Revert "loop: Avoid updating block size under exclusive owner"

Revert commit ce8da5d which is commit
7e49538 upstream.

This reverts commit ce8da5d ("loop: Avoid updating block size under
exclusive owner") for the 6.6 kernel, because if the LTP ioctl_loop06 test is
run with this patch in place, the test will fail, it leaves the host unable to
kexec into the kernel again (hangs forever) and "losetup -a" will hang on
attempting to access the /dev/loopN device that the test has set up.

The patch doesn't need to be reverted from 6.12, as it works fine there.

Cc: stable@vger.kernel.org # 6.6.x
Signed-off-by: Eric Hagberg <ehagberg@janestreet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Eric Hagberg

drivers/block/loop.c

@@ -1472,36 +1472,19 @@ static int loop_set_dio(struct loop_device *lo, unsigned long arg)
 	return error;
 }
 
-static int loop_set_block_size(struct loop_device *lo, blk_mode_t mode,
-			       struct block_device *bdev, unsigned long arg)
+static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
 {
 	int err = 0;
 
-	/*
-	 * If we don't hold exclusive handle for the device, upgrade to it
-	 * here to avoid changing device under exclusive owner.
-	 */
-	if (!(mode & BLK_OPEN_EXCL)) {
-		err = bd_prepare_to_claim(bdev, loop_set_block_size, NULL);
-		if (err)
-			return err;
-	}
-
-	err = mutex_lock_killable(&lo->lo_mutex);
-	if (err)
-		goto abort_claim;
-
-	if (lo->lo_state != Lo_bound) {
-		err = -ENXIO;
-		goto unlock;
-	}
+	if (lo->lo_state != Lo_bound)
+		return -ENXIO;
 
 	err = blk_validate_block_size(arg);
 	if (err)
 		return err;
 
 	if (lo->lo_queue->limits.logical_block_size == arg)
-		goto unlock;
+		return 0;
 
 	sync_blockdev(lo->lo_device);
 	invalidate_bdev(lo->lo_device);
@@ -1513,11 +1496,6 @@ static int loop_set_block_size(struct loop_device *lo, blk_mode_t mode,
 	loop_update_dio(lo);
 	blk_mq_unfreeze_queue(lo->lo_queue);
 
-unlock:
-	mutex_unlock(&lo->lo_mutex);
-abort_claim:
-	if (!(mode & BLK_OPEN_EXCL))
-		bd_abort_claiming(bdev, loop_set_block_size);
 	return err;
 }
 
@@ -1536,6 +1514,9 @@ static int lo_simple_ioctl(struct loop_device *lo, unsigned int cmd,
 	case LOOP_SET_DIRECT_IO:
 		err = loop_set_dio(lo, arg);
 		break;
+	case LOOP_SET_BLOCK_SIZE:
+		err = loop_set_block_size(lo, arg);
+		break;
 	default:
 		err = -EINVAL;
 	}
@@ -1590,12 +1571,9 @@ static int lo_ioctl(struct block_device *bdev, blk_mode_t mode,
 		break;
 	case LOOP_GET_STATUS64:
 		return loop_get_status64(lo, argp);
-	case LOOP_SET_BLOCK_SIZE:
-		if (!(mode & BLK_OPEN_WRITE) && !capable(CAP_SYS_ADMIN))
-			return -EPERM;
-		return loop_set_block_size(lo, mode, bdev, arg);
 	case LOOP_SET_CAPACITY:
 	case LOOP_SET_DIRECT_IO:
+	case LOOP_SET_BLOCK_SIZE:
 		if (!(mode & BLK_OPEN_WRITE) && !capable(CAP_SYS_ADMIN))
 			return -EPERM;
 		fallthrough;