[SCSI] sd: Refactor sd_read_capacity()
authorMatthew Wilcox <matthew@wil.cx>
Thu, 12 Mar 2009 18:20:29 +0000 (14:20 -0400)
committerJames Bottomley <James.Bottomley@HansenPartnership.com>
Sat, 14 Mar 2009 13:42:56 +0000 (08:42 -0500)
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.

[jejb: upped transfer request to standard recommended 32 for RC16]
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
drivers/scsi/sd.c

index e744ee4..dcff84a 100644 (file)
@@ -1273,42 +1273,61 @@ 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 32
+#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);
@@ -1316,72 +1335,122 @@ 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 are known to return the total number of blocks,
         * not the highest block number.  Some devices have versions