[PATCH 16/19] ataflop: use a separate gendisk for each media format

Christoph Hellwig
2020-08-30T06:26:29Z

The Atari floppy driver usually autodetects the media when used with the
ormal /dev/fd? devices, which also are the only nodes created by udev.
But it also supports various aliases that force a given media format.
That is currently supported using the blk_register_region framework
which finds the floppy gendisk even for a 'mismatched' dev_t. The
problem with this (besides the code complexity) is that it creates
multiple struct block_device instances for the whole device of a
single gendisk, which can lead to interesting issues in code not
aware of that fact.

To fix this just create a separate gendisk for each of the aliases
if they are accessed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/block/ataflop.c | 135 +++++++++++++++++++++++++---------------
1 file changed, 86 insertions(+), 49 deletions(-)

diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
index a50e13af030526..b5acc85328c329 100644
--- a/drivers/block/ataflop.c
+++ b/drivers/block/ataflop.c
@@ -297,7 +297,7 @@ static struct atari_floppy_struct {
unsigned int wpstat; /* current state of WP signal (for
disk change detection) */
int flags; /* flags */
- struct gendisk *disk;
+ struct gendisk *disk[NUM_DISK_MINORS];
int ref;
int type;
struct blk_mq_tag_set tag_set;
@@ -723,12 +723,16 @@ static void fd_error( void )

static int do_format(int drive, int type, struct atari_format_descr *desc)
{
- struct request_queue *q = unit[drive].disk->queue;
+ struct request_queue *q;
unsigned char *p;
int sect, nsect;
unsigned long flags;
int ret;

+ if (type)
+ type--;
+
+ q = unit[drive].disk[type]->queue;
blk_mq_freeze_queue(q);
blk_mq_quiesce_queue(q);

@@ -738,7 +742,7 @@ static int do_format(int drive, int type, struct atari_format_descr *desc)
local_irq_restore(flags);

if (type) {
- if (--type >= NUM_DISK_MINORS ||
+ if (type >= NUM_DISK_MINORS ||
minor2disktype[type].drive_types > DriveType) {
ret = -EINVAL;
goto out;
@@ -1154,7 +1158,7 @@ static void fd_rwsec_done1(int status)
if (SUDT[-1].blocks > ReqBlock) {
/* try another disk type */
SUDT--;
- set_capacity(unit[SelectedDrive].disk,
+ set_capacity(unit[SelectedDrive].disk[0],
SUDT->blocks);
} else
Probing = 0;
@@ -1169,7 +1173,7 @@ static void fd_rwsec_done1(int status)
/* record not found, but not probing. Maybe stretch wrong ? Restart probing */
if (SUD.autoprobe) {
SUDT = atari_disk_type + StartDiskType[DriveType];
- set_capacity(unit[SelectedDrive].disk,
+ set_capacity(unit[SelectedDrive].disk[0],
SUDT->blocks);
Probing = 1;
}
@@ -1515,7 +1519,7 @@ static blk_status_t ataflop_queue_rq(struct blk_mq_hw_ctx *hctx,
if (!UDT) {
Probing = 1;
UDT = atari_disk_type + StartDiskType[DriveType];
- set_capacity(floppy->disk, UDT->blocks);
+ set_capacity(bd->rq->rq_disk, UDT->blocks);
UD.autoprobe = 1;
}
}
@@ -1533,7 +1537,7 @@ static blk_status_t ataflop_queue_rq(struct blk_mq_hw_ctx *hctx,
}
type = minor2disktype[type].index;
UDT = &atari_disk_type[type];
- set_capacity(floppy->disk, UDT->blocks);
+ set_capacity(bd->rq->rq_disk, UDT->blocks);
UD.autoprobe = 0;
}

@@ -1658,7 +1662,7 @@ static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode,
printk (KERN_INFO "floppy%d: setting %s %p!\n",
drive, dtp->name, dtp);
UDT = dtp;
- set_capacity(floppy->disk, UDT->blocks);
+ set_capacity(disk, UDT->blocks);

if (cmd == FDDEFPRM) {
/* save settings as permanent default type */
@@ -1702,7 +1706,7 @@ static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode,
return -EINVAL;

UDT = dtp;
- set_capacity(floppy->disk, UDT->blocks);
+ set_capacity(disk, UDT->blocks);

return 0;
case FDMSGON:
@@ -1725,7 +1729,7 @@ static int fd_locked_ioctl(struct block_device *bdev, fmode_t mode,
UDT = NULL;
/* MSch: invalidate default_params */
default_params[drive].blocks = 0;
- set_capacity(floppy->disk, MAX_DISK_SIZE * 2);
+ set_capacity(disk, MAX_DISK_SIZE * 2);
fallthrough;
case FDFMTEND:
case FDFLUSH:
@@ -1961,14 +1965,50 @@ static const struct blk_mq_ops ataflop_mq_ops = {
.commit_rqs = ataflop_commit_rqs,
};

-static struct kobject *floppy_find(dev_t dev, int *part, void *data)
+static int ataflop_alloc_disk(unsigned int drive, unsigned int type)
{
- int drive = *part & 3;
- int type = *part >> 2;
+ struct gendisk *disk;
+ int ret;
+
+ disk = alloc_disk(1);
+ if (!disk)
+ return -ENOMEM;
+
+ disk->queue = blk_mq_init_queue(&unit[drive].tag_set);
+ if (IS_ERR(disk->queue)) {
+ ret = PTR_ERR(disk->queue);
+ disk->queue = NULL;
+ put_disk(disk);
+ return ret;
+ }
+
+ disk->major = FLOPPY_MAJOR;
+ disk->first_minor = drive + (type << 2);
+ sprintf(disk->disk_name, "fd%d", drive);
+ disk->fops = &floppy_fops;
+ disk->events = DISK_EVENT_MEDIA_CHANGE;
+ disk->private_data = &unit[drive];
+ set_capacity(disk, MAX_DISK_SIZE * 2);
+
+ unit[drive].disk[type] = disk;
+ return 0;
+}
+
+static DEFINE_MUTEX(ataflop_probe_lock);
+
+static void ataflop_probe(dev_t dev)
+{
+ int drive = MINOR(dev) & 3;
+ int type = MINOR(dev) >> 2;
+
if (drive >= FD_MAX_UNITS || type > NUM_DISK_MINORS)
- return NULL;
- *part = 0;
- return get_disk_and_module(unit[drive].disk);
+ 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 int __init atari_floppy_init (void)
@@ -1980,23 +2020,26 @@ static int __init atari_floppy_init (void)
/* Amiga, Mac, ... don't have Atari-compatible floppy :-) */
return -ENODEV;

- if (register_blkdev(FLOPPY_MAJOR,"fd"))
- return -EBUSY;
+ 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++) {
- unit[i].disk = alloc_disk(1);
- if (!unit[i].disk) {
- ret = -ENOMEM;
+ memset(&unit[i].tag_set, 0, sizeof(unit[i].tag_set));
+ unit[i].tag_set.ops = &ataflop_mq_ops;
+ unit[i].tag_set.nr_hw_queues = 1;
+ unit[i].tag_set.nr_maps = 1;
+ unit[i].tag_set.queue_depth = 2;
+ unit[i].tag_set.numa_node = NUMA_NO_NODE;
+ unit[i].tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
+ ret = blk_mq_alloc_tag_set(&unit[i].tag_set);
+ if (ret)
goto err;
- }

- unit[i].disk->queue = blk_mq_init_sq_queue(&unit[i].tag_set,
- &ataflop_mq_ops, 2,
- BLK_MQ_F_SHOULD_MERGE);
- if (IS_ERR(unit[i].disk->queue)) {
- put_disk(unit[i].disk);
- ret = PTR_ERR(unit[i].disk->queue);
- unit[i].disk->queue = NULL;
+ ret = ataflop_alloc_disk(i, 0);
+ if (ret) {
+ blk_mq_free_tag_set(&unit[i].tag_set);
goto err;
}
}
@@ -2026,19 +2069,9 @@ static int __init atari_floppy_init (void)
for (i = 0; i < FD_MAX_UNITS; i++) {
unit[i].track = -1;
unit[i].flags = 0;
- unit[i].disk->major = FLOPPY_MAJOR;
- unit[i].disk->first_minor = i;
- sprintf(unit[i].disk->disk_name, "fd%d", i);
- unit[i].disk->fops = &floppy_fops;
- unit[i].disk->events = DISK_EVENT_MEDIA_CHANGE;
- unit[i].disk->private_data = &unit[i];
- set_capacity(unit[i].disk, MAX_DISK_SIZE * 2);
- add_disk(unit[i].disk);
+ add_disk(unit[i].disk[0]);
}

- blk_register_region(MKDEV(FLOPPY_MAJOR, 0), 256, THIS_MODULE,
- floppy_find, NULL, NULL);
-
printk(KERN_INFO "Atari floppy driver: max. %cD, %strack buffering\n",
DriveType == 0 ? 'D' : DriveType == 1 ? 'H' : 'E',
UseTrackbuffer ? "" : "no ");
@@ -2048,14 +2081,14 @@ static int __init atari_floppy_init (void)

err:
while (--i >= 0) {
- struct gendisk *disk = unit[i].disk;
-
- blk_cleanup_queue(disk->queue);
+ blk_cleanup_queue(unit[i].disk[0]->queue);
+ put_disk(unit[i].disk[0]);
blk_mq_free_tag_set(&unit[i].tag_set);
- put_disk(unit[i].disk);
}

unregister_blkdev(FLOPPY_MAJOR, "fd");
+out_unlock:
+ mutex_unlock(&ataflop_probe_lock);
return ret;
}

@@ -2100,13 +2133,17 @@ __setup("floppy=", atari_floppy_setup);

static void __exit atari_floppy_exit(void)
{
- int i;
- blk_unregister_region(MKDEV(FLOPPY_MAJOR, 0), 256);
+ int i, type;
+
for (i = 0; i < FD_MAX_UNITS; i++) {
- del_gendisk(unit[i].disk);
- blk_cleanup_queue(unit[i].disk->queue);
+ 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);
- put_disk(unit[i].disk);
}
unregister_blkdev(FLOPPY_MAJOR, "fd");

--
2.28.0