• Coly Li's avatar
    bcache: add CACHE_SET_IO_DISABLE to struct cache_set flags · 771f393e
    Coly Li authored
    When too many I/Os failed on cache device, bch_cache_set_error() is called
    in the error handling code path to retire whole problematic cache set. If
    new I/O requests continue to come and take refcount dc->count, the cache
    set won't be retired immediately, this is a problem.
    
    Further more, there are several kernel thread and self-armed kernel work
    may still running after bch_cache_set_error() is called. It needs to wait
    quite a while for them to stop, or they won't stop at all. They also
    prevent the cache set from being retired.
    
    The solution in this patch is, to add per cache set flag to disable I/O
    request on this cache and all attached backing devices. Then new coming I/O
    requests can be rejected in *_make_request() before taking refcount, kernel
    threads and self-armed kernel worker can stop very fast when flags bit
    CACHE_SET_IO_DISABLE is set.
    
    Because bcache also do internal I/Os for writeback, garbage collection,
    bucket allocation, journaling, this kind of I/O should be disabled after
    bch_cache_set_error() is called. So closure_bio_submit() is modified to
    check whether CACHE_SET_IO_DISABLE is set on cache_set->flags. If set,
    closure_bio_submit() will set bio->bi_status to BLK_STS_IOERR and
    return, generic_make_request() won't be called.
    
    A sysfs interface is also added to set or clear CACHE_SET_IO_DISABLE bit
    from cache_set->flags, to disable or enable cache set I/O for debugging. It
    is helpful to trigger more corner case issues for failed cache device.
    
    Changelog
    v4, add wait_for_kthread_stop(), and call it before exits writeback and gc
        kernel threads.
    v3, change CACHE_SET_IO_DISABLE from 4 to 3, since it is bit index.
        remove "bcache: " prefix when printing out kernel message.
    v2, more changes by previous review,
    - Use CACHE_SET_IO_DISABLE of cache_set->flags, suggested by Junhui.
    - Check CACHE_SET_IO_DISABLE in bch_btree_gc() to stop a while-loop, this
      is reported and inspired from origal patch of Pavel Vazharov.
    v1, initial version.
    Signed-off-by: default avatarColy Li <colyli@suse.de>
    Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
    Reviewed-by: default avatarMichael Lyle <mlyle@lyle.org>
    Cc: Junhui Tang <tang.junhui@zte.com.cn>
    Cc: Michael Lyle <mlyle@lyle.org>
    Cc: Pavel Vazharov <freakpv@gmail.com>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    771f393e
super.c 52.7 KB