[PATCH 14/19] floppy: use a separate gendisk for each media format

Christoph Hellwig
2020-08-30T06:26:23Z

The floppy driver usually autodetects the media when used with the
normal /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/floppy.c | 154 ++++++++++++++++++++++++++---------------
1 file changed, 97 insertions(+), 57 deletions(-)

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index a563b023458a8b..adf2b4dbd1ea09 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -402,7 +402,6 @@ static struct floppy_drive_params drive_params[N_DRIVE];
static struct floppy_drive_struct drive_state[N_DRIVE];
static struct floppy_write_errors write_errors[N_DRIVE];
static struct timer_list motor_off_timer[N_DRIVE];
-static struct gendisk *disks[N_DRIVE];
static struct blk_mq_tag_set tag_sets[N_DRIVE];
static struct block_device *opened_bdev[N_DRIVE];
static DEFINE_MUTEX(open_lock);
@@ -477,6 +476,8 @@ static struct floppy_struct floppy_type[32] = {
{ 3200,20,2,80,0,0x1C,0x00,0xCF,0x2C,"H1600" }, /* 31 1.6MB 3.5" */
};

+static struct gendisk *disks[N_DRIVE][ARRAY_SIZE(floppy_type)];
+
#define SECTSIZE (_FD_SECTSIZE(*floppy))

/* Auto-detection: Disk type used until the next media change occurs. */
@@ -4109,7 +4110,7 @@ static int floppy_open(struct block_device *bdev, fmode_t mode)

new_dev = MINOR(bdev->bd_dev);
drive_state[drive].fd_device = new_dev;
- set_capacity(disks[drive], floppy_sizes[new_dev]);
+ set_capacity(disks[drive][ITYPE(new_dev)], floppy_sizes[new_dev]);
if (old_dev != -1 && old_dev != new_dev) {
if (buffer_drive == drive)
buffer_track = -1;
@@ -4577,15 +4578,58 @@ static bool floppy_available(int drive)
return true;
}

-static struct kobject *floppy_find(dev_t dev, int *part, void *data)
+static int floppy_alloc_disk(unsigned int drive, unsigned int type)
{
- int drive = (*part & 3) | ((*part & 0x80) >> 5);
- if (drive >= N_DRIVE || !floppy_available(drive))
- return NULL;
- if (((*part >> 2) & 0x1f) >= ARRAY_SIZE(floppy_type))
- return NULL;
- *part = 0;
- return get_disk_and_module(disks[drive]);
+ struct gendisk *disk;
+ int err;
+
+ disk = alloc_disk(1);
+ if (!disk)
+ return -ENOMEM;
+
+ disk->queue = blk_mq_init_queue(&tag_sets[drive]);
+ if (IS_ERR(disk->queue)) {
+ err = PTR_ERR(disk);
+ disk->queue = NULL;
+ put_disk(disk);
+ return err;
+ }
+
+ blk_queue_bounce_limit(disk->queue, BLK_BOUNCE_HIGH);
+ blk_queue_max_hw_sectors(disk->queue, 64);
+ disk->major = FLOPPY_MAJOR;
+ disk->first_minor = TOMINOR(drive) | (type << 2);
+ disk->fops = &floppy_fops;
+ disk->events = DISK_EVENT_MEDIA_CHANGE;
+ if (type)
+ sprintf(disk->disk_name, "fd%d_type%d", drive, type);
+ else
+ sprintf(disk->disk_name, "fd%d", drive);
+ /* to be cleaned up... */
+ disk->private_data = (void *)(long)drive;
+ disk->flags |= GENHD_FL_REMOVABLE;
+
+ disks[drive][type] = disk;
+ return 0;
+}
+
+static DEFINE_MUTEX(floppy_probe_lock);
+
+static void floppy_probe(dev_t dev)
+{
+ unsigned int drive = (MINOR(dev) & 3) | ((MINOR(dev) & 0x80) >> 5);
+ unsigned int type = (MINOR(dev) >> 2) & 0x1f;
+
+ if (drive >= N_DRIVE || !floppy_available(drive) ||
+ type >= ARRAY_SIZE(floppy_type))
+ return;
+
+ mutex_lock(&floppy_probe_lock);
+ if (!disks[drive][type]) {
+ if (floppy_alloc_disk(drive, type) == 0)
+ add_disk(disks[drive][type]);
+ }
+ mutex_unlock(&floppy_probe_lock);
}

static int __init do_floppy_init(void)
@@ -4607,33 +4651,25 @@ static int __init do_floppy_init(void)
return -ENOMEM;

for (drive = 0; drive < N_DRIVE; drive++) {
- disks[drive] = alloc_disk(1);
- if (!disks[drive]) {
- err = -ENOMEM;
+ memset(&tag_sets[drive], 0, sizeof(tag_sets[drive]));
+ tag_sets[drive].ops = &floppy_mq_ops;
+ tag_sets[drive].nr_hw_queues = 1;
+ tag_sets[drive].nr_maps = 1;
+ tag_sets[drive].queue_depth = 2;
+ tag_sets[drive].numa_node = NUMA_NO_NODE;
+ tag_sets[drive].flags = BLK_MQ_F_SHOULD_MERGE;
+ err = blk_mq_alloc_tag_set(&tag_sets[drive]);
+ if (err)
goto out_put_disk;
- }

- disks[drive]->queue = blk_mq_init_sq_queue(&tag_sets[drive],
- &floppy_mq_ops, 2,
- BLK_MQ_F_SHOULD_MERGE);
- if (IS_ERR(disks[drive]->queue)) {
- err = PTR_ERR(disks[drive]->queue);
- disks[drive]->queue = NULL;
+ err = floppy_alloc_disk(drive, 0);
+ if (err)
goto out_put_disk;
- }
-
- blk_queue_bounce_limit(disks[drive]->queue, BLK_BOUNCE_HIGH);
- blk_queue_max_hw_sectors(disks[drive]->queue, 64);
- disks[drive]->major = FLOPPY_MAJOR;
- disks[drive]->first_minor = TOMINOR(drive);
- disks[drive]->fops = &floppy_fops;
- disks[drive]->events = DISK_EVENT_MEDIA_CHANGE;
- sprintf(disks[drive]->disk_name, "fd%d", drive);

timer_setup(&motor_off_timer[drive], motor_off_callback, 0);
}

- err = register_blkdev(FLOPPY_MAJOR, "fd");
+ err = __register_blkdev(FLOPPY_MAJOR, "fd", floppy_probe);
if (err)
goto out_put_disk;

@@ -4641,9 +4677,6 @@ static int __init do_floppy_init(void)
if (err)
goto out_unreg_blkdev;

- blk_register_region(MKDEV(FLOPPY_MAJOR, 0), 256, THIS_MODULE,
- floppy_find, NULL, NULL);
-
for (i = 0; i < 256; i++)
if (ITYPE(i))
floppy_sizes[i] = floppy_type[ITYPE(i)].size;
@@ -4671,7 +4704,7 @@ static int __init do_floppy_init(void)
if (fdc_state[0].address == -1) {
cancel_delayed_work(&fd_timeout);
err = -ENODEV;
- goto out_unreg_region;
+ goto out_unreg_driver;
}
#if N_FDC > 1
fdc_state[1].address = FDC2;
@@ -4682,7 +4715,7 @@ static int __init do_floppy_init(void)
if (err) {
cancel_delayed_work(&fd_timeout);
err = -EBUSY;
- goto out_unreg_region;
+ goto out_unreg_driver;
}

/* initialise drive state */
@@ -4759,10 +4792,8 @@ static int __init do_floppy_init(void)
if (err)
goto out_remove_drives;

- /* to be cleaned up... */
- disks[drive]->private_data = (void *)(long)drive;
- disks[drive]->flags |= GENHD_FL_REMOVABLE;
- device_add_disk(&floppy_device[drive].dev, disks[drive], NULL);
+ device_add_disk(&floppy_device[drive].dev, disks[drive][0],
+ NULL);
}

return 0;
@@ -4770,30 +4801,27 @@ static int __init do_floppy_init(void)
out_remove_drives:
while (drive--) {
if (floppy_available(drive)) {
- del_gendisk(disks[drive]);
+ del_gendisk(disks[drive][0]);
platform_device_unregister(&floppy_device[drive]);
}
}
out_release_dma:
if (atomic_read(&usage_count))
floppy_release_irq_and_dma();
-out_unreg_region:
- blk_unregister_region(MKDEV(FLOPPY_MAJOR, 0), 256);
+out_unreg_driver:
platform_driver_unregister(&floppy_driver);
out_unreg_blkdev:
unregister_blkdev(FLOPPY_MAJOR, "fd");
out_put_disk:
destroy_workqueue(floppy_wq);
for (drive = 0; drive < N_DRIVE; drive++) {
- if (!disks[drive])
+ if (!disks[drive][0])
break;
- if (disks[drive]->queue) {
- del_timer_sync(&motor_off_timer[drive]);
- blk_cleanup_queue(disks[drive]->queue);
- disks[drive]->queue = NULL;
- blk_mq_free_tag_set(&tag_sets[drive]);
- }
- put_disk(disks[drive]);
+ del_timer_sync(&motor_off_timer[drive]);
+ blk_cleanup_queue(disks[drive][0]->queue);
+ disks[drive][0]->queue = NULL;
+ blk_mq_free_tag_set(&tag_sets[drive]);
+ put_disk(disks[drive][0]);
}
return err;
}
@@ -5004,9 +5032,8 @@ module_init(floppy_module_init);

static void __exit floppy_module_exit(void)
{
- int drive;
+ int drive, i;

- blk_unregister_region(MKDEV(FLOPPY_MAJOR, 0), 256);
unregister_blkdev(FLOPPY_MAJOR, "fd");
platform_driver_unregister(&floppy_driver);

@@ -5016,10 +5043,16 @@ static void __exit floppy_module_exit(void)
del_timer_sync(&motor_off_timer[drive]);

if (floppy_available(drive)) {
- del_gendisk(disks[drive]);
+ for (i = 0; i < ARRAY_SIZE(floppy_type); i++) {
+ if (disks[drive][i])
+ del_gendisk(disks[drive][i]);
+ }
platform_device_unregister(&floppy_device[drive]);
}
- blk_cleanup_queue(disks[drive]->queue);
+ for (i = 0; i < ARRAY_SIZE(floppy_type); i++) {
+ if (disks[drive][i])
+ blk_cleanup_queue(disks[drive][i]->queue);
+ }
blk_mq_free_tag_set(&tag_sets[drive]);

/*
@@ -5027,10 +5060,17 @@ static void __exit floppy_module_exit(void)
* queue reference in put_disk().
*/
if (!(allowed_drive_mask & (1 << drive)) ||
- fdc_state[FDC(drive)].version == FDC_NONE)
- disks[drive]->queue = NULL;
+ fdc_state[FDC(drive)].version == FDC_NONE) {
+ for (i = 0; i < ARRAY_SIZE(floppy_type); i++) {
+ if (disks[drive][i])
+ disks[drive][i]->queue = NULL;
+ }
+ }

- put_disk(disks[drive]);
+ for (i = 0; i < ARRAY_SIZE(floppy_type); i++) {
+ if (disks[drive][i])
+ put_disk(disks[drive][i]);
+ }
}

cancel_delayed_work_sync(&fd_timeout);
--
2.28.0