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Message-Id: <20211103122157.1215783-12-mcgrof@kernel.org>
Date: Wed, 3 Nov 2021 05:21:55 -0700
From: Luis Chamberlain <mcgrof@...nel.org>
To: axboe@...nel.dk, hch@....de, penguin-kernel@...ove.sakura.ne.jp,
dan.j.williams@...el.com, vishal.l.verma@...el.com,
dave.jiang@...el.com, ira.weiny@...el.com, richard@....at,
miquel.raynal@...tlin.com, vigneshr@...com, efremov@...ux.com,
song@...nel.org, martin.petersen@...cle.com, hare@...e.de,
jack@...e.cz, ming.lei@...hat.com, tj@...nel.org, mcgrof@...nel.org
Cc: linux-mtd@...ts.infradead.org, linux-scsi@...r.kernel.org,
linux-raid@...r.kernel.org, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org,
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
Michael Schmitz <schmitzmic@...il.com>
Subject: [PATCH v2 11/13] ataflop: remove ataflop_probe_lock mutex
From: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
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@...ove.SAKURA.ne.jp>
Fixes: bf9c0538e485b591 ("ataflop: use a separate gendisk for each media format")
Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
Tested-by: Michael Schmitz <schmitzmic@...il.com>
---
drivers/block/ataflop.c | 47 +++++++++++++++++++++++------------------
1 file changed, 27 insertions(+), 20 deletions(-)
diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
index d14bdc3589b2..170dd193cef6 100644
--- 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 @@ static int __init atari_floppy_init (void)
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)
--
2.33.0
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