[PATCH] update sr to use kref and fix open/release race

James Bottomley
2004-04-09T13:51:27Z

The previous patch actually didn't null out the disk->private_data
pointer in it's release mechanism. This does that and converts sr to
use the lightweight kref object instead of a kobject.

James

===== drivers/scsi/sr.c 1.104 vs edited =====
--- 1.104/drivers/scsi/sr.c Thu Apr 8 08:39:12 2004
+++ edited/drivers/scsi/sr.c Thu Apr 8 16:33:11 2004
@@ -86,6 +86,7 @@

static unsigned long sr_index_bits[SR_DISKS / BITS_PER_LONG];
static spinlock_t sr_index_lock = SPIN_LOCK_UNLOCKED;
+static DECLARE_MUTEX(sr_ref_sem);

static int sr_open(struct cdrom_device_info *, int);
static void sr_release(struct cdrom_device_info *);
@@ -119,20 +120,35 @@
.release = sr_kobject_release,
};

+static inline struct scsi_cd *scsi_cd(struct gendisk *disk)
+{
+ return container_of(disk->private_data, struct scsi_cd, driver);
+}
+
/*
* The get and put routines for the struct scsi_cd. Note this entity
* has a scsi_device pointer and owns a reference to this.
*/
-static inline int scsi_cd_get(struct scsi_cd *cd)
+static inline struct scsi_cd *scsi_cd_get(struct gendisk *disk)
{
+ struct scsi_cd *cd = NULL;
+
+ down(&sr_ref_sem);
+ if (disk->private_data == NULL)
+ goto out;
+ cd = scsi_cd(disk);
if (!kobject_get(&cd->kobj))
- return -ENODEV;
- return 0;
+ cd = NULL;
+ out:
+ up(&sr_ref_sem);
+ return cd;
}

static inline void scsi_cd_put(struct scsi_cd *cd)
{
+ down(&sr_ref_sem);
kobject_put(&cd->kobj);
+ up(&sr_ref_sem);
}

/*
@@ -187,11 +203,6 @@
return retval;
}

-static inline struct scsi_cd *scsi_cd(struct gendisk *disk)
-{
- return container_of(disk->private_data, struct scsi_cd, driver);
-}
-
/*
* rw_intr is the interrupt routine for the device driver.
*
@@ -440,8 +451,17 @@

static int sr_block_open(struct inode *inode, struct file *file)
{
+ struct gendisk *disk = inode->i_bdev->bd_disk;
struct scsi_cd *cd = scsi_cd(inode->i_bdev->bd_disk);
- return cdrom_open(&cd->cdi, inode, file);
+ int ret = 0;
+
+ if(!(cd = scsi_cd_get(disk)))
+ return -ENXIO;
+
+ if((ret = cdrom_open(&cd->cdi, inode, file)) != 0)
+ scsi_cd_put(cd);
+
+ return ret;
}

static int sr_block_release(struct inode *inode, struct file *file)
@@ -496,10 +516,6 @@
struct scsi_device *sdev = cd->device;
int retval;

- retval = scsi_cd_get(cd);
- if (retval)
- return retval;
-
/*
* If the device is in error recovery, wait until it is done.
* If the device is offline, then disallow any access to it.