[SCSI] sg: protect sdp->exclude
Changes since v1: set_exclude now returns the new value, which gets rid of the comma expression and the operator precedence bug. Thanks to Douglas for spotting it. sdp->exclude was previously protected by the BKL. The sg_mutex, which replaced the BKL, only semi-protected it, as it was missing from sg_release() and sg_proc_seq_show_debug(). Take an explicit spinlock for it. Signed-off-by: Joern Engel <joern@logfs.org> Acked-by: Douglas Gilbert <dgilbert@interlog.com> Signed-off-by: James Bottomley <JBottomley@Parallels.com>
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@ -105,6 +105,7 @@ static int sg_add(struct device *, struct class_interface *);
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static void sg_remove(struct device *, struct class_interface *);
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static DEFINE_MUTEX(sg_mutex);
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static DEFINE_SPINLOCK(sg_open_exclusive_lock);
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static DEFINE_IDR(sg_index_idr);
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static DEFINE_RWLOCK(sg_index_lock); /* Also used to lock
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@ -173,7 +174,8 @@ typedef struct sg_device { /* holds the state of each scsi generic device */
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u32 index; /* device index number */
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struct list_head sfds;
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volatile char detached; /* 0->attached, 1->detached pending removal */
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volatile char exclude; /* opened for exclusive access */
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/* exclude protected by sg_open_exclusive_lock */
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char exclude; /* opened for exclusive access */
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char sgdebug; /* 0->off, 1->sense, 9->dump dev, 10-> all devs */
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struct gendisk *disk;
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struct cdev * cdev; /* char_dev [sysfs: /sys/cdev/major/sg<n>] */
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@ -221,6 +223,27 @@ static int sg_allow_access(struct file *filp, unsigned char *cmd)
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return blk_verify_command(cmd, filp->f_mode & FMODE_WRITE);
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}
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static int get_exclude(Sg_device *sdp)
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{
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unsigned long flags;
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int ret;
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spin_lock_irqsave(&sg_open_exclusive_lock, flags);
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ret = sdp->exclude;
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spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);
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return ret;
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}
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static int set_exclude(Sg_device *sdp, char val)
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{
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unsigned long flags;
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spin_lock_irqsave(&sg_open_exclusive_lock, flags);
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sdp->exclude = val;
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spin_unlock_irqrestore(&sg_open_exclusive_lock, flags);
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return val;
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}
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static int
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sg_open(struct inode *inode, struct file *filp)
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{
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@ -269,17 +292,17 @@ sg_open(struct inode *inode, struct file *filp)
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goto error_out;
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}
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res = wait_event_interruptible(sdp->o_excl_wait,
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((!list_empty(&sdp->sfds) || sdp->exclude) ? 0 : (sdp->exclude = 1)));
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((!list_empty(&sdp->sfds) || get_exclude(sdp)) ? 0 : set_exclude(sdp, 1)));
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if (res) {
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retval = res; /* -ERESTARTSYS because signal hit process */
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goto error_out;
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}
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} else if (sdp->exclude) { /* some other fd has an exclusive lock on dev */
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} else if (get_exclude(sdp)) { /* some other fd has an exclusive lock on dev */
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if (flags & O_NONBLOCK) {
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retval = -EBUSY;
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goto error_out;
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}
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res = wait_event_interruptible(sdp->o_excl_wait, !sdp->exclude);
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res = wait_event_interruptible(sdp->o_excl_wait, !get_exclude(sdp));
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if (res) {
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retval = res; /* -ERESTARTSYS because signal hit process */
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goto error_out;
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@ -298,7 +321,7 @@ sg_open(struct inode *inode, struct file *filp)
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filp->private_data = sfp;
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else {
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if (flags & O_EXCL) {
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sdp->exclude = 0; /* undo if error */
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set_exclude(sdp, 0); /* undo if error */
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wake_up_interruptible(&sdp->o_excl_wait);
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}
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retval = -ENOMEM;
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@ -329,7 +352,7 @@ sg_release(struct inode *inode, struct file *filp)
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return -ENXIO;
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SCSI_LOG_TIMEOUT(3, printk("sg_release: %s\n", sdp->disk->disk_name));
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sdp->exclude = 0;
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set_exclude(sdp, 0);
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wake_up_interruptible(&sdp->o_excl_wait);
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scsi_autopm_put_device(sdp->device);
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@ -2606,7 +2629,7 @@ static int sg_proc_seq_show_debug(struct seq_file *s, void *v)
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scsidp->lun,
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scsidp->host->hostt->emulated);
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seq_printf(s, " sg_tablesize=%d excl=%d\n",
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sdp->sg_tablesize, sdp->exclude);
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sdp->sg_tablesize, get_exclude(sdp));
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sg_proc_debug_helper(s, sdp);
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}
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read_unlock_irqrestore(&sg_index_lock, iflags);
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