This patch (as1196) adds 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.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
---
James & Greg:
Although part of this patch touches usb-storage, the majority of
it affects SCSI files. Is it okay if the whole thing goes in via
James's tree?
Alan Stern
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
@@ -1426,6 +1426,89 @@ static int sd_try_rc16_first(struct scsi
return 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, we can't test anything */
+ if (sdkp->capacity <= 0)
+ return rc;
+
+ /* One test should be enough (unless it's inconclusive) */
+ sdp->check_capacity = 0;
+
+ /* 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
*/
@@ -1479,7 +1562,9 @@ sd_read_capacity(struct scsi_disk *sdkp,
* 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);
Index: usb-2.6/drivers/usb/storage/scsiglue.c
===================================================================
--- usb-2.6.orig/drivers/usb/storage/scsiglue.c
+++ usb-2.6/drivers/usb/storage/scsiglue.c
@@ -209,6 +209,14 @@ static int slave_configure(struct scsi_d
if (us->fflags & US_FL_CAPACITY_HEURISTICS)
sdev->guess_capacity = 1;
+ /* To catch devices that have the READ CAPACITY bug and
+ * aren't on our blacklist, tell the SCSI disk driver to
+ * test the last sector. This flag will be ignored if
+ * either of the previous flags causes the capacity to
+ * be decremented. */
+ if (!(us->fflags & US_FL_CAPACITY_OK))
+ sdev->check_capacity = 1;
+
/* assume SPC3 or latter devices support sense size > 18 */
if (sdev->scsi_level > SCSI_SPC_2)
us->fflags |= US_FL_SANE_SENSE;
Index: usb-2.6/drivers/usb/storage/transport.c
===================================================================
--- usb-2.6.orig/drivers/usb/storage/transport.c
+++ usb-2.6/drivers/usb/storage/transport.c
@@ -560,6 +560,12 @@ static void last_sector_hacks(struct us_
if (sector + 1 != sdkp->capacity)
goto done;
+ /* Has the capacity already been decremented? */
+ if (sdkp->device->fix_capacity) {
+ us->use_last_sector_hacks = 0;
+ return;
+ }
+
if (srb->result == SAM_STAT_GOOD && scsi_get_resid(srb) == 0) {
/* The command succeeded. We know this device doesn't
--
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