1 files changed, 30 insertions, 0 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 2621ed2ce6d2..40b17d3b55a1 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1192,6 +1192,30 @@ loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
         return err;
 }
 
+static int loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
+{
+        int err;
+        sector_t sec;
+        loff_t sz;
+
+        err = -ENXIO;
+        if (unlikely(lo->lo_state != Lo_bound))
+                goto out;
+        err = figure_loop_size(lo);
+        if (unlikely(err))
+                goto out;
+        sec = get_capacity(lo->lo_disk);
+        /* the width of sector_t may be narrow for bit-shift */
+        sz = sec;
+        sz <<= 9;
+        mutex_lock(&bdev->bd_mutex);
+        bd_set_size(bdev, sz);
+        mutex_unlock(&bdev->bd_mutex);
+
+ out:
+        return err;
+}
+
 static int lo_ioctl(struct block_device *bdev, fmode_t mode,
         unsigned int cmd, unsigned long arg)
 {
@@ -1224,6 +1248,11 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
         case LOOP_GET_STATUS64:
                 err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
                 break;
+        case LOOP_SET_CAPACITY:
+                err = -EPERM;
+                if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
+                        err = loop_set_capacity(lo, bdev);
+                break;
         default:
                 err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
         }
@@ -1371,6 +1400,7 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
                         lo, (struct compat_loop_info __user *) arg);
                 mutex_unlock(&lo->lo_ctl_mutex);
                 break;
+        case LOOP_SET_CAPACITY:
         case LOOP_CLR_FD:
         case LOOP_GET_STATUS64:
         case LOOP_SET_STATUS64: