There was a possibility for infinite do-while loop inside the GC thread
function in case of total failure of the caching device. I was able to
reproduce it 3 times simulating disappearing of the caching device via
'echo 1 > /sys/block/<dev>/device/delete'. In that case the btree_root
starts to return non zero and non -EAGAIN result, 'gc failed' message
start to fill the kernel log and the do-while becomes infinite loop
occupying single CPU core at 100%.
There is already a logic which unregisters the cache_set (or panics) in
case of io errors and thus we exit the loop here if the unregistering
procedure has already started.
Signed-off-by: Pavel Vazharov <freakpv@xxxxxxxxx>
---
drivers/md/bcache/btree.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 81e8dc3..a672081 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1748,8 +1748,12 @@ static void bch_btree_gc(struct cache_set *c)
closure_sync(&writes);
cond_resched();
- if (ret && ret != -EAGAIN)
- pr_warn("gc failed!");
+ if (ret && ret != -EAGAIN) {
+ if (test_bit(CACHE_SET_UNREGISTERING, &c->flags))
+ break;
+ else
+ pr_warn("gc failed!");
+ }
} while (ret);
bch_btree_gc_finish(c);
--
2.7.4
--
To unsubscribe from this list: send the line "unsubscribe linux-bcache" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
