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[SCSI] sd: Refactor sd_read_capacity()
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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>
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Matthew Wilcox authored and James Bottomley committed Mar 14, 2009
1 parent 635374e commit 0da205e
Showing 1 changed file with 155 additions and 86 deletions.
241 changes: 155 additions & 86 deletions drivers/scsi/sd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1273,115 +1273,184 @@ void sd_read_protection_type(struct scsi_disk *sdkp, unsigned char *buffer)
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);
retries--;

} 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
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