Commits on Jun 24, 2024

1. feature: block-device mounts …

   This PR adds capability to mount virtual and passthrough disks
   as block devices inside containers.
   
   We add a new "blockdev://" prefix to OCI `Mount.ContainerPath`,
   which indicates that the source should be mounted as a blcok
   device.
   
   A new `BlockDev` field has been added to `mountConfig` used by
   `mountManager`, which indicates that the SCSI attachment should
   be mounted as a block device.
   
   The GCS has also been updated to handle `BlockDev`. Instead of
   mounting the filesystem, GCS creates a symlink to the block device
   corresponding to the SCSI attachment. The symlink path is set
   by shim as a source of bind mount in OCI container spec. GCS
   resolves the symlink and adds the corresponding device cgroup.
   Without the cgroup, the container won't be able to work with the
   block device.
   
   We chose a symlink approach instead of bind mounting the device
   directly, because the shim doesn't know the path at which the
   device will appear inside UVM. For this to work, we either need
   to encode the SCSI controller/LUN in the OCI mount's HostPath or
   update the communication protocol between the shim and GCS, where
   GCS would either return the device path, or add capability for
   the shim to query for it.
   
   Below are some CRI container config examples for physical and
   virtual disks:
   
   Passthrough physical disk:
   ```json
   {
       ...
       "mounts": [
           {
               "host_path": "\\\\.\\PHYSICALDRIVE1",
               "container_path": "blockdev:///my/block/mount",
               "readonly": false
           }
       ]
       ...
   }
   ```
   
   Virtual VHD disk:
   ```json
   {
       ...
       "mounts": [
           {
               "host_path": "C:\\path\\to\\my\\disk.vhdx",
               "container_path": "blockdev:///my/block/mount",
               "readonly": false
           }
       ]
       ...
   }
   ```
   
   Mount manager will differentiate between a block device and a
   filesystem mount. Two containers can use the same managed disk
   inside UVM as a block device or filesystem at the same time.
   For block device mount a symlink will be created, for filesystem
   mount the block device will be mounted in the UVM.
   ```
   bash-5.0# ls -l /run/mounts/scsi/
   total 16
   drwxr-xr-x    3 root     root          4096 Jan  1  1970 m0
   drwxr-xr-x    4 root     root          4096 Jun 20 23:20 m1
   drwxr-xr-x   18 root     root          4096 Jan  1  1970 m2
   drwxr-xr-x    3 root     root          4096 Jun 20 23:20 m3
   lrwxrwxrwx    1 root     root             8 Jun 20 23:22 m4 -> /dev/sde
   bash-5.0# mount | grep sde
   /dev/sde on /run/mounts/scsi/m3 type ext4 (rw,relatime)
   ```
   
   Signed-off-by: Maksim An <maksiman@microsoft.com>

   

   anmaxvl committed Jun 24, 2024
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