1 files changed, 95 insertions, 81 deletions

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 5cbc4bb1b395..df5e961484e1 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -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))) {
-                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)) {
-                                retval = -EBUSY;
-                                goto error_out;
-                        }
-                } else {
-                        if (!down_read_trylock(&sdp->o_sem)) {
-                                retval = -EBUSY;
-                                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;
                 }
-        } 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;
@@ -2587,26 +2605,22 @@ 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)) {
-                        struct scsi_device *scsidp = sdp->device;
+        if (sdp && !list_empty(&sdp->sfds)) {
+                struct scsi_device *scsidp = sdp->device;
 
-                        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, sdp->exclude);
-                        sg_proc_debug_helper(s, sdp);
-                }
-                spin_unlock(&sdp->sfd_lock);
+                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));
+                sg_proc_debug_helper(s, sdp);
         }
         read_unlock_irqrestore(&sg_index_lock, iflags);
         return 0;