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?
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)
--
2.18.4
