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ataflop: remove ataflop_probe_lock mutex

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Commit bf9c0538e4 ("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 8b52d8be86 ("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@I-love.SAKURA.ne.jp>
Fixes: bf9c0538e4 ("ataflop: use a separate gendisk for each media format")
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Link: https://lore.kernel.org/r/20211103230437.1639990-11-mcgrof@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tetsuo Handa 2021-11-03 16:04:33 -07:00 committed by Jens Axboe
parent ed73919124
commit 4ddb85d366
1 changed files with 27 additions and 20 deletions
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47
drivers/block/ataflop.c
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@ -2008,8 +2008,6 @@ static int ataflop_alloc_disk(unsigned int drive, unsigned int type)
return 0; return 0;
} }
static DEFINE_MUTEX(ataflop_probe_lock);
static void ataflop_probe(dev_t dev) static void ataflop_probe(dev_t dev)
{ {
int drive = MINOR(dev) & 3; int drive = MINOR(dev) & 3;
@ -2020,14 +2018,32 @@ static void ataflop_probe(dev_t dev)
if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS) if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS)
return; return;
mutex_lock(&ataflop_probe_lock);
if (!unit[drive].disk[type]) { if (!unit[drive].disk[type]) {
if (ataflop_alloc_disk(drive, type) == 0) { if (ataflop_alloc_disk(drive, type) == 0) {
add_disk(unit[drive].disk[type]); add_disk(unit[drive].disk[type]);
unit[drive].registered[type] = true; unit[drive].registered[type] = true;
} }
} }
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 void atari_cleanup_floppy_disk(struct atari_floppy_struct *fs) static void atari_cleanup_floppy_disk(struct atari_floppy_struct *fs)
@ -2053,11 +2069,6 @@ static int __init atari_floppy_init (void)
/* Amiga, Mac, ... don't have Atari-compatible floppy :-) */ /* Amiga, Mac, ... don't have Atari-compatible floppy :-) */
return -ENODEV; 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++) { for (i = 0; i < FD_MAX_UNITS; i++) {
memset(&unit[i].tag_set, 0, sizeof(unit[i].tag_set)); memset(&unit[i].tag_set, 0, sizeof(unit[i].tag_set));
unit[i].tag_set.ops = &ataflop_mq_ops; unit[i].tag_set.ops = &ataflop_mq_ops;
@ -2113,7 +2124,12 @@ static int __init atari_floppy_init (void)
UseTrackbuffer ? "" : "no "); UseTrackbuffer ? "" : "no ");
config_types(); 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_out_dma: err_out_dma:
atari_stram_free(DMABuffer); atari_stram_free(DMABuffer);
@ -2121,9 +2137,6 @@ err:
while (--i >= 0) while (--i >= 0)
atari_cleanup_floppy_disk(&unit[i]); atari_cleanup_floppy_disk(&unit[i]);
unregister_blkdev(FLOPPY_MAJOR, "fd");
out_unlock:
mutex_unlock(&ataflop_probe_lock);
return ret; return ret;
} }
@ -2168,14 +2181,8 @@ __setup("floppy=", atari_floppy_setup);
static void __exit atari_floppy_exit(void) static void __exit atari_floppy_exit(void)
{ {
int i;
for (i = 0; i < FD_MAX_UNITS; i++)
atari_cleanup_floppy_disk(&unit[i]);
unregister_blkdev(FLOPPY_MAJOR, "fd"); unregister_blkdev(FLOPPY_MAJOR, "fd");
atari_floppy_cleanup();
del_timer_sync(&fd_timer);
atari_stram_free( DMABuffer );
} }
module_init(atari_floppy_init) module_init(atari_floppy_init)