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| author | Boaz Harrosh <bharrosh@panasas.com> | 2011-01-23 17:53:24 +0200 |
|---|---|---|
| committer | James Bottomley <James.Bottomley@suse.de> | 2011-01-24 12:06:31 -0600 |
| commit | 4977c82504f58d7579acabd21688183eaa8768fb (patch) | |
| tree | fc455d2fe5f925b6cb1c143231c56b76befae373 | |
| parent | 1e34c8387380269b9d7707d625aeb9e9e92233f0 (diff) | |
| download | blackbird-op-linux-4977c82504f58d7579acabd21688183eaa8768fb.tar.gz blackbird-op-linux-4977c82504f58d7579acabd21688183eaa8768fb.zip | |
[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>
| -rw-r--r-- | drivers/scsi/osd/osd_initiator.c | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/drivers/scsi/osd/osd_initiator.c b/drivers/scsi/osd/osd_initiator.c index b37c8a3c1bb0..86afb13f1e79 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; } |
