[SCSI] sd: Implement support for WRITE SAME
Implement support for WRITE SAME(10) and WRITE SAME(16) in the SCSI disk
driver.
- We set the default maximum to 0xFFFF because there are several
devices out there that only support two-byte block counts even with
WRITE SAME(16). We only enable transfers bigger than 0xFFFF if the
device explicitly reports MAXIMUM WRITE SAME LENGTH in the BLOCK
LIMITS VPD.
- max_write_same_blocks can be overriden per-device basis in sysfs.
- The UNMAP discovery heuristics remain unchanged but the discard
limits are tweaked to match the "real" WRITE SAME commands.
- In the error handling logic we now distinguish between WRITE SAME
with and without UNMAP set.
The discovery process heuristics are:
- If the device reports a SCSI level of SPC-3 or greater we'll issue
READ SUPPORTED OPERATION CODES to find out whether WRITE SAME(16) is
supported. If that's the case we will use it.
- If the device supports the block limits VPD and reports a MAXIMUM
WRITE SAME LENGTH bigger than 0xFFFF we will use WRITE SAME(16).
- Otherwise we will use WRITE SAME(10) unless the target LBA is beyond
0xFFFFFFFF or the block count exceeds 0xFFFF.
- no_write_same is set for ATA, FireWire and USB.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index da36a3a..9032e91 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -900,11 +900,23 @@
action = ACTION_FAIL;
error = -EILSEQ;
/* INVALID COMMAND OPCODE or INVALID FIELD IN CDB */
- } else if ((sshdr.asc == 0x20 || sshdr.asc == 0x24) &&
- (cmd->cmnd[0] == UNMAP ||
- cmd->cmnd[0] == WRITE_SAME_16 ||
- cmd->cmnd[0] == WRITE_SAME)) {
- description = "Discard failure";
+ } else if (sshdr.asc == 0x20 || sshdr.asc == 0x24) {
+ switch (cmd->cmnd[0]) {
+ case UNMAP:
+ description = "Discard failure";
+ break;
+ case WRITE_SAME:
+ case WRITE_SAME_16:
+ if (cmd->cmnd[1] & 0x8)
+ description = "Discard failure";
+ else
+ description =
+ "Write same failure";
+ break;
+ default:
+ description = "Invalid command failure";
+ break;
+ }
action = ACTION_FAIL;
error = -EREMOTEIO;
} else