This is a replacement and extension of the patch
titled:
"[PATCH] sg: retrofit SG_FLAG_Q_AT_TAIL flag"
The aim is to give control over midlevel queuing
when commands are submitted via the sg, bsg and
the block layer SG_IO ioctl pass-throughs. The
current defaults remain: sg and bsg queue at_head
while the block layer SG_IO ioctl queues at_tail .
This patch allows user space programs that care to
override the default queuing for the sg driver and
the block layer SG_IO ioctl. The bsg driver already
has this capability.
This patch is against lk 2.6.33
Changelog
- add SG_FLAG_Q_AT_TAIL and add SG_FLAG_Q_AT_HEAD
flags to sg.h
- act on these flags in the sg driver and the
block layer SG_IO ioctl
- correct stale urls in the sg driver code
Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
--- linux/include/scsi/sg.h 2008-10-10 17:04:54.000000000 -0400
+++ linux/include/scsi/sg.h2633qat2 2010-03-23 18:58:28.000000000 -0400
@@ -11,12 +11,12 @@
Original driver (sg.h):
* Copyright (C) 1992 Lawrence Foard
Version 2 and 3 extensions to driver:
-* Copyright (C) 1998 - 2006 Douglas Gilbert
+* Copyright (C) 1998 - 2010 Douglas Gilbert
- Version: 3.5.34 (20060920)
+ Version: 3.5.35 (20100323)
This version is for 2.6 series kernels.
- For a full changelog see http://www.torque.net/sg
+ For a full changelog see http://sg.danny.cz/sg
Map of SG verions to the Linux kernels in which they appear:
---------- ----------------------------------
@@ -52,17 +52,17 @@
Documentation
=============
A web site for the SG device driver can be found at:
- http://www.torque.net/sg [alternatively check the MAINTAINERS file]
+ http://sg.danny.cz/sg [alternatively check the MAINTAINERS file]
The documentation for the sg version 3 driver can be found at:
- http://www.torque.net/sg/p/sg_v3_ho.html
+ http://sg.danny.cz/sg/p/sg_v3_ho.html
This is a rendering from DocBook source [change the extension to "sgml"
or "xml"]. There are renderings in "ps", "pdf", "rtf" and "txt" (soon).
The SG_IO ioctl is now found in other parts kernel (e.g. the block layer).
- For more information see http://www.torque.net/sg/sg_io.html
+ For more information see http://sg.danny.cz/sg/sg_io.html
The older, version 2 documents discuss the original sg interface in detail:
- http://www.torque.net/sg/p/scsi-generic.txt
- http://www.torque.net/sg/p/scsi-generic_long.txt
+ http://sg.danny.cz/sg/p/scsi-generic.txt
+ http://sg.danny.cz/sg/p/scsi-generic_long.txt
Also available: <kernel_source>/Documentation/scsi/scsi-generic.txt
Utility and test programs are available at the sg web site. They are
@@ -124,6 +124,9 @@
#define SG_FLAG_UNUSED_LUN_INHIBIT 2 /* default is overwrite lun in SCSI */
/* command block (when <= SCSI_2) */
#define SG_FLAG_MMAP_IO 4 /* request memory mapped IO */
+/* If initiator cannot take command, midlevel queue discipline override */
+#define SG_FLAG_Q_AT_TAIL 0x10 /* default action of block layer SG_IO */
+#define SG_FLAG_Q_AT_HEAD 0x20 /* default action of sg and bsg drivers */
#define SG_FLAG_NO_DXFER 0x10000 /* no transfer of kernel buffers to/from */
/* user space (debug indirect IO) */
--- linux/drivers/scsi/sg.c 2009-12-03 11:11:18.000000000 -0500
+++ linux/drivers/scsi/sg.c2633qat2 2010-03-23 21:09:05.000000000 -0400
@@ -7,7 +7,7 @@
* Original driver (sg.c):
* Copyright (C) 1992 Lawrence Foard
* Version 2 and 3 extensions to driver:
- * Copyright (C) 1998 - 2005 Douglas Gilbert
+ * Copyright (C) 1998 - 2010 Douglas Gilbert
*
* Modified 19-JAN-1998 Richard Gooch <rgooch@xxxxxxxxxxxxx> Devfs support
*
@@ -18,8 +18,8 @@
*
*/
-static int sg_version_num = 30534; /* 2 digits for each component */
-#define SG_VERSION_STR "3.5.34"
+static int sg_version_num = 30535; /* 2 digits for each component */
+#define SG_VERSION_STR "3.5.35"
/*
* D. P. Gilbert (dgilbert@xxxxxxxxxxxx, dougg@xxxxxxxxxxxxx), notes:
@@ -61,7 +61,7 @@ static int sg_version_num = 30534; /* 2
#ifdef CONFIG_SCSI_PROC_FS
#include <linux/proc_fs.h>
-static char *sg_version_date = "20061027";
+static char *sg_version_date = "20100323";
static int sg_proc_init(void);
static void sg_proc_cleanup(void);
@@ -710,8 +710,15 @@ sg_common_write(Sg_fd * sfp, Sg_request
int k, data_dir;
Sg_device *sdp = sfp->parentdp;
sg_io_hdr_t *hp = &srp->header;
+ int at_head = 1; /* current default: Q_AT_HEAD */
srp->data.cmd_opcode = cmnd[0]; /* hold opcode of command */
+ if ('\0' != hp->interface_id) { /* old interface misuses flags */
+ if (SG_FLAG_Q_AT_TAIL & hp->flags)
+ at_head = 0;
+ if (SG_FLAG_Q_AT_HEAD & hp->flags)
+ at_head = 1;
+ }
hp->status = 0;
hp->masked_status = 0;
hp->msg_status = 0;
@@ -753,7 +760,7 @@ sg_common_write(Sg_fd * sfp, Sg_request
srp->rq->timeout = timeout;
kref_get(&sfp->f_ref); /* sg_rq_end_io() does kref_put(). */
blk_execute_rq_nowait(sdp->device->request_queue, sdp->disk,
- srp->rq, 1, sg_rq_end_io);
+ srp->rq, at_head, sg_rq_end_io);
return 0;
}
--- linux/block/scsi_ioctl.c 2010-02-26 12:27:51.000000000 -0500
+++ linux/block/scsi_ioctl.c2633qat2 2010-03-23 21:15:40.000000000 -0400
@@ -288,11 +288,16 @@ static int sg_io(struct request_queue *q
struct request *rq;
char sense[SCSI_SENSE_BUFFERSIZE];
struct bio *bio;
+ int at_head = 0; /* existing default was q_at_tail */
if (hdr->interface_id != 'S')
return -EINVAL;
if (hdr->cmd_len > BLK_MAX_CDB)
return -EINVAL;
+ if (hdr->flags & SG_FLAG_Q_AT_HEAD)
+ at_head = 1;
+ if (hdr->flags & SG_FLAG_Q_AT_TAIL)
+ at_head = 0;
if (hdr->dxfer_len > (queue_max_hw_sectors(q) << 9))
return -EIO;
@@ -367,7 +372,7 @@ static int sg_io(struct request_queue *q
* (if he doesn't check that is his problem).
* N.B. a non-zero SCSI status is _not_ necessarily an error.
*/
- blk_execute_rq(q, bd_disk, rq, 0);
+ blk_execute_rq(q, bd_disk, rq, at_head);
hdr->duration = jiffies_to_msecs(jiffies - start_time);
