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Subject[PATCH][RFC 12/23]: Patch to add necessary support for SCST pass-through
This patch adds to the kernel new function scsi_execute_async_fifo(). 
This function is the same as scsi_execute_async(), but it queues
requests in FIFO order, not LIFO as scsi_execute_async() does.

Function scsi_execute_async_fifo() is needed for SCST to queue commands
from remote initiators to SCST devices in pass-through mode. There is no
simple alternative to this function, because SCST has to deal with SG
vectors and can't deal with bio's. Hardware target drivers require that.

Signed-off-by: Vladislav Bolkhovitin <vst@vlnb.net>
---
drivers/scsi/scsi_lib.c | 58 +++++++++++++++++++++++++++++++++++++++++----
include/scsi/scsi_device.h | 8 ++++++
2 files changed, 62 insertions(+), 4 deletions(-)

diff -upr linux-2.6.26/drivers/scsi/scsi_lib.c linux-2.6.26/drivers/scsi/scsi_lib.c
--- linux-2.6.26/drivers/scsi/scsi_lib.c 2008-07-14 01:51:29.000000000 +0400
+++ linux-2.6.26/drivers/scsi/scsi_lib.c 2008-07-31 21:20:00.000000000 +0400
@@ -372,7 +372,7 @@ free_bios:
}

/**
- * scsi_execute_async - insert request
+ * __scsi_execute_async - insert request
* @sdev: scsi device
* @cmd: scsi command
* @cmd_len: length of scsi cdb
@@ -385,11 +385,14 @@ free_bios:
* @privdata: data passed to done()
* @done: callback function when done
* @gfp: memory allocation flags
+ * @at_head: insert request at head or tail of queue
*/
-int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
+static inline int __scsi_execute_async(struct scsi_device *sdev,
+ const unsigned char *cmd,
int cmd_len, int data_direction, void *buffer, unsigned bufflen,
int use_sg, int timeout, int retries, void *privdata,
- void (*done)(void *, char *, int, int), gfp_t gfp)
+ void (*done)(void *, char *, int, int), gfp_t gfp,
+ int at_head)
{
struct request *req;
struct scsi_io_context *sioc;
@@ -426,7 +429,7 @@ int scsi_execute_async(struct scsi_devic
sioc->data = privdata;
sioc->done = done;

- blk_execute_rq_nowait(req->q, NULL, req, 1, scsi_end_async);
+ blk_execute_rq_nowait(req->q, NULL, req, at_head, scsi_end_async);
return 0;

free_req:
@@ -435,8 +438,55 @@ free_sense:
kmem_cache_free(scsi_io_context_cache, sioc);
return DRIVER_ERROR << 24;
}
+
+/**
+ * scsi_execute_async - insert request
+ * @sdev: scsi device
+ * @cmd: scsi command
+ * @cmd_len: length of scsi cdb
+ * @data_direction: data direction
+ * @buffer: data buffer (this can be a kernel buffer or scatterlist)
+ * @bufflen: len of buffer
+ * @use_sg: if buffer is a scatterlist this is the number of elements
+ * @timeout: request timeout in seconds
+ * @retries: number of times to retry request
+ * @flags: or into request flags
+ **/
+int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
+ int cmd_len, int data_direction, void *buffer,
+ unsigned bufflen, int use_sg, int timeout,
+ int retries, void *privdata,
+ void (*done)(void *, char *, int, int), gfp_t gfp)
+{
+ return __scsi_execute_async(sdev, cmd, cmd_len, data_direction, buffer,
+ bufflen, use_sg, timeout, retries, privdata, done, gfp, 1);
+}
EXPORT_SYMBOL_GPL(scsi_execute_async);

+/**
+ * scsi_execute_async_fifo - insert request at tail, in FIFO order
+ * @sdev: scsi device
+ * @cmd: scsi command
+ * @cmd_len: length of scsi cdb
+ * @data_direction: data direction
+ * @buffer: data buffer (this can be a kernel buffer or scatterlist)
+ * @bufflen: len of buffer
+ * @use_sg: if buffer is a scatterlist this is the number of elements
+ * @timeout: request timeout in seconds
+ * @retries: number of times to retry request
+ * @flags: or into request flags
+ **/
+int scsi_execute_async_fifo(struct scsi_device *sdev, const unsigned char *cmd,
+ int cmd_len, int data_direction, void *buffer,
+ unsigned bufflen, int use_sg, int timeout, int retries,
+ void *privdata,
+ void (*done)(void *, char *, int, int), gfp_t gfp)
+{
+ return __scsi_execute_async(sdev, cmd, cmd_len, data_direction, buffer,
+ bufflen, use_sg, timeout, retries, privdata, done, gfp, 0);
+}
+EXPORT_SYMBOL_GPL(scsi_execute_async_fifo);
+
/*
* Function: scsi_init_cmd_errh()
*
diff -upr linux-2.6.26/include/scsi/scsi_device.h linux-2.6.26/include/scsi/scsi_device.h
--- linux-2.6.26/include/scsi/scsi_device.h 2008-07-14 01:51:29.000000000 +0400
+++ linux-2.6.26/include/scsi/scsi_device.h 2008-07-31 21:20:39.000000000 +0400
@@ -365,6 +365,14 @@ extern int scsi_execute_async(struct scs
int timeout, int retries, void *privdata,
void (*done)(void *, char *, int, int),
gfp_t gfp);
+#define SCSI_EXEC_REQ_FIFO_DEFINED
+extern int scsi_execute_async_fifo(struct scsi_device *sdev,
+ const unsigned char *cmd, int cmd_len,
+ int data_direction, void *buffer,
+ unsigned bufflen, int use_sg,
+ int timeout, int retries, void *privdata,
+ void (*done)(void *, char *, int, int),
+ gfp_t gfp);

static inline int __must_check scsi_device_reprobe(struct scsi_device *sdev)
{



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