[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/sd.h b/drivers/scsi/sd.h
index 47c52a6..74a1e4c 100644
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -14,6 +14,7 @@
#define SD_TIMEOUT (30 * HZ)
#define SD_MOD_TIMEOUT (75 * HZ)
#define SD_FLUSH_TIMEOUT (60 * HZ)
+#define SD_WRITE_SAME_TIMEOUT (120 * HZ)
/*
* Number of allowed retries
@@ -39,6 +40,11 @@
};
enum {
+ SD_MAX_WS10_BLOCKS = 0xffff,
+ SD_MAX_WS16_BLOCKS = 0x7fffff,
+};
+
+enum {
SD_LBP_FULL = 0, /* Full logical block provisioning */
SD_LBP_UNMAP, /* Use UNMAP command */
SD_LBP_WS16, /* Use WRITE SAME(16) with UNMAP bit */
@@ -77,6 +83,7 @@
unsigned lbpws : 1;
unsigned lbpws10 : 1;
unsigned lbpvpd : 1;
+ unsigned ws16 : 1;
};
#define to_scsi_disk(obj) container_of(obj,struct scsi_disk,dev)