Hi Tetsu,
On 17/10/21 15:09, Tetsuo Handa wrote:
Commit bf9c0538e485b591 ("ataflop: use a separate gendisk for each media
format") introduced ataflop_probe_lock mutex, but forgot to unlock the
mutex when atari_floppy_init() (i.e. module loading) succeeded. This will
result in double lock deadlock if ataflop_probe() is called. Also,
unregister_blkdev() must not be called from atari_floppy_init() with
ataflop_probe_lock held when atari_floppy_init() failed, for
ataflop_probe() waits for ataflop_probe_lock with major_names_lock held
(i.e. AB-BA deadlock).
__register_blkdev() needs to be called last in order to avoid calling
ataflop_probe() when atari_floppy_init() is about to fail, for memory for
completing already-started ataflop_probe() safely will be released as soon
as atari_floppy_init() released ataflop_probe_lock mutex.
As with commit 8b52d8be86d72308 ("loop: reorder loop_exit"),
unregister_blkdev() needs to be called first in order to avoid calling
ataflop_alloc_disk() from ataflop_probe() after del_gendisk() from
atari_floppy_exit().
By relocating __register_blkdev() / unregister_blkdev() as explained above,
we can remove ataflop_probe_lock mutex, for probe function and __exit
function are serialized by major_names_lock mutex.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Fixes: bf9c0538e485b591 ("ataflop: use a separate gendisk for each media format")
---
Changes in v2:
Remove ataflop_probe_lock mutex than unlocking.
Finn Thain wrote:
So I wonder if it would have been possible to use Aranym to find the
regression, or avoid it in the first place?
OK, there is an emulator for testing this module. But I'm not familiar
with m68k environment. Luis Chamberlain is proposing patchset for adding
add_disk() error handling. I think that an answer would be to include
m68k's mailing list into a patch for this module in order to notify of
changes and expect m68k developers to review/test the patch.
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?
Works, after fixing the ataflop_queue_rq() breakage (separate patch sent).
Tested-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
Thanks,
Michael
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)
