Commit 00358933 authored by Tetsuo Handa's avatar Tetsuo Handa Committed by Jens Axboe
Browse files

brd: remove brd_devices_mutex mutex 



If brd_alloc() from brd_probe() is called before brd_alloc() from
brd_init() is called, module loading will fail with -EEXIST error.
To close this race, call __register_blkdev() just before leaving
brd_init().

Then, we can remove brd_devices_mutex mutex, for brd_device list
will no longer be accessed concurrently.

Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/6b074af7-c165-4fab-b7da-8270a4f6f6cd@i-love.sakura.ne.jp


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent a6431e35

drivers/block/brd.c

+30 −43
Original line number Diff line number Diff line
@@ -362,7 +362,6 @@ __setup("ramdisk_size=", ramdisk_size); 
 * (should share code eventually).

 */

static LIST_HEAD(brd_devices);

static DEFINE_MUTEX(brd_devices_mutex);

static struct dentry *brd_debugfs_dir;



static int brd_alloc(int i)
@@ -372,21 +371,14 @@ static int brd_alloc(int i) 
	char buf[DISK_NAME_LEN];

	int err = -ENOMEM;



	mutex_lock(&brd_devices_mutex);

	list_for_each_entry(brd, &brd_devices, brd_list) {

		if (brd->brd_number == i) {

			mutex_unlock(&brd_devices_mutex);

	list_for_each_entry(brd, &brd_devices, brd_list)

		if (brd->brd_number == i)

			return -EEXIST;

		}

	}

	brd = kzalloc(sizeof(*brd), GFP_KERNEL);

	if (!brd) {

		mutex_unlock(&brd_devices_mutex);

	if (!brd)

		return -ENOMEM;

	}

	brd->brd_number		= i;

	list_add_tail(&brd->brd_list, &brd_devices);

	mutex_unlock(&brd_devices_mutex);



	spin_lock_init(&brd->brd_lock);

	INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
@@ -429,9 +421,7 @@ static int brd_alloc(int i) 
out_cleanup_disk:

	blk_cleanup_disk(disk);

out_free_dev:

	mutex_lock(&brd_devices_mutex);

	list_del(&brd->brd_list);

	mutex_unlock(&brd_devices_mutex);

	kfree(brd);

	return err;

}
@@ -441,16 +431,20 @@ static void brd_probe(dev_t dev) 
	brd_alloc(MINOR(dev) / max_part);

}



static void brd_del_one(struct brd_device *brd)

static void brd_cleanup(void)

{

	struct brd_device *brd, *next;



	debugfs_remove_recursive(brd_debugfs_dir);



	list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {

		del_gendisk(brd->brd_disk);

		blk_cleanup_disk(brd->brd_disk);

		brd_free_pages(brd);

	mutex_lock(&brd_devices_mutex);

		list_del(&brd->brd_list);

	mutex_unlock(&brd_devices_mutex);

		kfree(brd);

	}

}



static inline void brd_check_and_reset_par(void)

{
@@ -473,9 +467,18 @@ static inline void brd_check_and_reset_par(void) 


static int __init brd_init(void)

{

	struct brd_device *brd, *next;

	int err, i;



	brd_check_and_reset_par();



	brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL);



	for (i = 0; i < rd_nr; i++) {

		err = brd_alloc(i);

		if (err)

			goto out_free;

	}



	/*

	 * brd module now has a feature to instantiate underlying device

	 * structure on-demand, provided that there is an access dev node.
@@ -491,16 +494,8 @@ static int __init brd_init(void) 
	 *	dynamically.

	 */



	if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe))

		return -EIO;



	brd_check_and_reset_par();



	brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL);



	for (i = 0; i < rd_nr; i++) {

		err = brd_alloc(i);

		if (err)

	if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe)) {

		err = -EIO;

		goto out_free;

	}
@@ -508,11 +503,7 @@ static int __init brd_init(void) 
	return 0;



out_free:

	unregister_blkdev(RAMDISK_MAJOR, "ramdisk");

	debugfs_remove_recursive(brd_debugfs_dir);



	list_for_each_entry_safe(brd, next, &brd_devices, brd_list)

		brd_del_one(brd);

	brd_cleanup();



	pr_info("brd: module NOT loaded !!!\n");

	return err;
@@ -520,13 +511,9 @@ static int __init brd_init(void) 


static void __exit brd_exit(void)

{

	struct brd_device *brd, *next;



	unregister_blkdev(RAMDISK_MAJOR, "ramdisk");

	debugfs_remove_recursive(brd_debugfs_dir);



	list_for_each_entry_safe(brd, next, &brd_devices, brd_list)

		brd_del_one(brd);

	brd_cleanup();



	pr_info("brd: module unloaded\n");

}