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Commit 1f962ebc authored by Vaughan Cao's avatar Vaughan Cao Committed by James Bottomley
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[SCSI] sg: push file descriptor list locking down to per-device locking 



Push file descriptor list locking down to per-device locking. Let sg_index_lock
only protect device lookup.
sdp->detached is also set and checked with this lock held.

Signed-off-by: default avatarVaughan Cao <vaughan.cao@oracle.com>
Acked-by: default avatarDouglas Gilbert <dgilbert@interlog.com>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent e32c9e63

drivers/scsi/sg.c

+34 −28
Original line number Diff line number Diff line
@@ -106,8 +106,7 @@ static int sg_add(struct device *, struct class_interface *); 
static void sg_remove(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 DEFINE_RWLOCK(sg_index_lock);



static struct class_interface sg_interface = {

	.add_dev	= sg_add,
@@ -144,8 +143,7 @@ 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 sfd_lock of device */

	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 */
@@ -170,7 +168,7 @@ typedef struct sg_device { /* holds the state of each scsi generic device */ 
	struct scsi_device *device;

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

	u32 index;		/* device index number */

	/* sfds is protected by sg_index_lock */

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

	struct list_head sfds;

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

	volatile char detached;	/* 0->attached, 1->detached pending removal */
@@ -227,9 +225,9 @@ static int sfds_list_empty(Sg_device *sdp) 
	unsigned long flags;

	int ret;



	read_lock_irqsave(&sg_index_lock, flags);

	spin_lock_irqsave(&sdp->sfd_lock, flags);

	ret = list_empty(&sdp->sfds);

	read_unlock_irqrestore(&sg_index_lock, flags);

	spin_unlock_irqrestore(&sdp->sfd_lock, flags);

	return ret;

}
@@ -1393,6 +1391,7 @@ 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);

	sdp->sg_tablesize = queue_max_segments(q);
@@ -1527,11 +1526,13 @@ 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");
@@ -2056,13 +2057,13 @@ 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);

	spin_lock_irqsave(&sdp->sfd_lock, iflags);

	if (sdp->detached) {

		write_unlock_irqrestore(&sg_index_lock, iflags);

		spin_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);

	spin_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;
@@ -2109,11 +2110,12 @@ static void sg_remove_sfp_usercontext(struct work_struct *work) 
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);

	spin_lock_irqsave(&sdp->sfd_lock, iflags);

	list_del(&sfp->sfd_siblings);

	write_unlock_irqrestore(&sg_index_lock, iflags);

	spin_unlock_irqrestore(&sdp->sfd_lock, iflags);



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

	schedule_work(&sfp->ew.work);
@@ -2500,7 +2502,7 @@ static int sg_proc_seq_show_devstrs(struct seq_file *s, void *v) 
	return 0;

}



/* must be called while holding sg_index_lock */

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

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

{

	int k, m, new_interface, blen, usg;
@@ -2585,7 +2587,9 @@ 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 && !list_empty(&sdp->sfds)) {

	if (sdp) {

		spin_lock(&sdp->sfd_lock);

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

			struct scsi_device *scsidp = sdp->device;



			seq_printf(s, " >>> device=%s ", sdp->disk->disk_name);
@@ -2602,6 +2606,8 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v) 
				   sdp->sg_tablesize, sdp->exclude);

			sg_proc_debug_helper(s, sdp);

		}

		spin_unlock(&sdp->sfd_lock);

	}

	read_unlock_irqrestore(&sg_index_lock, iflags);

	return 0;

}