linux-kernel - [PATCH 3.16 108/133] bcache: initialize dirty stripes in flash_dev

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Message-ID: <lsq.1511315893.666712983@decadent.org.uk>
Date:   Wed, 22 Nov 2017 01:58:13 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Jens Axboe" <axboe@...nel.dk>,
        "Tang Junhui" <tang.junhui@....com.cn>, "Coly Li" <colyli@...e.de>
Subject: [PATCH 3.16 108/133] bcache: initialize dirty stripes in
 flash_dev_run()

3.16.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

commit 175206cf9ab63161dec74d9cd7f9992e062491f5 upstream.

bcache uses a Proportion-Differentiation Controller algorithm to control
writeback rate to cached devices. In the PD controller algorithm, dirty
stripes of thin flash device should not be counted in, because flash only
volumes never write back dirty data.

Currently dirty stripe counter for thin flash device is not initialized
when the thin flash device starts. Which means the following calculation
in PD controller will reference an undefined dirty stripes number, and
all cached devices attached to the same cache set where the thin flash
device lies on may have an inaccurate writeback rate.

This patch calles bch_sectors_dirty_init() in flash_dev_run(), to
correctly initialize dirty stripe counter when the thin flash device
starts to run. This patch also does following parameter data type change,
 -void bch_sectors_dirty_init(struct cached_dev *dc);
 +void bch_sectors_dirty_init(struct bcache_device *);
to call this function conveniently in flash_dev_run().

(Commit log is composed by Coly Li)

Signed-off-by: Tang Junhui <tang.junhui@....com.cn>
Reviewed-by: Coly Li <colyli@...e.de>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/md/bcache/super.c     | 3 ++-
 drivers/md/bcache/writeback.c | 8 ++++----
 drivers/md/bcache/writeback.h | 2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1045,7 +1045,7 @@ int bch_cached_dev_attach(struct cached_
 	atomic_set(&dc->count, 1);
 
 	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);
@@ -1248,6 +1248,7 @@ 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
+++ b/drivers/md/bcache/writeback.c
@@ -489,17 +489,17 @@ 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);
 }
 
 int bch_cached_dev_writeback_init(struct cached_dev *dc)
--- a/drivers/md/bcache/writeback.h
+++ b/drivers/md/bcache/writeback.h
@@ -104,7 +104,7 @@ 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 *);
 int bch_cached_dev_writeback_init(struct cached_dev *);
 
 #endif