[SCSI] bidirectional command support
At the block level bidi request uses req->next_rq pointer for a second
bidi_read request.
At Scsi-midlayer a second scsi_data_buffer structure is used for the
bidi_read part. This bidi scsi_data_buffer is put on
request->next_rq->special. Struct scsi_cmnd is not changed.
- Define scsi_bidi_cmnd() to return true if it is a bidi request and a
second sgtable was allocated.
- Define scsi_in()/scsi_out() to return the in or out scsi_data_buffer
from this command This API is to isolate users from the mechanics of
bidi.
- Define scsi_end_bidi_request() to do what scsi_end_request() does but
for a bidi request. This is necessary because bidi commands are a bit
tricky here. (See comments in body)
- scsi_release_buffers() will also release the bidi_read scsi_data_buffer
- scsi_io_completion() on bidi commands will now call
scsi_end_bidi_request() and return.
- The previous work done in scsi_init_io() is now done in a new
scsi_init_sgtable() (which is 99% identical to old scsi_init_io())
The new scsi_init_io() will call the above twice if needed also for
the bidi_read command. Only at this point is a command bidi.
- In scsi_error.c at scsi_eh_prep/restore_cmnd() make sure bidi-lld is not
confused by a get-sense command that looks like bidi. This is done
by puting NULL at request->next_rq, and restoring.
[jejb: update to sg_table and resolve conflicts
also update to blk-end-request and resolve conflicts]
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index c6478bb..de28aab 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -2,12 +2,12 @@
#define _SCSI_SCSI_CMND_H
#include <linux/dma-mapping.h>
+#include <linux/blkdev.h>
#include <linux/list.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/scatterlist.h>
-struct request;
struct Scsi_Host;
struct scsi_device;
@@ -158,4 +158,21 @@
#define scsi_for_each_sg(cmd, sg, nseg, __i) \
for_each_sg(scsi_sglist(cmd), sg, nseg, __i)
+static inline int scsi_bidi_cmnd(struct scsi_cmnd *cmd)
+{
+ return blk_bidi_rq(cmd->request) &&
+ (cmd->request->next_rq->special != NULL);
+}
+
+static inline struct scsi_data_buffer *scsi_in(struct scsi_cmnd *cmd)
+{
+ return scsi_bidi_cmnd(cmd) ?
+ cmd->request->next_rq->special : &cmd->sdb;
+}
+
+static inline struct scsi_data_buffer *scsi_out(struct scsi_cmnd *cmd)
+{
+ return &cmd->sdb;
+}
+
#endif /* _SCSI_SCSI_CMND_H */