Re: Problem with usb-storage and /dev/sd?

Willy Tarreau
2005-08-14T09:12:26Z

Hi Raul,

On Sun, Aug 14, 2005 at 09:32:57AM +0200, DervishD wrote:
> Hi Pete :)
>
> * Pete Zaitcev <zaitcev@redhat.com> dixit:
> > > A global unique ID won't work out to make all USB mass storage devices
> > > appear under a common mountpoint, especially if it is recreated while
> > > "formating" it.
> > That is correct, but not what Dervish wanted. He wanted to mount them
> > on separate pre-assigned mount points. If you want all of them to mount
> > on the same place, just use /dev/sda1!
>
> That's not possible. sd_mod will assign different devices for
> different USB gadgets, and that's my problem in the first case!. If I
> plug my USB-whatever, it gets assigned /dev/sda1 (for the first
> partition, I mean). If I unplug it and, after that, I plug any other
> USB device, it gets assigned /dev/sdb1, etc. Don't know if the
> culprit is usb-storage or sd_mod :? The problem is that I cannot know
> about which device was assigned (at least in 2.4.x) so I can modify
> fstab or even mount it.

I've been suffering from the same problem for a long time until I found
a patch from Erik Andersen which automatically unregisters the sd device
once you unplug the USB device. It has changed my life :-)

Here it is for 2.4. I even wonder why we would not put this into mainline,
since having orphan devices brings nothing but confusion.

Regards,
Willy

----

This patch has been in use locally for quite some time now and
makes working with USB and 1394 mass-storage devices in 2.4.x a
much less painful experience. When devices are plugged in, they
are automagically connected up to the scsi subsystem without the
need to rescan all scsi busses or echo things into
/proc/scsi/scsi. When devices are unplugged, they are
automagically removed from the scsi subsystem, instead of hanging
around registered but with no media actually present.

-Erik

--
Erik B. Andersen http://codepoet-consulting.com/
--This message was written using 73% post-consumer electrons--

Signed-off-by: Erik Andersen <andersen@codepoet.org>

--- orig/drivers/usb/storage/usb.c Fri Sep 17 15:34:38 2004
+++ linux-2.4.27/drivers/usb/storage/usb.c Fri Sep 17 15:34:38 2004
@@ -744,6 +744,11 @@
/* unlock the device pointers */
up(&(ss->dev_semaphore));

+ /* Try to re-connect ourselves to the SCSI subsystem */
+ if (scsi_add_single_device(ss->host, 0, 0, 0))
+ printk(KERN_WARNING "Unable to connect USB device to the SCSI subsystem\n");
+ else
+ printk(KERN_WARNING "USB device connected to the SCSI subsystem\n");
} else {
/* New device -- allocate memory and initialize */
US_DEBUGP("New GUID " GUID_FORMAT "\n", GUID_ARGS(guid));
@@ -1057,6 +1062,12 @@
/* lock access to the device data structure */
down(&(ss->dev_semaphore));

+ /* Try to un-hook ourselves from the SCSI subsystem */
+ if (scsi_remove_single_device(ss->host, 0, 0, 0))
+ printk(KERN_WARNING "Unable to disconnect USB device from the SCSI subsystem\n");
+ else
+ printk(KERN_WARNING "USB device disconnected from the SCSI subsystem\n");
+
/* release the IRQ, if we have one */
if (ss->irq_urb) {
US_DEBUGP("-- releasing irq URB\n");
--- orig/drivers/ieee1394/sbp2.c Fri Sep 17 15:34:38 2004
+++ linux-2.4.27/drivers/ieee1394/sbp2.c Fri Sep 17 15:34:38 2004
@@ -231,7 +231,7 @@
* enable this define to make use of it. This provides better hotplug
* support. The mentioned patch is not part of the kernel proper though,
* because it is considered somewhat of a hack. */
-//#define SBP2_USE_SCSI_ADDREM_HACK
+#define SBP2_USE_SCSI_ADDREM_HACK

/*
--- orig/drivers/scsi/scsi_syms.c Fri Sep 17 15:34:38 2004
+++ linux-2.4.27/drivers/scsi/scsi_syms.c Fri Sep 17 15:34:38 2004
@@ -104,3 +104,9 @@
extern int scsi_delete_timer(Scsi_Cmnd *);
EXPORT_SYMBOL(scsi_add_timer);
EXPORT_SYMBOL(scsi_delete_timer);
+
+/* Support for hot plugging and unplugging devices -- safe for
+ * ieee1394 or USB devices, but probably not for normal SCSI... */
+EXPORT_SYMBOL(scsi_add_single_device);
+EXPORT_SYMBOL(scsi_remove_single_device);
+
--- orig/drivers/scsi/hosts.h Fri Sep 17 15:34:38 2004
+++ linux-2.4.27/drivers/scsi/hosts.h Fri Sep 17 15:34:38 2004
@@ -535,6 +535,13 @@
int scsi_register_device(struct Scsi_Device_Template * sdpnt);
void scsi_deregister_device(struct Scsi_Device_Template * tpnt);

+/* Support for hot plugging and unplugging devices -- safe for
+ * ieee1394 or USB devices, but probably not for normal SCSI... */
+extern int scsi_add_single_device(struct Scsi_Host *shpnt,
+ int channel, int id, int lun);
+extern int scsi_remove_single_device(struct Scsi_Host *shpnt,
+ int channel, int id, int lun);
+
/* These are used by loadable modules */
extern int scsi_register_module(int, void *);
extern int scsi_unregister_module(int, void *);
--- orig/drivers/scsi/scsi.c Fri Sep 17 15:34:38 2004
+++ linux-2.4.27/drivers/scsi/scsi.c Fri Sep 17 15:34:38 2004
@@ -1554,6 +1554,156 @@
}
}

+
+static DECLARE_MUTEX(scsi_host_internals_lock);
+/*
+ * Function: scsi_add_single_device()
+ *
+ * Purpose: Support for hotplugging SCSI devices. This function
+ * implements the actual functionality for
+ * echo "scsi add-single-device 0 1 2 3" >/proc/scsi/scsi
+ *
+ * Arguments: shpnt - pointer to the SCSI host structure
+ * channel - channel of the device to add
+ * id - id of the device to add
+ * lun - lun of the device to add
+ *
+ * Returns: 0 on success or an error code
+ *
+ * Lock status: None needed.
+ *
+ * Notes: This feature is probably unsafe for standard SCSI devices,
+ * but is perfectly normal for things like ieee1394 or USB
+ * drives since these busses are designed for hotplugging.
+ * Use at your own risk....
+ */
+int scsi_add_single_device(struct Scsi_Host *shpnt, int channel,
+ int id, int lun)
+{
+ Scsi_Device *scd;
+
+ /* Do a bit of sanity checking */
+ if (shpnt==NULL) {
+ return -ENXIO;
+ }
+
+ /* We call functions that can sleep, so use a semaphore to
+ * avoid racing with scsi_remove_single_device(). We probably
+ * need to also apply this lock to scsi_register*(),
+ * scsi_unregister*(), sd_open(), sd_release() and anything
+ * else that might be messing with with the Scsi_Host or other
+ * fundamental data structures. */
+ down(&scsi_host_internals_lock);
+
+ /* Check if they asked us to add an already existing device.
+ * If so, ignore their misguided efforts. */
+ for (scd = shpnt->host_queue; scd; scd = scd->next) {
+ if ((scd->channel == channel && scd->id == id && scd->lun == lun)) {
+ break;
+ }
+ }
+ if (scd) {
+ up(&scsi_host_internals_lock);
+ return -ENOSYS;
+ }
+
+ scan_scsis(shpnt, 1, channel, id, lun);
+ up(&scsi_host_internals_lock);
+ return 0;
+}
+
+/*
+ * Function: scsi_remove_single_device()
+ *
+ * Purpose: Support for hot-unplugging SCSI devices. This function
+ * implements the actual functionality for
+ * echo "scsi remove-single-device 0 1 2 3" >/proc/scsi/scsi
+ *
+ * Arguments: shpnt - pointer to the SCSI host structure
+ * channel - channel of the device to add
+ * id - id of the device to add
+ * lun - lun of the device to add
+ *
+ * Returns: 0 on success or an error code
+ *
+ * Lock status: None needed.
+ *
+ * Notes: This feature is probably unsafe for standard SCSI devices,
+ * but is perfectly normal for things like ieee1394 or USB
+ * drives since these busses are designed for hotplugging.
+ * Use at your own risk....
+ */
+int scsi_remove_single_device(struct Scsi_Host *shpnt, int channel,
+ int id, int lun)
+{
+ Scsi_Device *scd;
+ struct Scsi_Device_Template *SDTpnt;
+
+ /* Do a bit of sanity checking */
+ if (shpnt==NULL) {
+ return -ENODEV;
+ }
+
+ /* We call functions that can sleep, so use a semaphore to
+ * avoid racing with scsi_add_single_device(). We probably
+ * need to also apply this lock to scsi_register*(),
+ * scsi_unregister*(), sd_open(), sd_release() and anything
+ * else that might be messing with with the Scsi_Host or other
+ * fundamental data structures. */
+ down(&scsi_host_internals_lock);
+
+ /* Make sure the specified device is in fact present */
+ for (scd = shpnt->host_queue; scd; scd = scd->next) {
+ if ((scd->channel == channel && scd->id == id && scd->lun == lun)) {
+ break;
+ }
+ }
+ if (scd==NULL) {
+ up(&scsi_host_internals_lock);
+ return -ENODEV;
+ }
+
+ /* See if the specified device is busy. Doesn't this race with
+ * sd_open(), sd_release() and similar? Why don't they lock
+ * things when they increment/decrement the access_count? */
+ if (scd->access_count) {
+ up(&scsi_host_internals_lock);
+ return -EBUSY;
+ }
+
+ SDTpnt = scsi_devicelist;
+ while (SDTpnt != NULL) {
+ if (SDTpnt->detach)
+ (*SDTpnt->detach) (scd);
+ SDTpnt = SDTpnt->next;
+ }
+
+ if (scd->attached == 0) {
+ /* Nobody is using this device, so we
+ * can now free all command structures. */
+ if (shpnt->hostt->revoke)
+ shpnt->hostt->revoke(scd);
+ devfs_unregister (scd->de);
+ scsi_release_commandblocks(scd);
+
+ /* Now we can remove the device structure */
+ if (scd->next != NULL)
+ scd->next->prev = scd->prev;
+
+ if (scd->prev != NULL)
+ scd->prev->next = scd->next;
+
+ if (shpnt->host_queue == scd) {
+ shpnt->host_queue = scd->next;
+ }
+ blk_cleanup_queue(&scd->request_queue);
+ kfree((char *) scd);
+ }
+
+ up(&scsi_host_internals_lock);
+ return 0;
+}
+
#ifdef CONFIG_PROC_FS
static int scsi_proc_info(char *buffer, char **start, off_t offset, int length)
{
@@ -1606,8 +1756,6 @@
static int proc_scsi_gen_write(struct file * file, const char * buf,
unsigned long length, void *data)
{
- struct Scsi_Device_Template *SDTpnt;
- Scsi_Device *scd;
struct Scsi_Host *HBA_ptr;
char *p;
int host, channel, id, lun;
@@ -1722,13 +1870,12 @@
/*
* Usage: echo "scsi add-single-device 0 1 2 3" >/proc/scsi/scsi
* with "0 1 2 3" replaced by your "Host Channel Id Lun".
- * Consider this feature BETA.
+ *
+ * Consider this feature pre-BETA.
+ *
* CAUTION: This is not for hotplugging your peripherals. As
* SCSI was not designed for this you could damage your
- * hardware !
- * However perhaps it is legal to switch on an
- * already connected device. It is perhaps not
- * guaranteed this device doesn't corrupt an ongoing data transfer.
+ * hardware and thoroughly confuse the SCSI subsystem.
*/
if (!strncmp("add-single-device", buffer + 5, 17)) {
p = buffer + 23;
@@ -1746,33 +1893,11 @@
break;
}
}
- err = -ENXIO;
- if (!HBA_ptr)
- goto out;
-
- for (scd = HBA_ptr->host_queue; scd; scd = scd->next) {
- if ((scd->channel == channel
- && scd->id == id
- && scd->lun == lun)) {
- break;
- }
- }
-
- err = -ENOSYS;
- if (scd)
- goto out; /* We do not yet support unplugging */
-
- scan_scsis(HBA_ptr, 1, channel, id, lun);
-
- /* FIXME (DB) This assumes that the queue_depth routines can be used
- in this context as well, while they were all designed to be
- called only once after the detect routine. (DB) */
- /* queue_depth routine moved to inside scan_scsis(,1,,,) so
- it is called before build_commandblocks() */
-
- err = length;
+ if ((err=scsi_add_single_device(HBA_ptr, channel, id, lun))==0)
+ err = length;
goto out;
}
+
/*
* Usage: echo "scsi remove-single-device 0 1 2 3" >/proc/scsi/scsi
* with "0 1 2 3" replaced by your "Host Channel Id Lun".
@@ -1782,7 +1907,6 @@
* CAUTION: This is not for hotplugging your peripherals. As
* SCSI was not designed for this you could damage your
* hardware and thoroughly confuse the SCSI subsystem.
- *
*/
else if (!strncmp("remove-single-device", buffer + 5, 20)) {
p = buffer + 26;
@@ -1798,58 +1922,8 @@
break;
}
}
- err = -ENODEV;
- if (!HBA_ptr)
- goto out;
-
- for (scd = HBA_ptr->host_queue; scd; scd = scd->next) {
- if ((scd->channel == channel
- && scd->id == id
- && scd->lun == lun)) {
- break;
- }
- }
-
- if (scd == NULL)
- goto out; /* there is no such device attached */
-
- err = -EBUSY;
- if (scd->access_count)
- goto out;
-
- SDTpnt = scsi_devicelist;
- while (SDTpnt != NULL) {
- if (SDTpnt->detach)
- (*SDTpnt->detach) (scd);
- SDTpnt = SDTpnt->next;
- }
-
- if (scd->attached == 0) {
- /*
- * Nobody is using this device any more.
- * Free all of the command structures.
- */
- if (HBA_ptr->hostt->revoke)
- HBA_ptr->hostt->revoke(scd);
- devfs_unregister (scd->de);
- scsi_release_commandblocks(scd);
-
- /* Now we can remove the device structure */
- if (scd->next != NULL)
- scd->next->prev = scd->prev;
-
- if (scd->prev != NULL)
- scd->prev->next = scd->next;
-
- if (HBA_ptr->host_queue == scd) {
- HBA_ptr->host_queue = scd->next;
- }
- blk_cleanup_queue(&scd->request_queue);
- kfree((char *) scd);
- } else {
- goto out;
- }
- err = 0;
+ err=scsi_remove_single_device(HBA_ptr, channel, id, lun);
+ goto out;
}
out:

-
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>
> Raúl Núñez de Arenas Coronado
>
> --
> Linux Registered User 88736 | http://www.dervishd.net
> http://www.pleyades.net & http://www.gotesdelluna.net
> It's my PC and I'll cry if I want to...
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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