lock);
+	if (!list_empty(&sdp->sfds)) {
 		seq_printf(s, " >>> device=%s ", sdp->disk->disk_name);
-		if (sdp->detached)
-			seq_printf(s, "detached pending close ");
-		else
-			seq_printf
-			    (s, "scsi%d chan=%d id=%d lun=%d   em=%d",
-			     scsidp->host->host_no,
-			     scsidp->channel, scsidp->id,
-			     scsidp->lun,
-			     scsidp->host->hostt->emulated);
-		seq_printf(s, " sg_tablesize=%d excl=%d\n",
-			   sdp->sg_tablesize, get_exclude(sdp));
+		if (atomic_read(&sdp->detaching))
+			seq_puts(s, "detaching pending close ");
+		else if (sdp->device) {
+			struct scsi_device *scsidp = sdp->device;
+
+			seq_printf(s, "%d:%d:%d:%d   em=%d",
+				   scsidp->host->host_no,
+				   scsidp->channel, scsidp->id,
+				   scsidp->lun,
+				   scsidp->host->hostt->emulated);
+		}
+		seq_printf(s, " sg_tablesize=%d excl=%d open_cnt=%d\n",
+			   sdp->sg_tablesize, sdp->exclude, sdp->open_cnt);
 		sg_proc_debug_helper(s, sdp);
 	}
+	read_unlock(&sdp->sfd_lock);
+skip:
 	read_unlock_irqrestore(&sg_index_lock, iflags);
 	return 0;
 }