[PATCH v1 3/7] md: raid1: handle bi_rw_hint accordingly

Allison Henderson
2018-11-28T03:53:17Z

From: Bob Liu <bob.liu@oracle.com>

* nr_mirrors that raid1 device support should be @raid_disks, init it properly.
* Recording i/o went to which mirror in bio->bi_rw_hint.
* Read from specific real device if bi_rw_hint was set.

Todo:
* Support more drivers.

Signed-off-by: Bob Liu <bob.liu@oracle.com>
---
drivers/md/raid1.c | 31 ++++++++++++++++++++++++++++---
1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index fedf8c0..d2bdd0e 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -553,7 +553,8 @@ static sector_t align_to_barrier_unit_end(sector_t start_sector,
*
* The rdev for the device selected will have nr_pending incremented.
*/
-static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sectors)
+static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sectors,
+ unsigned short disk_hint)
{
const sector_t this_sector = r1_bio->sector;
int sectors;
@@ -566,6 +567,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
struct md_rdev *rdev;
int choose_first;
int choose_next_idle;
+ int max_disks;

rcu_read_lock();
/*
@@ -593,7 +595,20 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
else
choose_first = 0;

- for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
+ if (disk_hint) {
+ disk = disk_hint - 1;
+ /*
+ * Consider replacement as a special case, use original device to
+ * indicate which mirror this i/o was happened.
+ */
+ if (disk >= conf->raid_disks)
+ disk -= conf->raid_disks;
+ max_disks = disk + 1;
+ } else {
+ disk = 0;
+ max_disks = conf->raid_disks * 2;
+ }
+ for (; disk < max_disks; disk++) {
sector_t dist;
sector_t first_bad;
int bad_sectors;
@@ -1234,7 +1249,7 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
* make_request() can abort the operation when read-ahead is being
* used and no empty request is available.
*/
- rdisk = read_balance(conf, r1_bio, &max_sectors);
+ rdisk = read_balance(conf, r1_bio, &max_sectors, bio->bi_rw_hint);

if (rdisk < 0) {
/* couldn't find anywhere to read from */
@@ -1247,6 +1262,10 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
raid_end_bio_io(r1_bio);
return;
}
+
+ /* Recording i/o went to which real device. */
+ bio->bi_rw_hint = rdisk;
+
mirror = conf->mirrors + rdisk;

if (print_msg)
@@ -1279,6 +1298,11 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
r1_bio->read_disk = rdisk;

read_bio = bio_clone_fast(bio, gfp, &mddev->bio_set);
+ /*
+ * Clear bi_rw_hint, because it was set last i/o went to which real
+ * device.
+ */
+ read_bio->bi_rw_hint = 0;

r1_bio->bios[rdisk] = read_bio;

@@ -3078,6 +3102,7 @@ static int raid1_run(struct mddev *mddev)
if (mddev->queue) {
blk_queue_max_write_same_sectors(mddev->queue, 0);
blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
+ blk_queue_set_mirrors(mddev->queue, mddev->raid_disks);
}

rdev_for_each(rdev, mddev) {
--
2.7.4