[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/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d5e77e9..681ed1b 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -64,6 +64,8 @@
};
#undef SP
+static struct kmem_cache *scsi_bidi_sdb_cache;
+
static void scsi_run_queue(struct request_queue *q);
/*
@@ -790,10 +792,38 @@
scsi_free_sgtable(&cmd->sdb);
memset(&cmd->sdb, 0, sizeof(cmd->sdb));
+
+ if (scsi_bidi_cmnd(cmd)) {
+ struct scsi_data_buffer *bidi_sdb =
+ cmd->request->next_rq->special;
+ scsi_free_sgtable(bidi_sdb);
+ kmem_cache_free(scsi_bidi_sdb_cache, bidi_sdb);
+ cmd->request->next_rq->special = NULL;
+ }
}
EXPORT_SYMBOL(scsi_release_buffers);
/*
+ * Bidi commands Must be complete as a whole, both sides at once.
+ * If part of the bytes were written and lld returned
+ * scsi_in()->resid and/or scsi_out()->resid this information will be left
+ * in req->data_len and req->next_rq->data_len. The upper-layer driver can
+ * decide what to do with this information.
+ */
+void scsi_end_bidi_request(struct scsi_cmnd *cmd)
+{
+ blk_end_bidi_request(cmd->request, 0, scsi_out(cmd)->resid,
+ scsi_in(cmd)->resid);
+ scsi_release_buffers(cmd);
+
+ /*
+ * This will goose the queue request function at the end, so we don't
+ * need to worry about launching another command.
+ */
+ scsi_next_command(cmd);
+}
+
+/*
* Function: scsi_io_completion()
*
* Purpose: Completion processing for block device I/O requests.
@@ -854,9 +884,15 @@
req->sense_len = len;
}
}
+ if (scsi_bidi_cmnd(cmd)) {
+ /* will also release_buffers */
+ scsi_end_bidi_request(cmd);
+ return;
+ }
req->data_len = scsi_get_resid(cmd);
}
+ BUG_ON(blk_bidi_rq(req)); /* bidi not support for !blk_pc_request yet */
scsi_release_buffers(cmd);
/*
@@ -982,28 +1018,16 @@
scsi_end_request(cmd, -EIO, this_count, !result);
}
-/*
- * Function: scsi_init_io()
- *
- * Purpose: SCSI I/O initialize function.
- *
- * Arguments: cmd - Command descriptor we wish to initialize
- *
- * Returns: 0 on success
- * BLKPREP_DEFER if the failure is retryable
- */
-int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
+static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
+ gfp_t gfp_mask)
{
- struct request *req = cmd->request;
- int count;
- struct scsi_data_buffer *sdb = &cmd->sdb;
+ int count;
/*
* If sg table allocation fails, requeue request later.
*/
if (unlikely(scsi_alloc_sgtable(sdb, req->nr_phys_segments,
gfp_mask))) {
- scsi_unprep_request(req);
return BLKPREP_DEFER;
}
@@ -1022,6 +1046,50 @@
sdb->table.nents = count;
return BLKPREP_OK;
}
+
+/*
+ * Function: scsi_init_io()
+ *
+ * Purpose: SCSI I/O initialize function.
+ *
+ * Arguments: cmd - Command descriptor we wish to initialize
+ *
+ * Returns: 0 on success
+ * BLKPREP_DEFER if the failure is retryable
+ * BLKPREP_KILL if the failure is fatal
+ */
+int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
+{
+ int error = scsi_init_sgtable(cmd->request, &cmd->sdb, gfp_mask);
+ if (error)
+ goto err_exit;
+
+ if (blk_bidi_rq(cmd->request)) {
+ struct scsi_data_buffer *bidi_sdb = kmem_cache_zalloc(
+ scsi_bidi_sdb_cache, GFP_ATOMIC);
+ if (!bidi_sdb) {
+ error = BLKPREP_DEFER;
+ goto err_exit;
+ }
+
+ cmd->request->next_rq->special = bidi_sdb;
+ error = scsi_init_sgtable(cmd->request->next_rq, bidi_sdb,
+ GFP_ATOMIC);
+ if (error)
+ goto err_exit;
+ }
+
+ return BLKPREP_OK ;
+
+err_exit:
+ scsi_release_buffers(cmd);
+ if (error == BLKPREP_KILL)
+ scsi_put_command(cmd);
+ else /* BLKPREP_DEFER */
+ scsi_unprep_request(cmd->request);
+
+ return error;
+}
EXPORT_SYMBOL(scsi_init_io);
static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
@@ -1639,6 +1707,14 @@
return -ENOMEM;
}
+ scsi_bidi_sdb_cache = kmem_cache_create("scsi_bidi_sdb",
+ sizeof(struct scsi_data_buffer),
+ 0, 0, NULL);
+ if (!scsi_bidi_sdb_cache) {
+ printk(KERN_ERR "SCSI: can't init scsi bidi sdb cache\n");
+ return -ENOMEM;
+ }
+
for (i = 0; i < SG_MEMPOOL_NR; i++) {
struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
int size = sgp->size * sizeof(struct scatterlist);
