2021-10-15 18:33:59

by Lin Feng

Subject: [PATCH] bcache: move calc_cached_dev_sectors to proper place on backing device detach

Calculation of cache_set's cached sectors is done by travelling
cached_devs list as shown below:

static void calc_cached_dev_sectors(struct cache_set *c)
{
...
list_for_each_entry(dc, &c->cached_devs, list)
sectors += bdev_sectors(dc->bdev);

c->cached_dev_sectors = sectors;
}

But cached_dev won't be unlinked from c->cached_devs list until we call
following list_move(&dc->list, &uncached_devices),
so previous fix in 'commit 46010141da6677b81cc77f9b47f8ac62bd1cbfd3
("bcache: recal cached_dev_sectors on detach")' is wrong, now we move
it to its right palce.

Signed-off-by: Lin Feng <[email protected]>
---
drivers/md/bcache/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index f2874c77ff79..8543e6997770 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1154,9 +1154,9 @@ static void cached_dev_detach_finish(struct work_struct *w)

mutex_lock(&bch_register_lock);

- calc_cached_dev_sectors(dc->disk.c);
bcache_device_detach(&dc->disk);
list_move(&dc->list, &uncached_devices);
+ calc_cached_dev_sectors(dc->disk.c);

clear_bit(BCACHE_DEV_DETACHING, &dc->disk.flags);
clear_bit(BCACHE_DEV_UNLINK_DONE, &dc->disk.flags);
--
2.31.1

2021-10-18 14:41:17

by Coly Li

Subject: Re: [PATCH] bcache: move calc_cached_dev_sectors to proper place on backing device detach

On 10/15/21 6:16 PM, Lin Feng wrote:
> Calculation of cache_set's cached sectors is done by travelling
> cached_devs list as shown below:
>
> static void calc_cached_dev_sectors(struct cache_set *c)
> {
> ...
> list_for_each_entry(dc, &c->cached_devs, list)
> sectors += bdev_sectors(dc->bdev);
>
> c->cached_dev_sectors = sectors;
> }
>
> But cached_dev won't be unlinked from c->cached_devs list until we call
> following list_move(&dc->list, &uncached_devices),
> so previous fix in 'commit 46010141da6677b81cc77f9b47f8ac62bd1cbfd3
> ("bcache: recal cached_dev_sectors on detach")' is wrong, now we move
> it to its right palce.
>
> Signed-off-by: Lin Feng <[email protected]>

Nice catch! I added it in my testing series. Thanks.

Coly Li

> ---
> drivers/md/bcache/super.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index f2874c77ff79..8543e6997770 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -1154,9 +1154,9 @@ static void cached_dev_detach_finish(struct work_struct *w)
>
> mutex_lock(&bch_register_lock);
>
> - calc_cached_dev_sectors(dc->disk.c);
> bcache_device_detach(&dc->disk);
> list_move(&dc->list, &uncached_devices);
> + calc_cached_dev_sectors(dc->disk.c);
>
> clear_bit(BCACHE_DEV_DETACHING, &dc->disk.flags);
> clear_bit(BCACHE_DEV_UNLINK_DONE, &dc->disk.flags);