[PATCH 4.14 149/183] bcache: fix for data collapse after re-attaching an attached device

From: Greg Kroah-Hartman
Date: Wed Apr 25 2018 - 06:45:19 EST

4.14-stable review patch. If anyone has any objections, please let me know.


From: Tang Junhui <tang.junhui@xxxxxxxxxx>

[ Upstream commit 73ac105be390c1de42a2f21643c9778a5e002930 ]

back-end device sdm has already attached a cache_set with ID
f67ebe1f-f8bc-4d73-bfe5-9dc88607f119, then try to attach with
another cache set, and it returns with an error:
[root]# cd /sys/block/sdm/bcache
[root]# echo 5ccd0a63-148e-48b8-afa2-aca9cbd6279f > attach
-bash: echo: write error: Invalid argument

After that, execute a command to modify the label of bcache
[root]# echo data_disk1 > label

Then we reboot the system, when the system power on, the back-end
device can not attach to cache_set, a messages show in the log:
Feb 5 12:05:52 ceph152 kernel: [922385.508498] bcache:
bch_cached_dev_attach() couldn't find uuid for sdm in set

In sysfs_attach(), dc->sb.set_uuid was assigned to the value
which input through sysfs, no matter whether it is success
or not in bch_cached_dev_attach(). For example, If the back-end
device has already attached to an cache set, bch_cached_dev_attach()
would fail, but dc->sb.set_uuid was changed. Then modify the
label of bcache device, it will call bch_write_bdev_super(),
which would write the dc->sb.set_uuid to the super block, so we
record a wrong cache set ID in the super block, after the system
reboot, the cache set couldn't find the uuid of the back-end
device, so the bcache device couldn't exist and use any more.

In this patch, we don't assigned cache set ID to dc->sb.set_uuid
in sysfs_attach() directly, but input it into bch_cached_dev_attach(),
and assigned dc->sb.set_uuid to the cache set ID after the back-end
device attached to the cache set successful.

Signed-off-by: Tang Junhui <tang.junhui@xxxxxxxxxx>
Reviewed-by: Michael Lyle <mlyle@xxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
drivers/md/bcache/bcache.h | 2 +-
drivers/md/bcache/super.c | 10 ++++++----
drivers/md/bcache/sysfs.c | 6 ++++--
3 files changed, 11 insertions(+), 7 deletions(-)

--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -906,7 +906,7 @@ void bcache_write_super(struct cache_set

int bch_flash_dev_create(struct cache_set *c, uint64_t size);

-int bch_cached_dev_attach(struct cached_dev *, struct cache_set *);
+int bch_cached_dev_attach(struct cached_dev *, struct cache_set *, uint8_t *);
void bch_cached_dev_detach(struct cached_dev *);
void bch_cached_dev_run(struct cached_dev *);
void bcache_device_stop(struct bcache_device *);
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -939,7 +939,8 @@ void bch_cached_dev_detach(struct cached

-int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c)
+int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
+ uint8_t *set_uuid)
uint32_t rtime = cpu_to_le32(get_seconds());
struct uuid_entry *u;
@@ -948,7 +949,8 @@ int bch_cached_dev_attach(struct cached_

bdevname(dc->bdev, buf);

- if (memcmp(dc->sb.set_uuid, c->sb.set_uuid, 16))
+ if ((set_uuid && memcmp(set_uuid, c->sb.set_uuid, 16)) ||
+ (!set_uuid && memcmp(dc->sb.set_uuid, c->sb.set_uuid, 16)))
return -ENOENT;

if (dc->disk.c) {
@@ -1190,7 +1192,7 @@ static void register_bdev(struct cache_s

list_add(&dc->list, &uncached_devices);
list_for_each_entry(c, &bch_cache_sets, list)
- bch_cached_dev_attach(dc, c);
+ bch_cached_dev_attach(dc, c, NULL);

if (BDEV_STATE(&dc->sb) == BDEV_STATE_NONE ||
@@ -1712,7 +1714,7 @@ static void run_cache_set(struct cache_s

list_for_each_entry_safe(dc, t, &uncached_devices, list)
- bch_cached_dev_attach(dc, c);
+ bch_cached_dev_attach(dc, c, NULL);


--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -265,11 +265,13 @@ STORE(__cached_dev)

if (attr == &sysfs_attach) {
- if (bch_parse_uuid(buf, dc->sb.set_uuid) < 16)
+ uint8_t set_uuid[16];
+ if (bch_parse_uuid(buf, set_uuid) < 16)
return -EINVAL;

list_for_each_entry(c, &bch_cache_sets, list) {
- v = bch_cached_dev_attach(dc, c);
+ v = bch_cached_dev_attach(dc, c, set_uuid);
if (!v)
return size;