Commit 5d914a95 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi 

Pull SCSI fixes from James Bottomley:
 "This is a set of four patches that revert functionality introduced in
  the merge window to sg.  The locking changes turned out to introduce
  this bug:

      [  205.372901] [ BUG: lock held when returning to user space! ]
   [...]
      [  205.373285]  #0:  (&sdp->o_sem){.+.+..}, at: [<ffffffff8161e650>] sg_open+0x3a0/0x4d0

  The fix is large, so at this late stage we'd like to revert the
  functionality and start again in the next merge window"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  [SCSI] Revert "sg: use rwsem to solve race during exclusive open"
  [SCSI] Revert "sg: no need sg_open_exclusive_lock"
  [SCSI] Revert "sg: checking sdp->detached isn't protected when open"
  [SCSI] Revert "sg: push file descriptor list locking down to per-device locking"
parents 959f5854 065b4a2f

drivers/scsi/sg.c

+95 −81
Original line number Diff line number Diff line
@@ -105,8 +105,11 @@ static int scatter_elem_sz_prev = SG_SCATTER_SZ; 
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 DEFINE_IDR(sg_index_idr);

static DEFINE_RWLOCK(sg_index_lock);

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,
@@ -143,7 +146,8 @@ typedef struct sg_request { /* SG_MAX_QUEUE requests outstanding per file */ 
} Sg_request;



typedef struct sg_fd {		/* holds the state of a file descriptor */

	struct list_head sfd_siblings; /* protected by sfd_lock of device */

	/* sfd_siblings is protected by sg_index_lock */

	struct list_head sfd_siblings;

	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 */
@@ -166,12 +170,13 @@ 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 */

	int sg_tablesize;	/* adapter's max scatter-gather table size */

	u32 index;		/* device index number */

	spinlock_t sfd_lock;	/* protect file descriptor list for device */

	/* sfds is protected by sg_index_lock */

	struct list_head sfds;

	struct rw_semaphore o_sem;	/* exclude open should hold this rwsem */

	volatile char detached;	/* 0->attached, 1->detached pending removal */

	/* exclude protected by sg_open_exclusive_lock */

	char exclude;		/* opened for exclusive access */

	char sgdebug;		/* 0->off, 1->sense, 9->dump dev, 10-> all devs */

	struct gendisk *disk;
@@ -220,14 +225,35 @@ 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)

{

	unsigned long flags;



	spin_lock_irqsave(&sg_open_exclusive_lock, flags);

	sdp->exclude = val;

	spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);

	return val;

}



static int sfds_list_empty(Sg_device *sdp)

{

	unsigned long flags;

	int ret;



	spin_lock_irqsave(&sdp->sfd_lock, flags);

	read_lock_irqsave(&sg_index_lock, flags);

	ret = list_empty(&sdp->sfds);

	spin_unlock_irqrestore(&sdp->sfd_lock, flags);

	read_unlock_irqrestore(&sg_index_lock, flags);

	return ret;

}
@@ -239,6 +265,7 @@ 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);
@@ -267,52 +294,54 @@ sg_open(struct inode *inode, struct file *filp) 
		goto error_out;

	}



	if ((flags & O_EXCL) && (O_RDONLY == (flags & O_ACCMODE))) {

	if (flags & O_EXCL) {

		if (O_RDONLY == (flags & O_ACCMODE)) {

			retval = -EPERM; /* Can't lock it with read only access */

			goto error_out;

		}

	if (flags & O_NONBLOCK) {

		if (flags & O_EXCL) {

			if (!down_write_trylock(&sdp->o_sem)) {

		if (!sfds_list_empty(sdp) && (flags & O_NONBLOCK)) {

			retval = -EBUSY;

			goto error_out;

		}

		} else {

			if (!down_read_trylock(&sdp->o_sem)) {

		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;

		}

	} else {

		if (flags & O_EXCL)

			down_write(&sdp->o_sem);

		else

			down_read(&sdp->o_sem);

	}

	/* Since write lock is held, no need to check sfd_list */

	if (flags & O_EXCL)

		sdp->exclude = 1;	/* used by release lock */



	if (sdp->detached) {

		retval = -ENODEV;

		goto error_out;

	}

	if (sfds_list_empty(sdp)) {	/* no existing opens on this device */

		sdp->sgdebug = 0;

		q = sdp->device->request_queue;

		sdp->sg_tablesize = queue_max_segments(q);

	}

	sfp = sg_add_sfp(sdp, dev);

	if (!IS_ERR(sfp))

	if ((sfp = sg_add_sfp(sdp, dev)))

		filp->private_data = sfp;

		/* retval is already provably zero at this point because of the

		 * check after retval = scsi_autopm_get_device(sdp->device))

		 */

	else {

		retval = PTR_ERR(sfp);



		if (flags & O_EXCL) {

			sdp->exclude = 0;	/* undo if error */

			up_write(&sdp->o_sem);

		} else

			up_read(&sdp->o_sem);

			set_exclude(sdp, 0);	/* undo if error */

			wake_up_interruptible(&sdp->o_excl_wait);

		}

		retval = -ENOMEM;

		goto error_out;

	}

	retval = 0;

error_out:

	if (retval) {

		scsi_autopm_put_device(sdp->device);

sdp_put:

		scsi_device_put(sdp->device);
@@ -329,18 +358,13 @@ sg_release(struct inode *inode, struct file *filp) 
{

	Sg_device *sdp;

	Sg_fd *sfp;

	int excl;



	if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))

		return -ENXIO;

	SCSI_LOG_TIMEOUT(3, printk("sg_release: %s\n", sdp->disk->disk_name));



	excl = sdp->exclude;

	sdp->exclude = 0;

	if (excl)

		up_write(&sdp->o_sem);

	else

		up_read(&sdp->o_sem);

	set_exclude(sdp, 0);

	wake_up_interruptible(&sdp->o_excl_wait);



	scsi_autopm_put_device(sdp->device);

	kref_put(&sfp->f_ref, sg_remove_sfp);
@@ -1391,9 +1415,8 @@ static Sg_device *sg_alloc(struct gendisk *disk, struct scsi_device *scsidp) 
	disk->first_minor = k;

	sdp->disk = disk;

	sdp->device = scsidp;

	spin_lock_init(&sdp->sfd_lock);

	INIT_LIST_HEAD(&sdp->sfds);

	init_rwsem(&sdp->o_sem);

	init_waitqueue_head(&sdp->o_excl_wait);

	sdp->sg_tablesize = queue_max_segments(q);

	sdp->index = k;

	kref_init(&sdp->d_ref);
@@ -1526,13 +1549,11 @@ static void sg_remove(struct device *cl_dev, struct class_interface *cl_intf) 


	/* Need a write lock to set sdp->detached. */

	write_lock_irqsave(&sg_index_lock, iflags);

	spin_lock(&sdp->sfd_lock);

	sdp->detached = 1;

	list_for_each_entry(sfp, &sdp->sfds, sfd_siblings) {

		wake_up_interruptible(&sfp->read_wait);

		kill_fasync(&sfp->async_qp, SIGPOLL, POLL_HUP);

	}

	spin_unlock(&sdp->sfd_lock);

	write_unlock_irqrestore(&sg_index_lock, iflags);



	sysfs_remove_link(&scsidp->sdev_gendev.kobj, "generic");
@@ -2043,7 +2064,7 @@ sg_add_sfp(Sg_device * sdp, int dev) 


	sfp = kzalloc(sizeof(*sfp), GFP_ATOMIC | __GFP_NOWARN);

	if (!sfp)

		return ERR_PTR(-ENOMEM);

		return NULL;



	init_waitqueue_head(&sfp->read_wait);

	rwlock_init(&sfp->rq_list_lock);
@@ -2057,13 +2078,9 @@ 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;

	spin_lock_irqsave(&sdp->sfd_lock, iflags);

	if (sdp->detached) {

		spin_unlock_irqrestore(&sdp->sfd_lock, iflags);

		return ERR_PTR(-ENODEV);

	}

	write_lock_irqsave(&sg_index_lock, iflags);

	list_add_tail(&sfp->sfd_siblings, &sdp->sfds);

	spin_unlock_irqrestore(&sdp->sfd_lock, iflags);

	write_unlock_irqrestore(&sg_index_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;
@@ -2113,9 +2130,10 @@ static void sg_remove_sfp(struct kref *kref) 
	struct sg_device *sdp = sfp->parentdp;

	unsigned long iflags;



	spin_lock_irqsave(&sdp->sfd_lock, iflags);

	write_lock_irqsave(&sg_index_lock, iflags);

	list_del(&sfp->sfd_siblings);

	spin_unlock_irqrestore(&sdp->sfd_lock, iflags);

	write_unlock_irqrestore(&sg_index_lock, iflags);

	wake_up_interruptible(&sdp->o_excl_wait);



	INIT_WORK(&sfp->ew.work, sg_remove_sfp_usercontext);

	schedule_work(&sfp->ew.work);
@@ -2502,7 +2520,7 @@ static int sg_proc_seq_show_devstrs(struct seq_file *s, void *v) 
	return 0;

}



/* must be called while holding sg_index_lock and sfd_lock */

/* must be called while holding sg_index_lock */

static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)

{

	int k, m, new_interface, blen, usg;
@@ -2587,9 +2605,7 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v) 


	read_lock_irqsave(&sg_index_lock, iflags);

	sdp = it ? sg_lookup_dev(it->index) : NULL;

	if (sdp) {

		spin_lock(&sdp->sfd_lock);

		if (!list_empty(&sdp->sfds)) {

	if (sdp && !list_empty(&sdp->sfds)) {

		struct scsi_device *scsidp = sdp->device;



		seq_printf(s, " >>> device=%s ", sdp->disk->disk_name);
@@ -2603,11 +2619,9 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v) 
			     scsidp->lun,

			     scsidp->host->hostt->emulated);

		seq_printf(s, " sg_tablesize=%d excl=%d\n",

				   sdp->sg_tablesize, sdp->exclude);

			   sdp->sg_tablesize, get_exclude(sdp));

		sg_proc_debug_helper(s, sdp);

	}

		spin_unlock(&sdp->sfd_lock);

	}

	read_unlock_irqrestore(&sg_index_lock, iflags);

	return 0;

}

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