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authorMikulas Patocka <mpatocka@redhat.com>2018-11-06 22:34:59 +0100
committerMike Snitzer <snitzer@redhat.com>2018-12-18 09:02:25 -0500
commit24113d4878439baf1f23c1a33dfcc340fba66e97 (patch)
tree8a5111ada71d026b290b7c009e79b28c99fbcdf5 /drivers/md
parentcd19181bf9ad4b7f40f2a4e0355d052109c76529 (diff)
dm: avoid indirect call in __dm_make_request
Indirect calls are inefficient because of retpolines that are used for spectre workaround. This patch replaces an indirect call with a condition (that can be predicted by the branch predictor). Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm.c29
1 files changed, 6 insertions, 23 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index dddbca63e140..fa70c90e6757 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1696,10 +1696,7 @@ out:
return ret;
}
-typedef blk_qc_t (process_bio_fn)(struct mapped_device *, struct dm_table *, struct bio *);
-
-static blk_qc_t __dm_make_request(struct request_queue *q, struct bio *bio,
- process_bio_fn process_bio)
+static blk_qc_t dm_make_request(struct request_queue *q, struct bio *bio)
{
struct mapped_device *md = q->queuedata;
blk_qc_t ret = BLK_QC_T_NONE;
@@ -1719,26 +1716,15 @@ static blk_qc_t __dm_make_request(struct request_queue *q, struct bio *bio,
return ret;
}
- ret = process_bio(md, map, bio);
+ if (dm_get_md_type(md) == DM_TYPE_NVME_BIO_BASED)
+ ret = __process_bio(md, map, bio);
+ else
+ ret = __split_and_process_bio(md, map, bio);
dm_put_live_table(md, srcu_idx);
return ret;
}
-/*
- * The request function that remaps the bio to one target and
- * splits off any remainder.
- */
-static blk_qc_t dm_make_request(struct request_queue *q, struct bio *bio)
-{
- return __dm_make_request(q, bio, __split_and_process_bio);
-}
-
-static blk_qc_t dm_make_request_nvme(struct request_queue *q, struct bio *bio)
-{
- return __dm_make_request(q, bio, __process_bio);
-}
-
static int dm_any_congested(void *congested_data, int bdi_bits)
{
int r = bdi_bits;
@@ -2229,12 +2215,9 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t)
break;
case DM_TYPE_BIO_BASED:
case DM_TYPE_DAX_BIO_BASED:
- dm_init_normal_md_queue(md);
- blk_queue_make_request(md->queue, dm_make_request);
- break;
case DM_TYPE_NVME_BIO_BASED:
dm_init_normal_md_queue(md);
- blk_queue_make_request(md->queue, dm_make_request_nvme);
+ blk_queue_make_request(md->queue, dm_make_request);
break;
case DM_TYPE_NONE:
WARN_ON_ONCE(true);