sd: Try READ CAPACITY 16 first for all SCSI-3 devices

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"Matthew" == Matthew Wilcox <[email protected]> writes:

I've been running with this on my DIF drives for a few days and everything looked fine.

The bad news is that I have one particular drive model that after a failed READ CAPACITY(16) command responds correctly to READ CAPACITY(10). And *then* the drive firmware commits suicide.

At least for DIF I have an innocuous INQUIRY field to key off of. Long term I think we should check the Block Limits thin provisioning bits.

2005), so I'm OK with this change. I'll send updated patches (the first patch now needs an extra NULL argument to scsi_execute_request).

Quoted 2 lines · Matthew Wilcox

2005), so I'm OK with this change. I'll send updated patches (the first patch now needs an extra NULL argument to scsi_execute_request).

commit 039f215a451eaa0cb04ae75e7506f178759e24e3

Author: Matthew Wilcox <[email protected]>
Date:   Wed Dec 31 07:30:12 2008 -0500

sd: Refactor sd_read_capacity()

The sd_read_capacity() function was about 180 lines long and included a backwards goto and a tricky state variable. Splitting out read_capacity_10() and read_capacity_16() (about 50 lines each) reduces sd_read_capacity to about 100 lines and gets rid of the backwards goto and the state variable. I've tried to avoid any behaviour change with this patch.

Signed-off-by Matthew Wilcox <[email protected]>

drivers/scsi/sd.c +155 -86

index 62b28d5..06bb638 100644
@@ -1275,42 +1275,61 @@ disable:
 	sdkp->capacity = 0;
 }
 
-/*
- * read disk capacity
- */
-static void
-sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
+static void read_capacity_error(struct scsi_disk *sdkp, struct scsi_device *sdp,
+			struct scsi_sense_hdr *sshdr, int sense_valid,
+			int the_result)
+{
+	sd_print_result(sdkp, the_result);
+	if (driver_byte(the_result) & DRIVER_SENSE)
+		sd_print_sense_hdr(sdkp, sshdr);
+	else
+		sd_printk(KERN_NOTICE, sdkp, "Sense not available.\n");
+
+	/*
+	 * Set dirty bit for removable devices if not ready -
+	 * sometimes drives will not report this properly.
+	 */
+	if (sdp->removable &&
+	    sense_valid && sshdr->sense_key == NOT_READY)
+		sdp->changed = 1;
+
+	/*
+	 * We used to set media_present to 0 here to indicate no media
+	 * in the drive, but some drives fail read capacity even with
+	 * media present, so we can't do that.
+	 */
+	sdkp->capacity = 0; /* unknown mapped to zero - as usual */
+}
+
+#define RC16_LEN 13
+#if RC16_LEN > SD_BUF_SIZE
+#error RC16_LEN must not be more than SD_BUF_SIZE
+#endif
+
+static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
+						unsigned char *buffer)
 {
 	unsigned char cmd[16];
-	int the_result, retries;
-	int sector_size = 0;
-	/* Force READ CAPACITY(16) when PROTECT=1 */
-	int longrc = scsi_device_protection(sdkp->device) ? 1 : 0;
 	struct scsi_sense_hdr sshdr;
 	int sense_valid = 0;
-	struct scsi_device *sdp = sdkp->device;
+	int the_result;
+	int retries = 3;
+	unsigned long long lba;
+	unsigned sector_size;
 
-repeat:
-	retries = 3;
 	do {
-		if (longrc) {
-			memset((void *) cmd, 0, 16);
-			cmd[0] = SERVICE_ACTION_IN;
-			cmd[1] = SAI_READ_CAPACITY_16;
-			cmd[13] = 13;
-			memset((void *) buffer, 0, 13);
-		} else {
-			cmd[0] = READ_CAPACITY;
-			memset((void *) &cmd[1], 0, 9);
-			memset((void *) buffer, 0, 8);
-		}
-		
+		memset(cmd, 0, 16);
+		cmd[0] = SERVICE_ACTION_IN;
+		cmd[1] = SAI_READ_CAPACITY_16;
+		cmd[13] = RC16_LEN;
+		memset(buffer, 0, RC16_LEN);
+
 		the_result = scsi_execute_req(sdp, cmd, DMA_FROM_DEVICE,
-					      buffer, longrc ? 13 : 8, &sshdr,
-					      SD_TIMEOUT, SD_MAX_RETRIES, NULL);
+					buffer, RC16_LEN, &sshdr,
+					SD_TIMEOUT, SD_MAX_RETRIES, NULL);
 
 		if (media_not_present(sdkp, &sshdr))
-			return;
+			return -ENODEV;
 
 		if (the_result)
 			sense_valid = scsi_sense_valid(&sshdr);

@@ -1318,72 +1337,122 @@ repeat:
 
 	} while (the_result && retries);
 
-	if (the_result && !longrc) {
+	if (the_result) {
+		sd_printk(KERN_NOTICE, sdkp, "READ CAPACITY(16) failed\n");
+		read_capacity_error(sdkp, sdp, &sshdr, sense_valid, the_result);
+		return -EINVAL;
+	}
+
+	sector_size =	(buffer[8] << 24) | (buffer[9] << 16) |
+			(buffer[10] << 8) | buffer[11];
+	lba =  (((u64)buffer[0] << 56) | ((u64)buffer[1] << 48) |
+		((u64)buffer[2] << 40) | ((u64)buffer[3] << 32) |
+		((u64)buffer[4] << 24) | ((u64)buffer[5] << 16) |
+		((u64)buffer[6] << 8) | (u64)buffer[7]);
+
+	sd_read_protection_type(sdkp, buffer);
+
+	if ((sizeof(sdkp->capacity) == 4) && (lba >= 0xffffffffULL)) {
+		sd_printk(KERN_ERR, sdkp, "Too big for this kernel. Use a "
+			"kernel compiled with support for large block "
+			"devices.\n");
+		sdkp->capacity = 0;
+		return -EOVERFLOW;
+	}
+
+	sdkp->capacity = lba + 1;
+	return sector_size;
+}
+
+static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
+						unsigned char *buffer)
+{
+	unsigned char cmd[16];
+	struct scsi_sense_hdr sshdr;
+	int sense_valid = 0;
+	int the_result;
+	int retries = 3;
+	sector_t lba;
+	unsigned sector_size;
+
+	do {
+		cmd[0] = READ_CAPACITY;
+		memset(&cmd[1], 0, 9);
+		memset(buffer, 0, 8);
+
+		the_result = scsi_execute_req(sdp, cmd, DMA_FROM_DEVICE,
+					buffer, 8, &sshdr,
+					SD_TIMEOUT, SD_MAX_RETRIES, NULL);
+
+		if (media_not_present(sdkp, &sshdr))
+			return -ENODEV;
+
+		if (the_result)
+			sense_valid = scsi_sense_valid(&sshdr);
+		retries--;
+
+	} while (the_result && retries);
+
+	if (the_result) {
 		sd_printk(KERN_NOTICE, sdkp, "READ CAPACITY failed\n");
-		sd_print_result(sdkp, the_result);
-		if (driver_byte(the_result) & DRIVER_SENSE)
-			sd_print_sense_hdr(sdkp, &sshdr);
-		else
-			sd_printk(KERN_NOTICE, sdkp, "Sense not available.\n");
+		read_capacity_error(sdkp, sdp, &sshdr, sense_valid, the_result);
+		return -EINVAL;
+	}
 
-		/* Set dirty bit for removable devices if not ready -
-		 * sometimes drives will not report this properly. */
-		if (sdp->removable &&
-		    sense_valid && sshdr.sense_key == NOT_READY)
-			sdp->changed = 1;
+	sector_size =	(buffer[4] << 24) | (buffer[5] << 16) |
+			(buffer[6] << 8) | buffer[7];
+	lba =	(buffer[0] << 24) | (buffer[1] << 16) |
+		(buffer[2] << 8) | buffer[3];
 
-		/* Either no media are present but the drive didn't tell us,
-		   or they are present but the read capacity command fails */
-		/* sdkp->media_present = 0; -- not always correct */
-		sdkp->capacity = 0; /* unknown mapped to zero - as usual */
+	if ((sizeof(sdkp->capacity) == 4) && (lba == 0xffffffff)) {
+		sd_printk(KERN_ERR, sdkp, "Too big for this kernel. Use a "
+			"kernel compiled with support for large block "
+			"devices.\n");
+		sdkp->capacity = 0;
+		return -EOVERFLOW;
+	}
 
-		return;
-	} else if (the_result && longrc) {
-		/* READ CAPACITY(16) has been failed */
-		sd_printk(KERN_NOTICE, sdkp, "READ CAPACITY(16) failed\n");
-		sd_print_result(sdkp, the_result);
-		sd_printk(KERN_NOTICE, sdkp, "Use 0xffffffff as device size\n");
+	sdkp->capacity = lba + 1;
+	return sector_size;
+}
 
-		sdkp->capacity = 1 + (sector_t) 0xffffffff;		
-		goto got_data;
-	}	
-	
-	if (!longrc) {
-		sector_size = (buffer[4] << 24) |
-			(buffer[5] << 16) | (buffer[6] << 8) | buffer[7];
-		if (buffer[0] == 0xff && buffer[1] == 0xff &&
-		    buffer[2] == 0xff && buffer[3] == 0xff) {
-			if(sizeof(sdkp->capacity) > 4) {
-				sd_printk(KERN_NOTICE, sdkp, "Very big device. "
-					  "Trying to use READ CAPACITY(16).\n");
-				longrc = 1;
-				goto repeat;
-			}
-			sd_printk(KERN_ERR, sdkp, "Too big for this kernel. Use "
-				  "a kernel compiled with support for large "
-				  "block devices.\n");
-			sdkp->capacity = 0;
+/*
+ * read disk capacity
+ */
+static void
+sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
+{
+	int sector_size;
+	struct scsi_device *sdp = sdkp->device;
+
+	/* Force READ CAPACITY(16) when PROTECT=1 */
+	if (scsi_device_protection(sdp)) {
+		sector_size = read_capacity_16(sdkp, sdp, buffer);
+		if (sector_size == -EOVERFLOW)
 			goto got_data;
-		}
-		sdkp->capacity = 1 + (((sector_t)buffer[0] << 24) |
-			(buffer[1] << 16) |
-			(buffer[2] << 8) |
-			buffer[3]);			
+		if (sector_size < 0)
+			return;
 	} else {
-		sdkp->capacity = 1 + (((u64)buffer[0] << 56) |
-			((u64)buffer[1] << 48) |
-			((u64)buffer[2] << 40) |
-			((u64)buffer[3] << 32) |
-			((sector_t)buffer[4] << 24) |
-			((sector_t)buffer[5] << 16) |
-			((sector_t)buffer[6] << 8)  |
-			(sector_t)buffer[7]);
-			
-		sector_size = (buffer[8] << 24) |
-			(buffer[9] << 16) | (buffer[10] << 8) | buffer[11];
-
-		sd_read_protection_type(sdkp, buffer);
-	}	
+		sector_size = read_capacity_10(sdkp, sdp, buffer);
+		if (sector_size == -EOVERFLOW)
+			goto got_data;
+		if (sector_size < 0)
+			return;
+		if ((sizeof(sdkp->capacity) > 4) &&
+		    (sdkp->capacity > 0xffffffffULL)) {
+			int old_sector_size = sector_size;
+			sd_printk(KERN_NOTICE, sdkp, "Very big device. "
+					"Trying to use READ CAPACITY(16).\n");
+			sector_size = read_capacity_16(sdkp, sdp, buffer);
+			if (sector_size < 0) {
+				sd_printk(KERN_NOTICE, sdkp,
+					"Using 0xffffffff as device size\n");
+				sdkp->capacity = 1 + (sector_t) 0xffffffff;
+				sector_size = old_sector_size;
+				goto got_data;
+			}
+		}
+	}
 
 	/* Some devices return the total number of sectors, not the
 	 * highest sector number.  Make the necessary adjustment. */

Signature · 5 lines

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."

Any reason this patch hasn't been merged into scsi-misc yet?

Quoted 1 line · Matthew Wilcox

Any reason this patch hasn't been merged into scsi-misc yet?

There was a problem with it I drew your attention to here:

http://marc.info/?l=linux-scsi&m=123308499405071

Quoted 6 lines · James Bottomley

Quoted 1 line · Matthew Wilcox

Any reason this patch hasn't been merged into scsi-misc yet?

There was a problem with it I drew your attention to here:

http://marc.info/?l=linux-scsi&m=123308499405071

This was the updated version, sent on Dec 31, not the version you commented on on Dec 23.

New features are being added to the READ CAPACITY 16 results, so we want to try to issue it in preference to READ CAPACITY 10. Unfortunately, some USB devices hang when they see a READ CAPACITY 16, so we limit our chances of causing a hang by restricting this command to devices which claim conformance to SCSI-3. USB devices are currently limited to claiming at most SCSI-2 conformance.

Of course, it's entirely legitimate for devices to not implement READ CAPACITY 16, so this patch also includes a fallback to READ CAPACITY 10 for SCSI-3 devices.

Signed-off-by Matthew Wilcox <[email protected]>

---
 drivers/scsi/sd.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

drivers/scsi/sd.c +0 -0

index f244349..25a923b 100644