Overlay size option: --overlay2=all:memory,size=1g

[stepancheg]

Implement #11504.

Add optional size= parameter to --overlay2 flag: when it is set, overlay upper layer is mounted with given size flag.

Tested:

sudo bazel-bin/runsc/runsc_/runsc --overlay2=all:memory,size=1m run --bundle ~/bu cont-i

root@:/# dd if=/dev/urandom of=/x bs=1k count=1000
1000+0 records in
1000+0 records out
1024000 bytes (1.0 MB, 1000 KiB) copied, 0.0109061 s, 93.9 MB/s

root@:/# dd if=/dev/urandom of=/x bs=1k count=1100
dd: error writing '/x': No space left on device
1021+0 records in
1020+0 records out
1044480 bytes (1.0 MB, 1020 KiB) copied, 0.011396 s, 91.7 MB/s

  -overlay
        DEPRECATED: use --overlay2=all:memory to achieve the same effect
  -overlay2 value
        wrap mounts with overlayfs. Format is
        * 'none' to turn overlay mode off
        * {mount}:{medium}[size={size}], where
            'mount' can be 'root' or 'all'
            'medium' can be 'memory', 'self' or 'dir=/abs/dir/path' in which filestore will be created
            'size' optional parameter overrides default overlay upper layer size
         (default root:self)
  -panic-log string
        file path where panic reports and other Go's runtime messages are written.

[stepancheg]

Changed syntax from

--overlay2=all:memory:size=1g

to

--overlay2=all:memory,size=1g

[ayushr2]

Please see the discussion in #11504. I'd prefer not to complicate the --overlay2 flag any further. If you really want to use memory backend via --overlay2=*:memory, then consider applying memory limits to the entire container. OR try using the file backend with self medium and setting up size limits on the host rootfs directory.

[ayushr2]

In gVisor, the overlay can be configured in many scenarios:

• Via --overlay2 flag for rootfs or even bind mounts.
• For specific bind mounts using mount annotations

See

gvisor/runsc/container/container.go

Line 939 in d30c58e

func (c *Container) initGoferConfs(ovlConf config.Overlay2, mountHints *boot.PodMountHints, rootfsHint *boot.RootfsHint) error {

So applying the size limit to every overlay in the sandbox based on --overlay2 flag is incorrect.

[stepancheg]

(deleted wrong comments; let me think)

[stepancheg]

New version where overlay size is passed in GoferMountConf.UpperSize.

[ayushr2]

This is guaranteed to be false right? Since we just initialized upperOpts.GetFilesystemOptions on line 587 above.

[stepancheg]

Yes. I added here so that next time someone will add another option here or above, they won't forget to add a comma. I can revert.

[ayushr2]

For similar reasons as mentioned below, if rootfs is being configured by the rootfs annotations (rootfsHint != nil), then overlaySize should be reset.

Also, I think we should extend the rootfs annotation to include specifying size:

gvisor/runsc/boot/mount_hints.go

Line 230 in d19c3bc

// RootfsHint represents extra information about rootfs that are provided via

Maybe dev.gvisor.spec.rootfs.options which has value like size=.... Later we can extend this to support more tmpfs options if need be.

[stepancheg]

Added the option.

    "annotations": {
        "dev.gvisor.spec.rootfs.type": "bind",
        "dev.gvisor.spec.rootfs.source": "/",
        "dev.gvisor.spec.rootfs.overlay": "memory",
        "dev.gvisor.spec.rootfs.options": "size=1m"
    }

[stepancheg]

Next version ready for review.