On 04/01/2018 1:59 AM, tang.junhui@zte.com.cn wrote:

From: Tang Junhui <redacted>

Hello Coly,

This patch is great!

One tips,
Could you replace the c->io_disable with the already exsited c->flags? 
So we can just need to add a new macro such as CACHE_SET_IO_DISABLE.

Hi Junhui,

Your suggestion is cool! I will do it in v2 set. Thanks.

Coly Li

quoted

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 io_disable is
true.

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 true. If cache_set->io_disable is
true, 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 for cache_set->io_disable, to read and set
io_disable value for debugging. It is helpful to trigger more corner case
issues for failed cache device.

Signed-off-by: Coly Li <redacted>

[snip]