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[SCSI] sd: Implement support for WRITE SAME

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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>
This commit is contained in:
Martin K. Petersen
2012-09-18 12:19:32 -04:00
committed by James Bottomley
parent 26e85fcd15
commit 5db44863b6
7 changed files with 191 additions and 16 deletions
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7
drivers/scsi/sd.h
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@@ -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
@@ -38,6 +39,11 @@ enum {
SD_MEMPOOL_SIZE = 2, /* CDB pool size */
};
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 */
@@ -77,6 +83,7 @@ struct scsi_disk {
unsigned lbpws : 1;
unsigned lbpws10 : 1;
unsigned lbpvpd : 1;
unsigned ws16 : 1;
};
#define to_scsi_disk(obj) container_of(obj,struct scsi_disk,dev)