James, Boaz, or anyone else:
Can you comment on this patch? Is the test inserted at the right
place? Have I left anything out or forgotten anything? (This is just
the SCSI part of the patch; the usb-storage part is separate.)
Thanks,
Alan Stern
Add a new scsi_device flag to tell sd.c that it should verify the
results of READ CAPACITY by trying the read the last sector. This is
necessary because a large percentage of USB mass-storage devices -- too
many for a blacklist -- have a bug whereby they return the total number
of sectors rather than the index of the last sector.
The new sd_read_last_sector() routine carries out the test, using a
very short timeout and a small number of retries. Any working device
for which the check_capacity flag is set should be able to pass the
test easily.
Index: usb-2.6/include/scsi/scsi_device.h
===================================================================
--- usb-2.6.orig/include/scsi/scsi_device.h
+++ usb-2.6/include/scsi/scsi_device.h
@@ -142,6 +142,7 @@ struct scsi_device {
unsigned select_no_atn:1;
unsigned fix_capacity:1; /* READ_CAPACITY is too high by 1 */
unsigned guess_capacity:1; /* READ_CAPACITY might be too high by 1 */
+ unsigned check_capacity:1; /* Verify READ_CAPACITY result */
unsigned retry_hwerror:1; /* Retry HARDWARE_ERROR */
unsigned last_sector_bug:1; /* do not use multisector accesses on
SD_LAST_BUGGY_SECTORS */
Index: usb-2.6/drivers/scsi/sd.c
===================================================================
--- usb-2.6.orig/drivers/scsi/sd.c
+++ usb-2.6/drivers/scsi/sd.c
@@ -1275,6 +1275,88 @@ disable:
sdkp->capacity = 0;
}
+#if defined(CONFIG_USB_STORAGE) || defined(CONFIG_USB_STORAGE_MODULE)
+/*
+ * Test disk capacity by trying to read the last sector
+ */
+static int sd_read_last_sector(struct scsi_disk *sdkp, unsigned char *buffer,
+ int sector_size)
+{
+ struct scsi_device *sdp = sdkp->device;
+ u32 last;
+ int result, resid;
+ int rc = 0;
+ unsigned char cmd[10];
+
+ /* If the capacity is unknown, assume we're okay */
+ if (sdkp->capacity <= 0)
+ return rc;
+
+ sdp->check_capacity = 0; /* One test should be enough */
+
+ /* If the device doesn't use READ(10), assume we're okay */
+ if (!sdp->use_10_for_rw)
+ return rc;
+
+ /* If the capacity is too big for READ(10), assume we're okay */
+ if (sdkp->capacity > 0xffffffff)
+ return rc;
+
+ /* If the sector size is too big, assume we're okay */
+ if (sector_size > SD_BUF_SIZE)
+ return rc;
+ if (sector_size == 0)
+ sector_size = 512;
+
+ if (!sdkp->openers++ && sdp->removable)
+ scsi_set_medium_removal(sdp, SCSI_REMOVAL_PREVENT);
+
+ /* Start by trying to read the first sector, just to warm up */
+ memset(cmd, 0, 10);
+ cmd[0] = READ_10;
+ cmd[8] = 1;
+ result = scsi_execute_req(sdp, cmd, DMA_FROM_DEVICE,
+ buffer, sector_size, NULL,
+ SD_TIMEOUT, SD_MAX_RETRIES, &resid);
+ if (result || resid) {
+ sdp->check_capacity = 1; /* Try again later */
+ goto done;
+ }
+
+ /* Now try to read the last sector */
+ last = sdkp->capacity - 1;
+ cmd[2] = (last >> 24);
+ cmd[3] = (last >> 16);
+ cmd[4] = (last >> 8);
+ cmd[5] = last;
+
+ /* Allow only 1 retry, with a short timeout (some devices
+ * violate protocol, forcing the command to be aborted).
+ */
+ result = scsi_execute_req(sdp, cmd, DMA_FROM_DEVICE,
+ buffer, sector_size, NULL, HZ, 1, &resid);
+ if (result || resid) {
+ sdp->fix_capacity = 1; /* For next time */
+ rc = -EIO;
+ }
+
+ done:
+ if (!--sdkp->openers && sdp->removable) {
+ if (scsi_block_when_processing_errors(sdp))
+ scsi_set_medium_removal(sdp, SCSI_REMOVAL_ALLOW);
+ }
+ return rc;
+}
+
+#else
+static inline int sd_read_last_sector(struct scsi_disk *sdkp,
+ unsigned char *buffer, int sector_size)
+{
+ return 0;
+}
+
+#endif /* defined(CONFIG_USB_STORAGE) || ... */
+
/*
* read disk capacity
*/
@@ -1396,7 +1478,9 @@ repeat:
* the capacity.
*/
if (sdp->fix_capacity ||
- (sdp->guess_capacity && (sdkp->capacity & 0x01))) {
+ (sdp->guess_capacity && (sdkp->capacity & 0x01)) ||
+ (sdp->check_capacity &&
+ sd_read_last_sector(sdkp, buffer, sector_size) < 0)) {
sd_printk(KERN_INFO, sdkp, "Adjusting the sector count "
"from its reported value: %llu\n",
(unsigned long long) sdkp->capacity);
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
