ataflop: remove ataflop_probe_lock mutex

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@I-love.SAKURA.ne.jp>
Fixes: bf9c0538e485b591 ("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>

diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
index d14bdc3589b23501848afd9e769ce16a3c93baef..170dd193cef6d835c59241472e504fd04058dc3a 100644 (file)
--- a/drivers/block/ataflop.c
+++ b/drivers/block/ataflop.c
@@ -2008,8 +2008,6 @@ 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;
@@ -2020,14 +2018,32 @@ 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]);
                        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)
@@ -2053,11 +2069,6 @@ 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;
@@ -2113,7 +2124,12 @@ 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_out_dma:
        atari_stram_free(DMABuffer);
@@ -2121,9 +2137,6 @@ err:
        while (--i >= 0)
                atari_cleanup_floppy_disk(&unit[i]);
 
-       unregister_blkdev(FLOPPY_MAJOR, "fd");
-out_unlock:
-       mutex_unlock(&ataflop_probe_lock);
        return ret;
 }
 
@@ -2168,14 +2181,8 @@ __setup("floppy=", atari_floppy_setup);
 
 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");
-
-       del_timer_sync(&fd_timer);
-       atari_stram_free( DMABuffer );
+       atari_floppy_cleanup();
 }
 
 module_init(atari_floppy_init)