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author | Coly Li <colyli@suse.de> | 2018-05-03 18:51:33 +0800 |
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committer | Jens Axboe <axboe@kernel.dk> | 2018-05-03 08:35:10 -0600 |
commit | 6147305c73e4511ca1a975b766b97a779d442567 (patch) | |
tree | a6daa1e3ae4e6a4f4a4cda990d6d380d249898b2 /drivers | |
parent | 6e916a7eb1bc045f4e27355632ee7692014e6e60 (diff) | |
download | linux-stable-6147305c73e4511ca1a975b766b97a779d442567.tar.gz linux-stable-6147305c73e4511ca1a975b766b97a779d442567.tar.bz2 linux-stable-6147305c73e4511ca1a975b766b97a779d442567.zip |
bcache: set CACHE_SET_IO_DISABLE in bch_cached_dev_error()
Commit c7b7bd07404c5 ("bcache: add io_disable to struct cached_dev") tries
to stop bcache device by calling bcache_device_stop() when too many I/O
errors happened on backing device. But if there is internal I/O happening
on cache device (writeback scan, garbage collection, etc), a regular I/O
request triggers the internal I/Os may still holds a refcount of dc->count,
and the refcount may only be dropped after the internal I/O stopped.
By this patch, bch_cached_dev_error() will check if the backing device is
attached to a cache set, if yes that CACHE_SET_IO_DISABLE will be set to
flags of this cache set. Then internal I/Os on cache device will be
rejected and stopped immediately, and the bcache device can be stopped.
For people who are not familiar with the interesting refcount dependance,
let me explain a bit more how the fix works. Example the writeback thread
will scan cache device for dirty data writeback purpose. Before it stopps,
it holds a refcount of dc->count. When CACHE_SET_IO_DISABLE bit is set,
the internal I/O will stopped and the while-loop in bch_writeback_thread()
quits and calls cached_dev_put() to drop dc->count. If this is the last
refcount to drop, then cached_dev_detach_finish() will be called. In this
call back function, in turn closure_put(dc->disk.cl) is called to drop a
refcount of closure dc->disk.cl. If this is the last refcount of this
closure to drop, then cached_dev_flush() will be called. Then the cached
device is freed. So if CACHE_SET_IO_DISABLE is not set, the bache device
can not be stopped until all inernal cache device I/O stopped. For large
size cache device, and writeback thread competes locks with gc thread,
there might be a quite long time to wait.
Fixes: c7b7bd07404c5 ("bcache: add io_disable to struct cached_dev")
Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/md/bcache/super.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 8196b19fada2..c017cd444c66 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -1369,6 +1369,8 @@ int bch_flash_dev_create(struct cache_set *c, uint64_t size) bool bch_cached_dev_error(struct cached_dev *dc) { + struct cache_set *c; + if (!dc || test_bit(BCACHE_DEV_CLOSING, &dc->disk.flags)) return false; @@ -1379,6 +1381,21 @@ bool bch_cached_dev_error(struct cached_dev *dc) pr_err("stop %s: too many IO errors on backing device %s\n", dc->disk.disk->disk_name, dc->backing_dev_name); + /* + * If the cached device is still attached to a cache set, + * even dc->io_disable is true and no more I/O requests + * accepted, cache device internal I/O (writeback scan or + * garbage collection) may still prevent bcache device from + * being stopped. So here CACHE_SET_IO_DISABLE should be + * set to c->flags too, to make the internal I/O to cache + * device rejected and stopped immediately. + * If c is NULL, that means the bcache device is not attached + * to any cache set, then no CACHE_SET_IO_DISABLE bit to set. + */ + c = dc->disk.c; + if (c && test_and_set_bit(CACHE_SET_IO_DISABLE, &c->flags)) + pr_info("CACHE_SET_IO_DISABLE already set"); + bcache_device_stop(&dc->disk); return true; } |