Revert "block/loop: Use global lock for ioctl() operation."

This reverts commit 57da9a9742200f391d1cf93fea389f7ddc25ec9a which is
commit 310ca162d779efee8a2dc3731439680f3e9c1e86 upstream.

Jan Kara has reported seeing problems with this patch applied, as has
Salvatore Bonaccorso, so let's drop it for now.

Reported-by: Salvatore Bonaccorso <carnil@debian.org>
Reported-by: Jan Kara <jack@suse.cz>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 30 insertions, 29 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 24a3fb35614f..bd447de4a5b8 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -82,7 +82,6 @@
 
 static DEFINE_IDR(loop_index_idr);
 static DEFINE_MUTEX(loop_index_mutex);
-static DEFINE_MUTEX(loop_ctl_mutex);
 
 static int max_part;
 static int part_shift;
@@ -1019,7 +1018,7 @@ static int loop_clr_fd(struct loop_device *lo)
 	 */
 	if (atomic_read(&lo->lo_refcnt) > 1) {
 		lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
-		mutex_unlock(&loop_ctl_mutex);
+		mutex_unlock(&lo->lo_ctl_mutex);
 		return 0;
 	}
 
@@ -1071,12 +1070,12 @@ static int loop_clr_fd(struct loop_device *lo)
 	if (!part_shift)
 		lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
 	loop_unprepare_queue(lo);
-	mutex_unlock(&loop_ctl_mutex);
+	mutex_unlock(&lo->lo_ctl_mutex);
 	/*
-	 * Need not hold loop_ctl_mutex to fput backing file.
-	 * Calling fput holding loop_ctl_mutex triggers a circular
+	 * Need not hold lo_ctl_mutex to fput backing file.
+	 * Calling fput holding lo_ctl_mutex triggers a circular
 	 * lock dependency possibility warning as fput can take
-	 * bd_mutex which is usually taken before loop_ctl_mutex.
+	 * bd_mutex which is usually taken before lo_ctl_mutex.
 	 */
 	fput(filp);
 	return 0;
@@ -1195,7 +1194,7 @@ loop_get_status(struct loop_device *lo, struct loop_info64 *info)
 	int ret;
 
 	if (lo->lo_state != Lo_bound) {
-		mutex_unlock(&loop_ctl_mutex);
+		mutex_unlock(&lo->lo_ctl_mutex);
 		return -ENXIO;
 	}
 
@@ -1214,10 +1213,10 @@ loop_get_status(struct loop_device *lo, struct loop_info64 *info)
 		       lo->lo_encrypt_key_size);
 	}
 
-	/* Drop loop_ctl_mutex while we call into the filesystem. */
+	/* Drop lo_ctl_mutex while we call into the filesystem. */
 	path = lo->lo_backing_file->f_path;
 	path_get(&path);
-	mutex_unlock(&loop_ctl_mutex);
+	mutex_unlock(&lo->lo_ctl_mutex);
 	ret = vfs_getattr(&path, &stat, STATX_INO, AT_STATX_SYNC_AS_STAT);
 	if (!ret) {
 		info->lo_device = huge_encode_dev(stat.dev);
@@ -1309,7 +1308,7 @@ loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) {
 	int err;
 
 	if (!arg) {
-		mutex_unlock(&loop_ctl_mutex);
+		mutex_unlock(&lo->lo_ctl_mutex);
 		return -EINVAL;
 	}
 	err = loop_get_status(lo, &info64);
@@ -1327,7 +1326,7 @@ loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
 	int err;
 
 	if (!arg) {
-		mutex_unlock(&loop_ctl_mutex);
+		mutex_unlock(&lo->lo_ctl_mutex);
 		return -EINVAL;
 	}
 	err = loop_get_status(lo, &info64);
@@ -1402,7 +1401,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
 	struct loop_device *lo = bdev->bd_disk->private_data;
 	int err;
 
-	mutex_lock_nested(&loop_ctl_mutex, 1);
+	mutex_lock_nested(&lo->lo_ctl_mutex, 1);
 	switch (cmd) {
 	case LOOP_SET_FD:
 		err = loop_set_fd(lo, mode, bdev, arg);
@@ -1411,7 +1410,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
 		err = loop_change_fd(lo, bdev, arg);
 		break;
 	case LOOP_CLR_FD:
-		/* loop_clr_fd would have unlocked loop_ctl_mutex on success */
+		/* loop_clr_fd would have unlocked lo_ctl_mutex on success */
 		err = loop_clr_fd(lo);
 		if (!err)
 			goto out_unlocked;
@@ -1424,7 +1423,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
 		break;
 	case LOOP_GET_STATUS:
 		err = loop_get_status_old(lo, (struct loop_info __user *) arg);
-		/* loop_get_status() unlocks loop_ctl_mutex */
+		/* loop_get_status() unlocks lo_ctl_mutex */
 		goto out_unlocked;
 	case LOOP_SET_STATUS64:
 		err = -EPERM;
@@ -1434,7 +1433,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
 		break;
 	case LOOP_GET_STATUS64:
 		err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
-		/* loop_get_status() unlocks loop_ctl_mutex */
+		/* loop_get_status() unlocks lo_ctl_mutex */
 		goto out_unlocked;
 	case LOOP_SET_CAPACITY:
 		err = -EPERM;
@@ -1454,7 +1453,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
 	default:
 		err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
 	}
-	mutex_unlock(&loop_ctl_mutex);
+	mutex_unlock(&lo->lo_ctl_mutex);
 
 out_unlocked:
 	return err;
@@ -1571,7 +1570,7 @@ loop_get_status_compat(struct loop_device *lo,
 	int err;
 
 	if (!arg) {
-		mutex_unlock(&loop_ctl_mutex);
+		mutex_unlock(&lo->lo_ctl_mutex);
 		return -EINVAL;
 	}
 	err = loop_get_status(lo, &info64);
@@ -1588,16 +1587,16 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
 
 	switch(cmd) {
 	case LOOP_SET_STATUS:
-		mutex_lock(&loop_ctl_mutex);
+		mutex_lock(&lo->lo_ctl_mutex);
 		err = loop_set_status_compat(
 			lo, (const struct compat_loop_info __user *) arg);
-		mutex_unlock(&loop_ctl_mutex);
+		mutex_unlock(&lo->lo_ctl_mutex);
 		break;
 	case LOOP_GET_STATUS:
-		mutex_lock(&loop_ctl_mutex);
+		mutex_lock(&lo->lo_ctl_mutex);
 		err = loop_get_status_compat(
 			lo, (struct compat_loop_info __user *) arg);
-		/* loop_get_status() unlocks loop_ctl_mutex */
+		/* loop_get_status() unlocks lo_ctl_mutex */
 		break;
 	case LOOP_SET_CAPACITY:
 	case LOOP_CLR_FD:
@@ -1641,7 +1640,7 @@ static void __lo_release(struct loop_device *lo)
 	if (atomic_dec_return(&lo->lo_refcnt))
 		return;
 
-	mutex_lock(&loop_ctl_mutex);
+	mutex_lock(&lo->lo_ctl_mutex);
 	if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
 		/*
 		 * In autoclear mode, stop the loop thread
@@ -1659,7 +1658,7 @@ static void __lo_release(struct loop_device *lo)
 		blk_mq_unfreeze_queue(lo->lo_queue);
 	}
 
-	mutex_unlock(&loop_ctl_mutex);
+	mutex_unlock(&lo->lo_ctl_mutex);
 }
 
 static void lo_release(struct gendisk *disk, fmode_t mode)
@@ -1705,10 +1704,10 @@ static int unregister_transfer_cb(int id, void *ptr, void *data)
 	struct loop_device *lo = ptr;
 	struct loop_func_table *xfer = data;
 
-	mutex_lock(&loop_ctl_mutex);
+	mutex_lock(&lo->lo_ctl_mutex);
 	if (lo->lo_encryption == xfer)
 		loop_release_xfer(lo);
-	mutex_unlock(&loop_ctl_mutex);
+	mutex_unlock(&lo->lo_ctl_mutex);
 	return 0;
 }
 
@@ -1881,6 +1880,7 @@ static int loop_add(struct loop_device **l, int i)
 	if (!part_shift)
 		disk->flags |= GENHD_FL_NO_PART_SCAN;
 	disk->flags |= GENHD_FL_EXT_DEVT;
+	mutex_init(&lo->lo_ctl_mutex);
 	atomic_set(&lo->lo_refcnt, 0);
 	lo->lo_number		= i;
 	spin_lock_init(&lo->lo_lock);
@@ -1993,19 +1993,19 @@ static long loop_control_ioctl(struct file *file, unsigned int cmd,
 		ret = loop_lookup(&lo, parm);
 		if (ret < 0)
 			break;
-		mutex_lock(&loop_ctl_mutex);
+		mutex_lock(&lo->lo_ctl_mutex);
 		if (lo->lo_state != Lo_unbound) {
 			ret = -EBUSY;
-			mutex_unlock(&loop_ctl_mutex);
+			mutex_unlock(&lo->lo_ctl_mutex);
 			break;
 		}
 		if (atomic_read(&lo->lo_refcnt) > 0) {
 			ret = -EBUSY;
-			mutex_unlock(&loop_ctl_mutex);
+			mutex_unlock(&lo->lo_ctl_mutex);
 			break;
 		}
 		lo->lo_disk->private_data = NULL;
-		mutex_unlock(&loop_ctl_mutex);
+		mutex_unlock(&lo->lo_ctl_mutex);
 		idr_remove(&loop_index_idr, lo->lo_number);
 		loop_remove(lo);
 		break;
diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index b2251752452b..dfc54ceba410 100644
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -54,6 +54,7 @@ struct loop_device {
 
 	spinlock_t		lo_lock;
 	int			lo_state;
+	struct mutex		lo_ctl_mutex;
 	struct kthread_worker	worker;
 	struct task_struct	*worker_task;
 	bool			use_dio;