Hi,
在 2024/04/18 13:44, tada keisuke 写道:
This patch depends on patch 07.
All rdevs running in RAID 1/10 switch nr_pending to atomic mode.
The value of nr_pending is read in a normal operation (choose_best_rdev()).
Therefore, nr_pending must always be consistent.
Signed-off-by: Keisuke TADA <keisuke1.tada@xxxxxxxxxx>
Signed-off-by: Toshifumi OHTAKE <toshifumi.ootake@xxxxxxxxxx>
---
drivers/md/md.h | 14 ++++++++++++++
drivers/md/raid1.c | 7 +++++++
drivers/md/raid10.c | 4 ++++
3 files changed, 25 insertions(+)
diff --git a/drivers/md/md.h b/drivers/md/md.h
index ab09e312c9bb..57b09b567ffa 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -236,6 +236,20 @@ static inline unsigned long nr_pending_read(struct md_rdev *rdev)
return atomic_long_read(&rdev->nr_pending.data->count);
}
+static inline bool nr_pending_is_percpu_mode(struct md_rdev *rdev)
+{
+ unsigned long __percpu *percpu_count;
+
+ return __ref_is_percpu(&rdev->nr_pending, &percpu_count);
+}
+
+static inline bool nr_pending_is_atomic_mode(struct md_rdev *rdev)
+{
+ unsigned long __percpu *percpu_count;
+
+ return !__ref_is_percpu(&rdev->nr_pending, &percpu_count);
+}
+
static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
sector_t *first_bad, int *bad_sectors)
{
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 12318fb15a88..c38ae13aadab 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -784,6 +784,7 @@ static int choose_best_rdev(struct r1conf *conf, struct r1bio *r1_bio)
if (ctl.readable_disks++ == 1)
set_bit(R1BIO_FailFast, &r1_bio->state);
+ WARN_ON_ONCE(nr_pending_is_percpu_mode(rdev));
pending = nr_pending_read(rdev);
dist = abs(r1_bio->sector - conf->mirrors[disk].head_position);
@@ -1930,6 +1931,7 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
if (err)
return err;
+ percpu_ref_switch_to_atomic_sync(&rdev->nr_pending);
raid1_add_conf(conf, rdev, mirror, false);
/* As all devices are equivalent, we don't need a full recovery
* if this was recently any drive of the array
@@ -1949,6 +1951,7 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
set_bit(Replacement, &rdev->flags);
raid1_add_conf(conf, rdev, repl_slot, true);
err = 0;
+ percpu_ref_switch_to_atomic_sync(&rdev->nr_pending);
I don't understand what's the point here, 'nr_pending' will be used when
the rdev issuing IO, and it's always used as atomic mode, there is no
difference.
Consider that 'nr_pending' must be read from IO fast path, use it as
atomic is something we must accept. Unless someone comes up with a plan
to avoid reading 'inflight' counter from fast path like generic block
layer, it's not ok to me to switch to percpu_ref for now.
+CC Paul
HI, Paul, perhaps you RR mode doesn't need such 'inflight' counter
anymore?
Thanks,
Kuai
conf->fullsync = 1;
}
@@ -3208,6 +3211,7 @@ static void raid1_free(struct mddev *mddev, void *priv);
static int raid1_run(struct mddev *mddev)
{
struct r1conf *conf;
+ struct md_rdev *rdev;
int i;
int ret;
@@ -3269,6 +3273,9 @@ static int raid1_run(struct mddev *mddev)
/*
* Ok, everything is just fine now
*/
+ rdev_for_each(rdev, mddev) {
+ percpu_ref_switch_to_atomic_sync(&rdev->nr_pending);
+ }
rcu_assign_pointer(mddev->thread, conf->thread);
rcu_assign_pointer(conf->thread, NULL);
mddev->private = conf;
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index b91dd6c0be5a..66896a1076e1 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -808,6 +808,7 @@ static struct md_rdev *read_balance(struct r10conf *conf,
nonrot = bdev_nonrot(rdev->bdev);
has_nonrot_disk |= nonrot;
+ WARN_ON_ONCE(nr_pending_is_percpu_mode(rdev));
pending = nr_pending_read(rdev);
if (min_pending > pending && nonrot) {
min_pending = pending;
@@ -2113,6 +2114,7 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
p->recovery_disabled = mddev->recovery_disabled - 1;
rdev->raid_disk = mirror;
err = 0;
+ percpu_ref_switch_to_atomic_sync(&rdev->nr_pending);
if (rdev->saved_raid_disk != mirror)
conf->fullsync = 1;
WRITE_ONCE(p->rdev, rdev);
@@ -2127,6 +2129,7 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
err = mddev_stack_new_rdev(mddev, rdev);
if (err)
return err;
+ percpu_ref_switch_to_atomic_sync(&rdev->nr_pending);
conf->fullsync = 1;
WRITE_ONCE(p->replacement, rdev);
}
@@ -4028,6 +4031,7 @@ static int raid10_run(struct mddev *mddev)
rdev_for_each(rdev, mddev) {
long long diff;
+ percpu_ref_switch_to_atomic_sync(&rdev->nr_pending);
disk_idx = rdev->raid_disk;
if (disk_idx < 0)
continue;
