From: Kay Sievers <kay.sievers@xxxxxxxx>
Some broken devices indicates that media has changed on every
GET_EVENT_STATUS_NOTIFICATION. This translates into MEDIA_CHANGE
uevent on every open() which lets udev run into a loop.
Verify GET_EVENT result against TUR and if it generates spurious
events for several times in a row, ignore the GET_EVENT events, and
trust only the TUR status.
This is the log of a USB stick with a (broken) fake CDROM drive:
scsi 5:0:0:0: Direct-Access SanDisk U3 Cruzer Micro 8.02 PQ: 0 ANSI: 0 CCS
sd 5:0:0:0: Attached scsi generic sg3 type 0
scsi 5:0:0:1: CD-ROM SanDisk U3 Cruzer Micro 8.02 PQ: 0 ANSI: 0
sd 5:0:0:0: [sdb] Attached SCSI removable disk
sr2: scsi3-mmc drive: 48x/48x tray
sr 5:0:0:1: Attached scsi CD-ROM sr2
sr 5:0:0:1: Attached scsi generic sg4 type 5
sr2: GET_EVENT and TUR disagree continuously, suppress GET_EVENT events
sd 5:0:0:0: [sdb] 31777279 512-byte logical blocks: (16.2 GB/15.1 GiB)
sd 5:0:0:0: [sdb] No Caching mode page present
sd 5:0:0:0: [sdb] Assuming drive cache: write through
sd 5:0:0:0: [sdb] No Caching mode page present
sd 5:0:0:0: [sdb] Assuming drive cache: write through
sdb: sdb1
-tj: Updated to consider only spurious GET_EVENT events among
different types of disagreement and allow using TUR for kernel
event polling after GET_EVENT is ignored.
Reported-By: Markus Rathgeb maggu2810@xxxxxxxxxxxxxx
Signed-off-by: Kay Sievers <kay.sievers@xxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: stable@xxxxxxxxxx # >= v2.6.38, fixes udev busy looping w/ certain devices
---
drivers/scsi/sr.c | 46 ++++++++++++++++++++++++++++++++++++++++++----
drivers/scsi/sr.h | 7 +++++++
2 files changed, 49 insertions(+), 4 deletions(-)
diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index 4778e27..5fc97d2 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -221,14 +221,33 @@ static unsigned int sr_check_events(struct cdrom_device_info *cdi,
return 0;
events = sr_get_events(cd->device);
+ cd->get_event_changed |= events & DISK_EVENT_MEDIA_CHANGE;
+
+ /*
+ * If earlier GET_EVENT_STATUS_NOTIFICATION and TUR did not agree
+ * for several times in a row. We rely on TUR only for this likely
+ * broken device, to prevent generating incorrect media changed
+ * events for every open().
+ */
+ if (cd->ignore_get_event) {
+ events &= ~DISK_EVENT_MEDIA_CHANGE;
+ goto do_tur;
+ }
+
/*
* GET_EVENT_STATUS_NOTIFICATION is enough unless MEDIA_CHANGE
* is being cleared. Note that there are devices which hang
* if asked to execute TUR repeatedly.
*/
- if (!(clearing & DISK_EVENT_MEDIA_CHANGE))
- goto skip_tur;
+ if (cd->device->changed) {
+ events |= DISK_EVENT_MEDIA_CHANGE;
+ cd->device->changed = 0;
+ cd->tur_changed = true;
+ }
+ if (!(clearing & DISK_EVENT_MEDIA_CHANGE))
+ return events;
+do_tur:
/* let's see whether the media is there with TUR */
last_present = cd->media_present;
ret = scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES, &sshdr);
@@ -242,12 +261,31 @@ static unsigned int sr_check_events(struct cdrom_device_info *cdi,
(scsi_sense_valid(&sshdr) && sshdr.asc != 0x3a);
if (last_present != cd->media_present)
- events |= DISK_EVENT_MEDIA_CHANGE;
-skip_tur:
+ cd->device->changed = 1;
+
if (cd->device->changed) {
events |= DISK_EVENT_MEDIA_CHANGE;
cd->device->changed = 0;
+ cd->tur_changed = true;
+ }
+
+ if (cd->ignore_get_event)
+ return events;
+
+ /* check whether GET_EVENT is reporting spurious MEDIA_CHANGE */
+ if (!cd->tur_changed) {
+ if (cd->get_event_changed) {
+ if (cd->tur_mismatch++ > 8) {
+ sdev_printk(KERN_WARNING, cd->device,
+ "GET_EVENT and TUR disagree continuously, suppress GET_EVENT events\n");
+ cd->ignore_get_event = true;
+ }
+ } else {
+ cd->tur_mismatch = 0;
+ }
}
+ cd->tur_changed = false;
+ cd->get_event_changed = false;
return events;
}
diff --git a/drivers/scsi/sr.h b/drivers/scsi/sr.h
index e036f1d..37c8f6b 100644
--- a/drivers/scsi/sr.h
+++ b/drivers/scsi/sr.h
@@ -41,6 +41,13 @@ typedef struct scsi_cd {
unsigned readcd_known:1; /* drive supports READ_CD (0xbe) */
unsigned readcd_cdda:1; /* reading audio data using READ_CD */
unsigned media_present:1; /* media is present */
+
+ /* GET_EVENT spurious event handling, blk layer guarantees exclusion */
+ int tur_mismatch; /* nr of get_event TUR mismatches */
+ bool tur_changed:1; /* changed according to TUR */
+ bool get_event_changed:1; /* changed according to GET_EVENT */
+ bool ignore_get_event:1; /* GET_EVENT is unreliable, use TUR */
+
struct cdrom_device_info cdi;
/* We hold gendisk and scsi_device references on probe and use
* the refs on this kref to decide when to release them */
--
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