Re: [PATCH v2] ataflop: remove ataflop_probe_lock mutex

Michael Schmitz
2021-10-18T08:15:43Z

Hi Tetsuo,

the ataflop driver got broken in commit 6ec3938cff95f (ataflop: convert
to blk-mq), three years ago. Can't remember seeing that one before.

Looking at a debug log, I get:

[ 7919.150000] fd_open: type=0
[ 7919.180000] Queue request: drive 0 type 0
[ 7919.200000] Request params: Si=0 Tr=0 Se=1 Data=00541000
[ 7919.200000] do_fd_action
[ 7919.200000] fd_rwsec(), Sec=1, Access=r
[ 7919.200000] finish_fdc: dummy seek started
[ 7920.550000] FDC irq, status = a0 handler = 001ea00a
[ 7920.550000] finish_fdc_done entered
[ 7920.550000] finish_fdc() finished

I would have expected an interrupt from fd_rwsec() (which sets
fd_rwsec_done() as IRQ handler), but calling finish_fdc() from the
request function while interrupts for the controller are disabled but a
request is in-flight pretty much ensures we never see fd_rwsec_done()
called:

ReqCnt = 0;
ReqCmd = rq_data_dir(fd_request);
ReqBlock = blk_rq_pos(fd_request);
ReqBuffer = bio_data(fd_request->bio);
setup_req_params( drive );
do_fd_action( drive );

if (bd->last)
finish_fdc();
atari_enable_irq( IRQ_MFP_FDC );

The old driver used a wait queue to serialize requests, and only called
finish_fdc() when no further requests were pending. I wonder how to make
sure finish_fdc() only gets called in the same situation now ...
bd->last clearly isn't the right hint here.

I suspect this isn't the only thing that broke...

Cheers,

Michael

On 18/10/21 12:47, Michael Schmitz wrote:
> Hi Tetsuo,
>
> nevermind - stock 5.9 doesn't work either (mount hangs indefinitely).
>
> Might have to do with format autoprobing - I'll try that next.
>
> Cheers,
>
> Michael
>
>
> On 18/10/21 08:05, Michael Schmitz wrote:
>>> Michael Schmitz wrote:
>>>> Not as a module, no. I use the Atari floppy driver built-in. Latest
>>>> kernel version I ran was 5.13.
>>>
>>> Great. Can you try this patch alone?
>>
>> Doesn't appear to work, sorry.
>>
>> Regards,
>>
>> Michael Schmitz
>>
>>>
>>> drivers/block/ataflop.c | 55 ++++++++++++++++++++---------------------
>>> 1 file changed, 27 insertions(+), 28 deletions(-)
>>>
>>> diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
>>> index a093644ac39f..adfe198e4699 100644
>>> --- a/drivers/block/ataflop.c
>>> +++ b/drivers/block/ataflop.c
>>> @@ -1986,8 +1986,6 @@ static int ataflop_alloc_disk(unsigned int
>>> drive, unsigned int type)
>>> return 0;
>>> }
>>>
>>> -static DEFINE_MUTEX(ataflop_probe_lock);
>>> -
>>> static void ataflop_probe(dev_t dev)
>>> {
>>> int drive = MINOR(dev) & 3;
>>> @@ -1998,12 +1996,30 @@ static void ataflop_probe(dev_t dev)
>>>
>>> if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS)
>>> return;
>>> - mutex_lock(&ataflop_probe_lock);
>>> if (!unit[drive].disk[type]) {
>>> if (ataflop_alloc_disk(drive, type) == 0)
>>> add_disk(unit[drive].disk[type]);
>>> }
>>> - mutex_unlock(&ataflop_probe_lock);
>>> +}
>>> +
>>> +static void atari_floppy_cleanup(void)
>>> +{
>>> + int i;
>>> + int type;
>>> +
>>> + for (i = 0; i < FD_MAX_UNITS; i++) {
>>> + for (type = 0; type < NUM_DISK_MINORS; type++) {
>>> + if (!unit[i].disk[type])
>>> + continue;
>>> + del_gendisk(unit[i].disk[type]);
>>> + blk_cleanup_queue(unit[i].disk[type]->queue);
>>> + put_disk(unit[i].disk[type]);
>>> + }
>>> + blk_mq_free_tag_set(&unit[i].tag_set);
>>> + }
>>> +
>>> + del_timer_sync(&fd_timer);
>>> + atari_stram_free(DMABuffer);
>>> }
>>>
>>> static int __init atari_floppy_init (void)
>>> @@ -2015,11 +2031,6 @@ static int __init atari_floppy_init (void)
>>> /* Amiga, Mac, ... don't have Atari-compatible floppy :-) */
>>> return -ENODEV;
>>>
>>> - mutex_lock(&ataflop_probe_lock);
>>> - ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);
>>> - if (ret)
>>> - goto out_unlock;
>>> -
>>> for (i = 0; i < FD_MAX_UNITS; i++) {
>>> memset(&unit[i].tag_set, 0, sizeof(unit[i].tag_set));
>>> unit[i].tag_set.ops = &ataflop_mq_ops;
>>> @@ -2072,7 +2083,12 @@ static int __init atari_floppy_init (void)
>>> UseTrackbuffer ? "" : "no ");
>>> config_types();
>>>
>>> - return 0;
>>> + ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);
>>> + if (ret) {
>>> + printk(KERN_ERR "atari_floppy_init: cannot register block
>>> device\n");
>>> + atari_floppy_cleanup();
>>> + }
>>> + return ret;
>>>
>>> err:
>>> while (--i >= 0) {
>>> @@ -2081,9 +2097,6 @@ static int __init atari_floppy_init (void)
>>> blk_mq_free_tag_set(&unit[i].tag_set);
>>> }
>>>
>>> - unregister_blkdev(FLOPPY_MAJOR, "fd");
>>> -out_unlock:
>>> - mutex_unlock(&ataflop_probe_lock);
>>> return ret;
>>> }
>>>
>>> @@ -2128,22 +2141,8 @@ __setup("floppy=", atari_floppy_setup);
>>>
>>> static void __exit atari_floppy_exit(void)
>>> {
>>> - int i, type;
>>> -
>>> - for (i = 0; i < FD_MAX_UNITS; i++) {
>>> - for (type = 0; type < NUM_DISK_MINORS; type++) {
>>> - if (!unit[i].disk[type])
>>> - continue;
>>> - del_gendisk(unit[i].disk[type]);
>>> - blk_cleanup_queue(unit[i].disk[type]->queue);
>>> - put_disk(unit[i].disk[type]);
>>> - }
>>> - blk_mq_free_tag_set(&unit[i].tag_set);
>>> - }
>>> unregister_blkdev(FLOPPY_MAJOR, "fd");
>>> -
>>> - del_timer_sync(&fd_timer);
>>> - atari_stram_free( DMABuffer );
>>> + atari_floppy_cleanup();
>>> }
>>>
>>> module_init(atari_floppy_init)
>>>