[PATCH md-6.9 02/10] md: record nonrot rdevs while adding/removing rdevs to conf

[Yu Kuai]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

For raid1/raid10, each read will iterate all the rdevs from conf and
check if any rdev is non-rotational, then choose rdev with minimal IO
inflight if so, or rdev with closest distance otherwise.

Disk nonrot info can be changed through sysfs entry:

/sys/block/[disk_name]/queue/rotational

However, consider that this should only be used for testing, and user
really shouldn't do this in real life. Record the number of non-rotational
disks in mddev, to avoid checking each rdev in IO fast path and simplify
read_balance() a little bit.

Co-developed-by: Paul Luse <paul.e.luse@xxxxxxxxxxxxxxx>
Signed-off-by: Paul Luse <paul.e.luse@xxxxxxxxxxxxxxx>
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 drivers/md/md.c     | 28 ++++++++++++++++++++++++++--
 drivers/md/md.h     |  2 ++
 drivers/md/raid1.c  |  9 ++-------
 drivers/md/raid10.c |  8 ++------
 4 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index e2a5f513dbb7..9e671eec9309 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -146,6 +146,24 @@ static inline int speed_max(struct mddev *mddev)
 		mddev->sync_speed_max : sysctl_speed_limit_max;
 }
 
+static void rdev_update_nonrot(struct md_rdev *rdev)
+{
+	if (!bdev_nonrot(rdev->bdev))
+		return;
+
+	set_bit(Nonrot, &rdev->flags);
+	WRITE_ONCE(rdev->mddev->nonrot_disks, rdev->mddev->nonrot_disks + 1);
+}
+
+static void rdev_clear_nonrot(struct md_rdev *rdev)
+{
+	if (!test_bit(Nonrot, &rdev->flags))
+		return;
+
+	clear_bit(Nonrot, &rdev->flags);
+	WRITE_ONCE(rdev->mddev->nonrot_disks, rdev->mddev->nonrot_disks - 1);
+}
+
 static void rdev_uninit_serial(struct md_rdev *rdev)
 {
 	if (!test_and_clear_bit(CollisionCheck, &rdev->flags))
@@ -2922,6 +2940,8 @@ static int add_bound_rdev(struct md_rdev *rdev)
 			md_kick_rdev_from_array(rdev);
 			return err;
 		}
+
+		rdev_update_nonrot(rdev);
 	}
 	sysfs_notify_dirent_safe(rdev->sysfs_state);
 
@@ -3271,8 +3291,10 @@ slot_store(struct md_rdev *rdev, const char *buf, size_t len)
 		if (err) {
 			rdev->raid_disk = -1;
 			return err;
-		} else
-			sysfs_notify_dirent_safe(rdev->sysfs_state);
+		}
+
+		rdev_update_nonrot(rdev);
+		sysfs_notify_dirent_safe(rdev->sysfs_state);
 		/* failure here is OK */;
 		sysfs_link_rdev(rdev->mddev, rdev);
 		/* don't wakeup anyone, leave that to userspace. */
@@ -9266,6 +9288,7 @@ static int remove_and_add_spares(struct mddev *mddev,
 	rdev_for_each(rdev, mddev) {
 		if ((this == NULL || rdev == this) && rdev_removeable(rdev) &&
 		    !mddev->pers->hot_remove_disk(mddev, rdev)) {
+			rdev_clear_nonrot(rdev);
 			sysfs_unlink_rdev(mddev, rdev);
 			rdev->saved_raid_disk = rdev->raid_disk;
 			rdev->raid_disk = -1;
@@ -9289,6 +9312,7 @@ static int remove_and_add_spares(struct mddev *mddev,
 		if (!test_bit(Journal, &rdev->flags))
 			rdev->recovery_offset = 0;
 		if (mddev->pers->hot_add_disk(mddev, rdev) == 0) {
+			rdev_update_nonrot(rdev);
 			/* failure here is OK */
 			sysfs_link_rdev(mddev, rdev);
 			if (!test_bit(Journal, &rdev->flags))
diff --git a/drivers/md/md.h b/drivers/md/md.h
index a49ab04ab707..54aa951f2bba 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -207,6 +207,7 @@ enum flag_bits {
 				 * check if there is collision between raid1
 				 * serial bios.
 				 */
+	Nonrot,			/* non-rotational device (SSD) */
 };
 
 static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
@@ -312,6 +313,7 @@ struct mddev {
 	unsigned long			flags;
 	unsigned long			sb_flags;
 
+	int				nonrot_disks;
 	int				suspended;
 	struct mutex			suspend_mutex;
 	struct percpu_ref		active_io;
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index a145fe48b9ce..c60ea58ae8c5 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -599,7 +599,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 	int sectors;
 	int best_good_sectors;
 	int best_disk, best_dist_disk, best_pending_disk;
-	int has_nonrot_disk;
 	int disk;
 	sector_t best_dist;
 	unsigned int min_pending;
@@ -620,7 +619,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 	best_pending_disk = -1;
 	min_pending = UINT_MAX;
 	best_good_sectors = 0;
-	has_nonrot_disk = 0;
 	choose_next_idle = 0;
 	clear_bit(R1BIO_FailFast, &r1_bio->state);
 
@@ -637,7 +635,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 		sector_t first_bad;
 		int bad_sectors;
 		unsigned int pending;
-		bool nonrot;
 
 		rdev = conf->mirrors[disk].rdev;
 		if (r1_bio->bios[disk] == IO_BLOCKED
@@ -703,8 +700,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 			/* At least two disks to choose from so failfast is OK */
 			set_bit(R1BIO_FailFast, &r1_bio->state);
 
-		nonrot = bdev_nonrot(rdev->bdev);
-		has_nonrot_disk |= nonrot;
 		pending = atomic_read(&rdev->nr_pending);
 		dist = abs(this_sector - conf->mirrors[disk].head_position);
 		if (choose_first) {
@@ -731,7 +726,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 			 * small, but not a big deal since when the second disk
 			 * starts IO, the first disk is likely still busy.
 			 */
-			if (nonrot && opt_iosize > 0 &&
+			if (test_bit(Nonrot, &rdev->flags) && opt_iosize > 0 &&
 			    mirror->seq_start != MaxSector &&
 			    mirror->next_seq_sect > opt_iosize &&
 			    mirror->next_seq_sect - opt_iosize >=
@@ -763,7 +758,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 	 * mixed ratation/non-rotational disks depending on workload.
 	 */
 	if (best_disk == -1) {
-		if (has_nonrot_disk || min_pending == 0)
+		if (conf->mddev->nonrot_disks || min_pending == 0)
 			best_disk = best_pending_disk;
 		else
 			best_disk = best_dist_disk;
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index d5a7a621f0f0..1f6693e40e12 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -735,7 +735,6 @@ static struct md_rdev *read_balance(struct r10conf *conf,
 	struct md_rdev *best_dist_rdev, *best_pending_rdev, *rdev = NULL;
 	int do_balance;
 	int best_dist_slot, best_pending_slot;
-	bool has_nonrot_disk = false;
 	unsigned int min_pending;
 	struct geom *geo = &conf->geo;
 
@@ -766,7 +765,6 @@ static struct md_rdev *read_balance(struct r10conf *conf,
 		int bad_sectors;
 		sector_t dev_sector;
 		unsigned int pending;
-		bool nonrot;
 
 		if (r10_bio->devs[slot].bio == IO_BLOCKED)
 			continue;
@@ -818,10 +816,8 @@ static struct md_rdev *read_balance(struct r10conf *conf,
 		if (!do_balance)
 			break;
 
-		nonrot = bdev_nonrot(rdev->bdev);
-		has_nonrot_disk |= nonrot;
 		pending = atomic_read(&rdev->nr_pending);
-		if (min_pending > pending && nonrot) {
+		if (min_pending > pending && test_bit(Nonrot, &rdev->flags)) {
 			min_pending = pending;
 			best_pending_slot = slot;
 			best_pending_rdev = rdev;
@@ -851,7 +847,7 @@ static struct md_rdev *read_balance(struct r10conf *conf,
 		}
 	}
 	if (slot >= conf->copies) {
-		if (has_nonrot_disk) {
+		if (conf->mddev->nonrot_disks) {
 			slot = best_pending_slot;
 			rdev = best_pending_rdev;
 		} else {
-- 
2.39.2