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    Subject[PATCH AUTOSEL for 4.9 283/293] bcache: fix for data collapse after re-attaching an attached device
    Date
    From: Tang Junhui <tang.junhui@zte.com.cn>

    [ 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
    device:
    [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@zte.com.cn>
    Reviewed-by: Michael Lyle <mlyle@lyle.org>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    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(-)

    diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
    index 02619cabda8b..7fe7df56fa33 100644
    --- a/drivers/md/bcache/bcache.h
    +++ b/drivers/md/bcache/bcache.h
    @@ -904,7 +904,7 @@ 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 *);
    diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
    index 1a006f989ac2..757b13deeb1c 100644
    --- a/drivers/md/bcache/super.c
    +++ b/drivers/md/bcache/super.c
    @@ -932,7 +932,8 @@ void bch_cached_dev_detach(struct cached_dev *dc)
    cached_dev_put(dc);
    }

    -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;
    @@ -941,7 +942,8 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c)

    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) {
    @@ -1185,7 +1187,7 @@ static void register_bdev(struct cache_sb *sb, struct page *sb_page,

    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 ||
    BDEV_STATE(&dc->sb) == BDEV_STATE_STALE)
    @@ -1708,7 +1710,7 @@ static void run_cache_set(struct cache_set *c)
    bcache_write_super(c);

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

    flash_devs_run(c);

    diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
    index 4fbb5532f24c..1efe31615281 100644
    --- a/drivers/md/bcache/sysfs.c
    +++ b/drivers/md/bcache/sysfs.c
    @@ -263,11 +263,13 @@ 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;
    }
    --
    2.15.1
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