From 4977c82504f58d7579acabd21688183eaa8768fb Mon Sep 17 00:00:00 2001 From: Boaz Harrosh Date: Sun, 23 Jan 2011 17:53:24 +0200 Subject: [PATCH] [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 Signed-off-by: James Bottomley --- drivers/scsi/osd/osd_initiator.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) 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 @@ int osd_req_read_sg(struct osd_request *or, 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; } -- 2.7.4