[patch 8/8] ide-scsi: add basic refcounting
From: Bartlomiej Zolnierkiewicz (bzolnier_at_elka.pw.edu.pl)
Date: 01/22/05
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Date: Sat, 22 Jan 2005 00:38:42 +0100 (CET) To: linux-ide@vger.kernel.org
* pointers to a SCSI host and a drive are added to idescsi_scsi_t
* pointer to the SCSI host is stored in disk->private_data
* ide_scsi_{get,put}() is used to {get,put} reference to the SCSI host
Unfortunately this is not complete fix for ->open() vs ->cleanup()
race, there are two TODO items left (as stated by FIXMEs):
* don't use drive->driver_data
* add driver's private struct gendisk [already DONE]
Last minute note: it seems we can't get rid of drive->driver_data
because of interactions between ide-scsi and IDE core (no surprise),
drive->driver_data should be set to NULL when SCSI host object is
being destroyed - callback from scsi_host_dev_release() is needed.
This will help in fixing another problem - for IDE we need to wait
until driver is really no longer using the device because we have more
than 1 driver for the same class of devices (ide-{cd,floppy,tape} vs
ide-scsi, also there is ide-default hack but it will die soon).
diff -Nru a/drivers/scsi/ide-scsi.c b/drivers/scsi/ide-scsi.c
--- a/drivers/scsi/ide-scsi.c 2005-01-21 23:41:42 +01:00
+++ b/drivers/scsi/ide-scsi.c 2005-01-21 23:41:42 +01:00
@@ -96,14 +96,39 @@
*/
#define IDESCSI_LOG_CMD 0 /* Log SCSI commands */
-typedef struct {
- ide_drive_t *drive;
+typedef struct ide_scsi_obj {
+ ide_drive_t *drive;
+ struct Scsi_Host *host;
+
idescsi_pc_t *pc; /* Current packet command */
unsigned long flags; /* Status/Action flags */
unsigned long transform; /* SCSI cmd translation layer */
unsigned long log; /* log flags */
} idescsi_scsi_t;
+static DECLARE_MUTEX(idescsi_ref_sem);
+
+#define ide_scsi_g(disk) ((disk)->private_data)
+
+static struct ide_scsi_obj *ide_scsi_get(struct gendisk *disk)
+{
+ struct ide_scsi_obj *scsi = NULL;
+
+ down(&idescsi_ref_sem);
+ scsi = ide_scsi_g(disk);
+ if (scsi)
+ scsi_host_get(scsi->host);
+ up(&idescsi_ref_sem);
+ return scsi;
+}
+
+static void ide_scsi_put(struct ide_scsi_obj *scsi)
+{
+ down(&idescsi_ref_sem);
+ scsi_host_put(scsi->host);
+ up(&idescsi_ref_sem);
+}
+
static inline idescsi_scsi_t *scsihost_to_idescsi(struct Scsi_Host *host)
{
return (idescsi_scsi_t*) (&host[1]);
@@ -693,16 +718,20 @@
static int idescsi_cleanup (ide_drive_t *drive)
{
struct Scsi_Host *scsihost = drive->driver_data;
+ struct gendisk *g = drive->disk;
if (ide_unregister_subdriver(drive))
return 1;
-
- /* FIXME?: Are these two statements necessary? */
+
+ /* FIXME: drive->driver_data shouldn't be used */
drive->driver_data = NULL;
- drive->disk->fops = ide_fops;
+ /* FIXME: add driver's private struct gendisk */
+ g->private_data = NULL;
+ g->fops = ide_fops;
scsi_remove_host(scsihost);
- scsi_host_put(scsihost);
+ ide_scsi_put(scsihost_to_idescsi(scsihost));
+
return 0;
}
@@ -739,15 +768,30 @@
static int idescsi_ide_open(struct inode *inode, struct file *filp)
{
- ide_drive_t *drive = inode->i_bdev->bd_disk->private_data;
+ struct gendisk *disk = inode->i_bdev->bd_disk;
+ struct ide_scsi_obj *scsi;
+ ide_drive_t *drive;
+
+ if (!(scsi = ide_scsi_get(disk)))
+ return -ENXIO;
+
+ drive = scsi->drive;
+
drive->usage++;
+
return 0;
}
static int idescsi_ide_release(struct inode *inode, struct file *filp)
{
- ide_drive_t *drive = inode->i_bdev->bd_disk->private_data;
+ struct gendisk *disk = inode->i_bdev->bd_disk;
+ struct ide_scsi_obj *scsi = ide_scsi_g(disk);
+ ide_drive_t *drive = scsi->drive;
+
drive->usage--;
+
+ ide_scsi_put(scsi);
+
return 0;
}
@@ -755,8 +799,8 @@
unsigned int cmd, unsigned long arg)
{
struct block_device *bdev = inode->i_bdev;
- ide_drive_t *drive = bdev->bd_disk->private_data;
- return generic_ide_ioctl(drive, file, bdev, cmd, arg);
+ struct ide_scsi_obj *scsi = ide_scsi_g(bdev->bd_disk);
+ return generic_ide_ioctl(scsi->drive, file, bdev, cmd, arg);
}
static struct block_device_operations idescsi_ops = {
@@ -1043,6 +1087,7 @@
{
idescsi_scsi_t *idescsi;
struct Scsi_Host *host;
+ struct gendisk *g = drive->disk;
static int warned;
int err;
@@ -1071,10 +1116,12 @@
drive->driver_data = host;
idescsi = scsihost_to_idescsi(host);
idescsi->drive = drive;
+ idescsi->host = host;
err = ide_register_subdriver(drive, &idescsi_driver);
if (!err) {
idescsi_setup (drive, idescsi);
- drive->disk->fops = &idescsi_ops;
+ g->fops = &idescsi_ops;
+ g->private_data = idescsi;
err = scsi_add_host(host, &drive->gendev);
if (!err) {
scsi_scan_host(host);
-
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- Previous message: Chris Wright: "Re: [Dev] Re: Kernel Panic with LTP on 2.6.11-rc1 (was Re: LTP Results for 2.6.x and 2.4.x)"
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