[SCSI] libosd: osd_req_read_sg, optimize the single entry case
Since sg-read is a bidi operation, it is a gain to convert
a single sg entry into a regular read. Better do this in the
generic layer then force each caller to do so.
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
diff --git a/drivers/scsi/osd/osd_initiator.c b/drivers/scsi/osd/osd_initiator.c
index b37c8a3..86afb13f 100644
--- a/drivers/scsi/osd/osd_initiator.c
+++ b/drivers/scsi/osd/osd_initiator.c
@@ -1005,11 +1005,23 @@
const struct osd_sg_entry *sglist, unsigned numentries)
{
u64 len;
- int ret = _add_sg_continuation_descriptor(or, sglist, numentries, &len);
+ u64 off;
+ int ret;
- if (ret)
- return ret;
- osd_req_read(or, obj, 0, bio, len);
+ if (numentries > 1) {
+ off = 0;
+ ret = _add_sg_continuation_descriptor(or, sglist, numentries,
+ &len);
+ if (ret)
+ return ret;
+ } else {
+ /* Optimize the case of single segment, read_sg is a
+ * bidi operation.
+ */
+ len = sglist->len;
+ off = sglist->offset;
+ }
+ osd_req_read(or, obj, off, bio, len);
return 0;
}