During the testing we found the sync read bio can go through
path:
md_do_sync()
sync_request()
generic_make_request()
blk_queue_bio()
blk_attempt_plug_merge()
bio->bi_next CHAINED HERE
...
raid1d()
sync_request_write()
fix_sync_read_error()
if FailFast && Faulty
bio->bi_end_io = end_sync_write
generic_make_request()
BUG_ON(bio->bi_next)
This need to meet the conditions:
* bio once merged
* read disk have FailFast enabled
* read disk is Faulty
And since the block layer won't reset the 'bi_next' after bio
is done inside request, we hit the BUG like that.
This patch simply reset the bi_next before we reuse it.
Signed-off-by: Michael Wang <yun.wang@xxxxxxxxxxxxxxxx>
---
drivers/md/raid1.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 7d67235..0554110 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1986,11 +1986,13 @@ static int fix_sync_read_error(struct r1bio *r1_bio)
/* Don't try recovering from here - just fail it
* ... unless it is the last working device of course */
md_error(mddev, rdev);
- if (test_bit(Faulty, &rdev->flags))
+ if (test_bit(Faulty, &rdev->flags)) {
/* Don't try to read from here, but make sure
* put_buf does it's thing
*/
bio->bi_end_io = end_sync_write;
+ bio->bi_next = NULL;
+ }
}
while(sectors) {
--
2.5.0
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