Storage ballooning in a mobile computing device

A computing system for managing storage space in a mobile computing device having a host system and a guest system that share storage resources, the system comprising:

• one or more processors,
• a non-transitory computer-readable medium coupled to the one or more processors having instructions stored thereon that, when executed by the one or more processors, cause the one or more processors to perform operations comprising:
• detecting a decrease in available disk space in a host file system in the mobile computing device, wherein an image file for the guest system in the mobile computing device is stored in the host file system;
• in response to the detected decrease, issuing a request for increasing a virtual size of a balloon file in a guest file system of the guest system such that a ratio of the virtual balloon file size to an amount of host physical storage space occupied by applications or components in the host file system, other than space allocated to the guest system, is maintained equal to or more than one to one without increasing an actual size of the balloon file;
• and
• at the host system, in response to the increased virtual size of the balloon file, detecting data blocks that are written with a predetermined content by the guest system in response to a communication from the guest system regarding the data blocks being written with the predetermined content and freeing a host physical storage associated with the detected data blocks by storing a metadata record to indicate that the host physical storage associated with the detected data blocks contains the predetermined content without writing the predetermined content onto the host physical storage, thereby causing a size of the image file for the guest system to be reduced.

A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for managing storage space in a mobile computing device having a host system and a guest system that share storage resources, the method comprising:

• detecting a decrease in available disk space in a host file system in the mobile computing device, wherein an image file for the guest system in the mobile computing device is stored in the host file system;
• in response to the detected decrease, issuing a request for increasing a virtual size of a balloon file in a guest file system of the guest system such that a ratio of the virtual balloon file size to an amount of host physical storage space occupied by applications or components in the host file system, other than space allocated to the guest system, is maintained equal to or more than one to one without increasing an actual size of the balloon file;
• and
• at the host system, in response to the increased virtual size of the balloon file, detecting data blocks that are written with a predetermined content by the guest system in response to a communication from the guest system regarding the data blocks being written with the predetermined content and freeing a host physical storage associated with the detected data blocks by storing a metadata record to indicate that the host physical storage associated with the detected data blocks contains the predetermined content without writing the predetermined content onto the host physical storage, thereby causing a size of the image file for the guest system to be reduced.