On 5/26/20 3:49 AM, Jiri Kosina wrote: > From: Jiri Kosina <jkosina@xxxxxxx> > > Since the switch of floppy driver to blk-mq, the contended (fdc_busy) case > in floppy_queue_rq() is not handled correctly. > > In case we reach floppy_queue_rq() with fdc_busy set (i.e. with the floppy > locked due to another request still being in-flight), we put the request > on the list of requests and return BLK_STS_OK to the block core, without > actually scheduling delayed work / doing further processing of the > request. This means that processing of this request is postponed until > another request comes and passess uncontended. > > Which in some cases might actually never happen and we keep waiting > indefinitely. The simple testcase is > > for i in `seq 1 2000`; do echo -en $i '\r'; blkid --info /dev/fd0 2> /dev/null; done > > run in quemu. That reliably causes blkid eventually indefinitely hanging > in __floppy_read_block_0() waiting for completion, as the BIO callback > never happens, and no further IO is ever submitted on the (non-existent) > floppy device. This was observed reliably on qemu-emulated device. > > Fix that by not queuing the request in the contended case, and return > BLK_STS_RESOURCE instead, so that blk core handles the request > rescheduling and let it pass properly non-contended later. Applied, thanks. -- Jens Axboe
