>
>Hi,
> sorry for the excessive delay in reviewing these.
>
> I've applied the first three, though I fixed some careless spelling errors in
> the patch descriptions and fixed up some of the grammar.
>
> This one is fairly good - just a couple of fixes needed.
> It is good that you have a nice details patch description at the top, but it
> is a bit hard to read. Fixing the spelling and improving the formatting
> would help a lot....
>
> See below for comments in the code....
>
[snip]
> ...
>
>
>> wait_event_lock_irq(conf->wait_barrier,
>> !conf->array_frozen &&
>> - !conf->nr_pending && conf->barrier < RESYNC_DEPTH,
>> + !conf->nr_pending && conf->barrier < RESYNC_DEPTH &&
>> + (conf->next_resync + RESYNC_SECTORS
>> + <= conf->start_next_window),
>
>I think conditions are much more readable if the thing that you expect to
>change comes first.
>In this case we might need to wait until start_next_window increases, so
> conf->start_next_window >= conf->next_resync + RESYNC_SECTORS
>
>as it is, it looks like you are waiting for next_resync to decrease.
>
>
>> conf->resync_lock);
>>
>> spin_unlock_irq(&conf->resync_lock);
>> @@ -846,10 +863,43 @@ static void lower_barrier(struct r1conf *conf)
>> wake_up(&conf->wait_barrier);
>> }
>>
>> -static void wait_barrier(struct r1conf *conf)
>> +static bool need_to_wait_for_sync(struct r1conf *conf, struct bio *bio)
>> {
>> + bool wait = false;
>> +
>> + if (conf->array_frozen || !bio)
>> + wait = true;
>> + else if (conf->barrier && bio_data_dir(bio) == WRITE) {
>> + if (conf->next_resync < RESYNC_WINDOW_SECTORS)
>> + wait = true;
>> + else if (conf->next_resync - RESYNC_WINDOW_SECTORS >=
>> + bio_end_sector(bio))
>> + wait = false;
>> + else if (conf->next_resync + NEXT_NORMALIO_DISTANCE
>> + <= bio->bi_sector) {
>> + if (conf->start_next_window == MaxSector)
>> + conf->start_next_window =
>> + conf->next_resync +
>> + NEXT_NORMALIO_DISTANCE;
>> +
>> + if ((conf->start_next_window + NEXT_NORMALIO_DISTANCE)
>> + <= bio->bi_sector)
>> + conf->next_window_requests++;
>> + else
>> + conf->current_window_requests++;
>> + } else
>> + wait = true;
>> + }
>> +
>> + return wait;
>> +}
>
>I really don't like it that this function changes start_next_window and
>*_window_requests().
>It looks like it is a simple function that tests a condition. But it
>actually has a side-effect as well. And it has the side-effect when it
>returns false which is extra confusing.
>
>Also, you are incrementing *_window_requests for READ requests, which you
>don't need to do.
>
For this, i think the patch had a error.
In func raise_barrier()
wait_event_lock_irq(conf->wait_barrier,
!conf->array_frozen &&
- !conf->nr_pending && conf->barrier < RESYNC_DEPTH,
+ !conf->nr_pending && conf->barrier < RESYNC_DEPTH &&
+ (conf->next_resync + RESYNC_SECTORS
+ <= conf->start_next_window),
Actualy, we should remove the conditon !conf->nr_pending. Resync don't need !conf->nr_pending.
And for read, i don't increase *_window_request.
[snip]
Below is my latest patch.
Subject:raid1: Rewrite the implementation of iobarrier.
>From c24142fa460596ccf461765dc77660edabd7e0a5 Mon Sep 17 00:00:00 2001
From: Jianpeng Ma <majianpeng@xxxxxxxxx>
Date: Mon, 28 Oct 2013 19:34:34 +0800
Subject: [PATCH] raid1: Rewrite the implementation of iobarrier
There is a iobarrier in raid1 because the contend between normal IO and
resync IO.It suspend all normal IO when reysync.
But if normalIO is outrange the resync windwos,there is no contend.
So I rewrite the iobarrier.
I patition the whole space into five parts.
|---------|-----------|------------|----------------|-------|
Pa next_resync start_next_window Pb
Pa + SYNC_WINDOW = next_resync
next_resync + NEXT_NORMALIO_DISTANCE = start_next_window
start_next_window + NEXT_NORMAILIO_DISTANCE = Pb
Firstly i introduce some concepts:
1:RESYNC_WINDOW: For resync, there are 32 resync requests at most at the
same time.A sync request is RESYNC_BLOCK_SIZE(64*1024).
So the RESYNC_WINDOW is 32 * RESYNC_BLOCK_SIZE, that is 2MB.
2:NEXT_NORMALIO_DISTANCE: it indicate the distance between next_resync
and start_next_window.It also indicate the distance between
start_next_window and Pb.Now it is 3 * RESYNC_WINDOW_SIZE.It can tune.
3:next_resync: mean the next start sector which will being do sync.
4:Pa means: a position which before RESYNC_WINDOW distance from
next_resync.
5:start_next_window: means a position which after NEXT_NORMALIO_DISTANCE
distance from next_resync.For normalio after this position,
it can't wait resyncio to complete.
6:Pb: means a position which after 2 * NEXT_NORMALIO_DISTANCE distance
from next_resync.
7:current_window_requests: means the count of normalIO between Pb and
start_next_window.
8:next_window_requests: means the count of nonmalIO after Pb.
NormalIO will be partitioned into four types:
NoIO1: it means the end sector of bio is smaller or equal the Pa.
NoIO2: it means the start sector of bio larger or equal Pb
NoIO3: it means the start sector of bio larger or equal
start_next_window.
NoIO4: it means the location between Pa and start_next_window
|--------|-----------|--------------------|----------------|---------|
| Pa | next_resync | start_next_window | Pb |
NoIO1 NoIO4 NoIO4 NoIO3 NoIO2
For NoIO1,it don't use iobarrier.
For NoIO4,it used the original iobarrier mechanism.The nornalIO and
resyncIO must be contend.
For NoIO2/3, i add two fields in struct r1conf "current_window_requests,
next_window_requests".They indicate the count of two types.
For those, they don't wait resync io to complete.
For resync action, if there are NoIO4s, it must be waited.If not,it
forward.But if sync action reached to the start_next_window and
current_window_requestes > 0 (that is there are NoIO3s),it must
wait until the current_window_requests became zero.
If current_window_requests became zero,the start_next_window also
forward. The current_window_requests will replaced by next_window_requests.
There is a problem which when and how to change from NoIO2 to NoIO3.Only
so, the sync action can forward.
I add a field in struct r1conf "start_next_window".What condition will
change?
A: if start_next_window == MaxSector, it means there are no NoIO2/3.
So start_next_window = next_resync + NEXT_NORMALIO_DISTANCE
B: if current_window_requests == 0 && next_window_requests != 0, it
means start_next_window move to Pb
There is anthor problem which how to differentiate between
old NoIO2(now it is NoIO3) and NoIO2.
For example, there are many bios which are NoIO2 and a bio which is
NoIO3. NoIO3 firstly completed,so the bios of NoIO2 became NoIO3.
At general,we use flags and list_head. The codes should:
>list_splice_init(NoIO2, NoIO3);
>current_window_requests = next_window_requests;
>next_window_requests = 0;
>list_for_each_entry(NoIO3){
> clear_bit(NoIO2_FLAG),
> set_bit(NoIO3_FLAG,
>}
If there are many NoIO2, it will take too much time in list_for_each_entry.
Avoid this, i add a field in struct r1bio "start_next_window".
I used this to record the position conf->start_next_window when call
wait_barrier in func make_request.
In func allow_barrier, it check the conf->start_next_window.
If r1bio->stat_next_window == conf->start_next_window,it mean
there is no transition between NoIO2 and NoIO3.
If r1bio->start_next_window != conf->start_next_window,it mean
there is a trnasiton between NoIO2 and NoIO3.Because there is at most one
transtion.So it only means the bio is old NoIO2.
For one bio,there are many r1bio's.So we make sure the
all r1bio->start_next_window are the same value.
If we met blocked_dev in make_request(), it must call allow_barrier
and wait_barrier.So the former and the later value of
conf->start_next_window will be change.
If there are many r1bio's with differnet start_next_window,
for the relevant bio, it depent on the last value of r1bio.
It will cause error.To avoid this, we must wait previous r1bios
to complete.
Signed-off-by: Jianpeng Ma <majianpeng@xxxxxxxxx>
---
drivers/md/raid1.c | 122 +++++++++++++++++++++++++++++++++++++++++++++++------
drivers/md/raid1.h | 14 ++++++
2 files changed, 124 insertions(+), 12 deletions(-)
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index b4a6dcd..5b311c0 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -66,7 +66,8 @@
*/
static int max_queued_requests = 1024;
-static void allow_barrier(struct r1conf *conf);
+static void allow_barrier(struct r1conf *conf, sector_t start_next_window,
+ sector_t bi_sector);
static void lower_barrier(struct r1conf *conf);
static void * r1bio_pool_alloc(gfp_t gfp_flags, void *data)
@@ -227,6 +228,8 @@ static void call_bio_endio(struct r1bio *r1_bio)
struct bio *bio = r1_bio->master_bio;
int done;
struct r1conf *conf = r1_bio->mddev->private;
+ sector_t start_next_window = r1_bio->start_next_window;
+ sector_t bi_sector = bio->bi_sector;
if (bio->bi_phys_segments) {
unsigned long flags;
@@ -234,6 +237,11 @@ static void call_bio_endio(struct r1bio *r1_bio)
bio->bi_phys_segments--;
done = (bio->bi_phys_segments == 0);
spin_unlock_irqrestore(&conf->device_lock, flags);
+ /*
+ * make_request() might be waiting for
+ * bi_phys_segments to decrease
+ */
+ wake_up(&conf->wait_barrier);
} else
done = 1;
@@ -245,7 +253,7 @@ static void call_bio_endio(struct r1bio *r1_bio)
* Wake up any possible resync thread that waits for the device
* to go idle.
*/
- allow_barrier(conf);
+ allow_barrier(conf, start_next_window, bi_sector);
}
}
@@ -827,10 +835,18 @@ static void raise_barrier(struct r1conf *conf)
/* block any new IO from starting */
conf->barrier++;
- /* Now wait for all pending IO to complete */
+ /* For those conditions we must wait:
+ * A:while the array is in frozen state
+ * B:while barrier >= RESYNC_DEPTH, meaning resync reach
+ * the max count which allowed.
+ * C:next_resync + RESYNC_SECTORS > start_next_window, meaning
+ * next resync will reach to window which normal bios are handling.
+ */
wait_event_lock_irq(conf->wait_barrier,
!conf->array_frozen &&
- !conf->nr_pending && conf->barrier < RESYNC_DEPTH,
+ conf->barrier < RESYNC_DEPTH &&
+ (conf->start_next_window >=
+ conf->next_resync + RESYNC_SECTORS),
conf->resync_lock);
spin_unlock_irq(&conf->resync_lock);
@@ -846,10 +862,33 @@ static void lower_barrier(struct r1conf *conf)
wake_up(&conf->wait_barrier);
}
-static void wait_barrier(struct r1conf *conf)
+static bool need_to_wait_for_sync(struct r1conf *conf, struct bio *bio)
+{
+ bool wait = false;
+
+ if (conf->array_frozen || !bio)
+ wait = true;
+ else if (conf->barrier && bio_data_dir(bio) == WRITE) {
+ if (conf->next_resync < RESYNC_WINDOW_SECTORS)
+ wait = true;
+ else if ((conf->next_resync - RESYNC_WINDOW_SECTORS
+ >= bio_end_sector(bio)) ||
+ (conf->next_resync + NEXT_NORMALIO_DISTANCE
+ <= bio->bi_sector))
+ wait = false;
+ else
+ wait = true;
+ }
+
+ return wait;
+}
+
+static sector_t wait_barrier(struct r1conf *conf, struct bio *bio)
{
+ sector_t sector = 0;
+
spin_lock_irq(&conf->resync_lock);
- if (conf->barrier) {
+ if (need_to_wait_for_sync(conf, bio)) {
conf->nr_waiting++;
/* Wait for the barrier to drop.
* However if there are already pending
@@ -868,16 +907,57 @@ static void wait_barrier(struct r1conf *conf)
!bio_list_empty(current->bio_list))),
conf->resync_lock);
conf->nr_waiting--;
+ } else if (bio_data_dir(bio) == WRITE) {
+ if (conf->next_resync + NEXT_NORMALIO_DISTANCE
+ <= bio->bi_sector) {
+ if (conf->start_next_window == MaxSector)
+ conf->start_next_window =
+ conf->next_resync +
+ NEXT_NORMALIO_DISTANCE;
+
+ if ((conf->start_next_window + NEXT_NORMALIO_DISTANCE)
+ <= bio->bi_sector)
+ conf->next_window_requests++;
+ else
+ conf->current_window_requests++;
+ }
+ if (bio->bi_sector >= conf->start_next_window)
+ sector = conf->start_next_window;
}
+
conf->nr_pending++;
spin_unlock_irq(&conf->resync_lock);
+ return sector;
}
-static void allow_barrier(struct r1conf *conf)
+static void allow_barrier(struct r1conf *conf, sector_t start_next_window,
+ sector_t bi_sector)
{
unsigned long flags;
+
spin_lock_irqsave(&conf->resync_lock, flags);
conf->nr_pending--;
+ if (start_next_window) {
+ if (start_next_window == conf->start_next_window) {
+ if (conf->start_next_window + NEXT_NORMALIO_DISTANCE
+ <= bi_sector)
+ conf->next_window_requests--;
+ else
+ conf->current_window_requests--;
+ } else
+ conf->current_window_requests--;
+
+ if (!conf->current_window_requests) {
+ if (conf->next_window_requests) {
+ conf->current_window_requests =
+ conf->next_window_requests;
+ conf->next_window_requests = 0;
+ conf->start_next_window +=
+ NEXT_NORMALIO_DISTANCE;
+ } else
+ conf->start_next_window = MaxSector;
+ }
+ }
spin_unlock_irqrestore(&conf->resync_lock, flags);
wake_up(&conf->wait_barrier);
}
@@ -1012,6 +1092,7 @@ static void make_request(struct mddev *mddev, struct bio * bio)
int first_clone;
int sectors_handled;
int max_sectors;
+ sector_t start_next_window;
/*
* Register the new request and wait if the reconstruction
@@ -1041,7 +1122,7 @@ static void make_request(struct mddev *mddev, struct bio * bio)
finish_wait(&conf->wait_barrier, &w);
}
- wait_barrier(conf);
+ start_next_window = wait_barrier(conf, bio);
bitmap = mddev->bitmap;
@@ -1162,6 +1243,7 @@ read_again:
disks = conf->raid_disks * 2;
retry_write:
+ r1_bio->start_next_window = start_next_window;
blocked_rdev = NULL;
rcu_read_lock();
max_sectors = r1_bio->sectors;
@@ -1230,14 +1312,24 @@ read_again:
if (unlikely(blocked_rdev)) {
/* Wait for this device to become unblocked */
int j;
+ sector_t old = start_next_window;
for (j = 0; j < i; j++)
if (r1_bio->bios[j])
rdev_dec_pending(conf->mirrors[j].rdev, mddev);
r1_bio->state = 0;
- allow_barrier(conf);
+ allow_barrier(conf, start_next_window, bio->bi_sector);
md_wait_for_blocked_rdev(blocked_rdev, mddev);
- wait_barrier(conf);
+ start_next_window = wait_barrier(conf, bio);
+ /*
+ * We must make sure the multi r1bios of bio have
+ * the same value of bi_phys_segments
+ */
+ if (bio->bi_phys_segments && old &&
+ old != start_next_window)
+ /*wait the former r1bio(s) completed*/
+ wait_event(conf->wait_barrier,
+ bio->bi_phys_segments == 1);
goto retry_write;
}
@@ -1437,11 +1529,14 @@ static void print_conf(struct r1conf *conf)
static void close_sync(struct r1conf *conf)
{
- wait_barrier(conf);
- allow_barrier(conf);
+ wait_barrier(conf, NULL);
+ allow_barrier(conf, 0, 0);
mempool_destroy(conf->r1buf_pool);
conf->r1buf_pool = NULL;
+
+ conf->next_resync = 0;
+ conf->start_next_window = MaxSector;
}
static int raid1_spare_active(struct mddev *mddev)
@@ -2713,6 +2808,9 @@ static struct r1conf *setup_conf(struct mddev *mddev)
conf->pending_count = 0;
conf->recovery_disabled = mddev->recovery_disabled - 1;
+ conf->start_next_window = MaxSector;
+ conf->current_window_requests = conf->next_window_requests = 0;
+
err = -EIO;
for (i = 0; i < conf->raid_disks * 2; i++) {
diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h
index 331a98a..07425a1 100644
--- a/drivers/md/raid1.h
+++ b/drivers/md/raid1.h
@@ -41,6 +41,19 @@ struct r1conf {
*/
sector_t next_resync;
+ /*when raid1 start resync,we divide raid into four partitions
+ * |---------|--------------|---------------------|-------------|
+ * next_resync start_next_window Pc
+ * Now start_next_window = next_resync + NEXT_NORMALIO_DISTANCE
+ * Pc = start_next_window + NEXT_NORMALIO_DISTANCE
+ * current_window_requests means the count of normalIO between
+ * start_next_window and Pc.
+ * next_window_requests means the count of nornalIO after Pc.
+ * */
+ sector_t start_next_window;
+ int current_window_requests;
+ int next_window_requests;
+
spinlock_t device_lock;
/* list of 'struct r1bio' that need to be processed by raid1d,
@@ -112,6 +125,7 @@ struct r1bio {
* in this BehindIO request
*/
sector_t sector;
+ sector_t start_next_window;
int sectors;
unsigned long state;
struct mddev *mddev;
--
1.8.4
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