Re: [PULL] bcache updates based on git.kernel.dk/linux-block:for-next

Eddie Chapman
2017-07-18T18:31:37Z

As per previous mail, below are the 4 patches discussed, generated with
diff -up, from kernel.org 4.4.77, so with correct context for 4.4. Just
in case they are useful for anyone.

---
From: Tang Junhui <tang.junhui@zte.com.cn>

Sequential write IOs were tested with bs=1M by FIO in writeback cache
mode, these IOs were expected to be bypassed, but actually they did not.
We debug the code, and find in check_should_bypass():
if (!congested &&
mode == CACHE_MODE_WRITEBACK &&
op_is_write(bio_op(bio)) &&
(bio-＞bi_opf & REQ_SYNC))
goto rescale
that means, If in writeback mode, a write IO with REQ_SYNC flag will not
be bypassed though it is a sequential large IO, It's not a correct thing
to do actually, so this patch remove these codes.

Signed-off-by: tang.junhui <tang.junhui@zte.com.cn>
Reviewed-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Eric Wheeler <bcache@linux.ewheeler.net>
Cc: stable@vger.kernel.org
---

--- a/drivers/md/bcache/request.c 2017-07-18 18:09:38.686156583 +0100
+++ b/drivers/md/bcache/request.c 2017-07-18 18:09:44.596167542 +0100
@@ -400,12 +400,6 @@ static bool check_should_bypass(struct c
if (!congested && !dc->sequential_cutoff)
goto rescale;

- if (!congested &&
- mode == CACHE_MODE_WRITEBACK &&
- (bio->bi_rw & REQ_WRITE) &&
- (bio->bi_rw & REQ_SYNC))
- goto rescale;
-
spin_lock(&dc->io_lock);

hlist_for_each_entry(i, iohash(dc, bio->bi_iter.bi_sector), hash)

From: Tang Junhui <tang.junhui@zte.com.cn>

Since bypassed IOs use no bucket, so do not subtract sectors_to_gc to
trigger gc thread.

Signed-off-by: tang.junhui <tang.junhui@zte.com.cn>
Reviewed-by: Eric Wheeler <bcache@linux.ewheeler.net>
Cc: stable@vger.kernel.org
---

--- a/drivers/md/bcache/request.c 2017-07-18 18:18:43.937169337 +0100
+++ b/drivers/md/bcache/request.c 2017-07-18 18:21:45.637507148 +0100
@@ -196,12 +196,12 @@ static void bch_data_insert_start(struct
struct data_insert_op *op = container_of(cl, struct data_insert_op, cl);
struct bio *bio = op->bio, *n;

- if (atomic_sub_return(bio_sectors(bio), &op->c->sectors_to_gc) < 0)
- wake_up_gc(op->c);
-
if (op->bypass)
return bch_data_invalidate(cl);

+ if (atomic_sub_return(bio_sectors(bio), &op->c->sectors_to_gc) < 0)
+ wake_up_gc(op->c);
+
/*
* Journal writes are marked REQ_FLUSH; if the original write was a
* flush, it'll wait on the journal write.

From: Tang Junhui <tang.junhui@zte.com.cn>

Thin flash device does not initialize stripe_sectors_dirty correctly, this
patch fixes this issue.

Signed-off-by: Tang Junhui <tang.junhui@zte.com.cn>
Cc: stable@vger.kernel.org
---

--- a/drivers/md/bcache/super.c 2017-07-18 18:31:38.968611871 +0100
+++ b/drivers/md/bcache/super.c 2017-07-18 18:32:36.078718382 +0100
@@ -1023,7 +1023,7 @@ int bch_cached_dev_attach(struct cached_
}

if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {
- bch_sectors_dirty_init(dc);
+ bch_sectors_dirty_init(&dc->disk);
atomic_set(&dc->has_dirty, 1);
atomic_inc(&dc->count);
bch_writeback_queue(dc);
@@ -1227,6 +1227,7 @@ static int flash_dev_run(struct cache_se
goto err;

bcache_device_attach(d, c, u - c->uuids);
+ bch_sectors_dirty_init(d);
bch_flash_dev_request_init(d);
add_disk(d->disk);

--- a/drivers/md/bcache/writeback.c 2017-07-18 18:31:50.718633782 +0100
+++ b/drivers/md/bcache/writeback.c 2017-07-18 18:32:36.078718382 +0100
@@ -488,17 +488,17 @@ static int sectors_dirty_init_fn(struct
return MAP_CONTINUE;
}

-void bch_sectors_dirty_init(struct cached_dev *dc)
+void bch_sectors_dirty_init(struct bcache_device *d)
{
struct sectors_dirty_init op;

bch_btree_op_init(&op.op, -1);
- op.inode = dc->disk.id;
+ op.inode = d->id;

- bch_btree_map_keys(&op.op, dc->disk.c, &KEY(op.inode, 0, 0),
+ bch_btree_map_keys(&op.op, d->c, &KEY(op.inode, 0, 0),
sectors_dirty_init_fn, 0);

- dc->disk.sectors_dirty_last = bcache_dev_sectors_dirty(&dc->disk);
+ d->sectors_dirty_last = bcache_dev_sectors_dirty(d);
}

void bch_cached_dev_writeback_init(struct cached_dev *dc)
--- a/drivers/md/bcache/writeback.h 2017-07-18 18:32:00.588652189 +0100
+++ b/drivers/md/bcache/writeback.h 2017-07-18 18:32:36.078718382 +0100
@@ -85,7 +85,7 @@ static inline void bch_writeback_add(str

void bcache_dev_sectors_dirty_add(struct cache_set *, unsigned, uint64_t, int);

-void bch_sectors_dirty_init(struct cached_dev *dc);
+void bch_sectors_dirty_init(struct bcache_device *);
void bch_cached_dev_writeback_init(struct cached_dev *);
int bch_cached_dev_writeback_start(struct cached_dev *);

From: Tang Junhui <tang.junhui@zte.com.cn>

Since dirty sectors of thin flash cannot be used to cache data for backend
device, so we should subtract it in calculating writeback rate.

Signed-off-by: Tang Junhui <tang.junhui@zte.com.cn>
Cc: stable@vger.kernel.org
---

--- a/drivers/md/bcache/writeback.c 2017-07-18 18:38:46.929410077 +0100
+++ b/drivers/md/bcache/writeback.c 2017-07-18 18:39:00.979436233 +0100
@@ -21,7 +21,7 @@
static void __update_writeback_rate(struct cached_dev *dc)
{
struct cache_set *c = dc->disk.c;
- uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size;
+ uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size - bcache_flash_devs_sectors_dirty(c);
uint64_t cache_dirty_target =
div_u64(cache_sectors * dc->writeback_percent, 100);

--- a/drivers/md/bcache/writeback.h 2017-07-18 18:38:50.489416705 +0100
+++ b/drivers/md/bcache/writeback.h 2017-07-18 18:39:00.979436233 +0100
@@ -14,6 +14,25 @@ static inline uint64_t bcache_dev_sector
return ret;
}

+static inline uint64_t bcache_flash_devs_sectors_dirty(struct cache_set *c)
+{
+ uint64_t i, ret = 0;
+
+ mutex_lock(&bch_register_lock);
+
+ for (i = 0; i < c->nr_uuids; i++) {
+ struct bcache_device *d = c->devices[i];
+
+ if (!d || !UUID_FLASH_ONLY(&c->uuids[i]))
+ continue;
+ ret += bcache_dev_sectors_dirty(d);
+ }
+
+ mutex_unlock(&bch_register_lock);
+
+ return ret;
+}
+
static inline unsigned offset_to_stripe(struct bcache_device *d,
uint64_t offset)
{