[PATCH v4 00/13] bcache: device failure handling improvement

Coly Li
2018-01-28T11:08:42Z

Hi maintainers and folks,

This patch set tries to improve bcache device failure handling, includes
cache device and backing device failures.

The basic idea to handle failed cache device is,
- Unregister cache set
- Detach all backing devices which are attached to this cache set
- Stop all the detached bcache devices (configurable)
- Stop all flash only volume on the cache set
The above process is named 'cache set retire' by me. The result of cache
set retire is, cache set and bcache devices are all removed, following
I/O requests will get failed immediately to notift upper layer or user
space coce that the cache device is failed or disconnected.

For failed backing device, there are two kinds of failures to handle,
- If device is disconnected, and kernel thread dc->status_update_thread
finds it is offline for BACKING_DEV_OFFLINE_TIMEOUT (5) seconds, the
kernel thread will set dc->io_disable and call bcache_device_stop() to
stop and remove the bcache device from system.
- If device is alive but returns too many I/O errors, after errors number
exceeds dc->error_limit, call bch_cached_dev_error() to set
dc->io_disable and stop bcache device. Then the broken backing device
and its bcache device will be removed from system.

The v4 patch set combines two v3 patches into one, and adds one more patch
to permit users to explicitly avoid stopping attached bcache device from a
retiring cache set. This is a configurable option suggested by
Nix <nix@esperi.org.uk>.

Some patches of this patch set is already in bcache-for-next and not
included here anymore. Most of the patches are reviewed by Hannes Reinecke
and Junhui Tang. There are still severl patches need to be reviewed,
- [PATCH v4 05/13] bcache: stop dc->writeback_rate_update properly
- [PATCH v4 13/13] bcache: add stop_attached_devs_on_fail to struct
cached_dev

Any comment, question and review are warmly welcome. Thanks in advance.

Changelog:
v4: add per-cached_dev option stop_attached_devs_on_fail to avoid stopping
attached bcache device from a retiring cache set.
v3: fix detach issue find in v2 patch set.
v2: fixes all problems found in v1 review.
add patches to handle backing device failure.
add one more patch to set writeback_rate_update_seconds range.
include a patch from Junhui Tang.
v1: the initial version, only handles cache device failure.

Coly Li
---

Coly Li (12):
bcache: set writeback_rate_update_seconds in range [1, 60] seconds
bcache: properly set task state in bch_writeback_thread()
bcache: fix cached_dev->count usage for bch_cache_set_error()
bcache: quit dc->writeback_thread when BCACHE_DEV_DETACHING is set
bcache: stop dc->writeback_rate_update properly
bcache: set error_limit correctly
bcache: add CACHE_SET_IO_DISABLE to struct cache_set flags
bcache: stop all attached bcache devices for a retired cache set
bcache: add backing_request_endio() for bi_end_io of attached backing
device I/O
bcache: add io_disable to struct cached_dev
bcache: stop bcache device when backing device is offline
bcache: add stop_attached_devs_on_fail to struct cached_dev

Tang Junhui (1):
bcache: fix inaccurate io state for detached bcache devices

drivers/md/bcache/alloc.c | 5 +-
drivers/md/bcache/bcache.h | 38 ++++++++-
drivers/md/bcache/btree.c | 10 ++-
drivers/md/bcache/io.c | 16 +++-
drivers/md/bcache/journal.c | 4 +-
drivers/md/bcache/request.c | 187 +++++++++++++++++++++++++++++++++++-------
drivers/md/bcache/super.c | 181 ++++++++++++++++++++++++++++++++++++----
drivers/md/bcache/sysfs.c | 55 ++++++++++++-
drivers/md/bcache/util.h | 6 --
drivers/md/bcache/writeback.c | 99 ++++++++++++++++++----
drivers/md/bcache/writeback.h | 5 +-
11 files changed, 522 insertions(+), 84 deletions(-)

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2.15.1