feat(info): add memAvailable to host info

Expose MemAvailable alongside MemFree/MemTotal in `podman info` host
section, sourced from libpod/define/info.go's MemInfo.

Fixes: #29116 https://github.com/podman-container-tools/podman/issues/29116

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Evzen Gasta <evzen.ml@seznam.cz>

test(info): add coverage for host.memAvailable

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Evzen Gasta <evzen.ml@seznam.cz>

docs/source/markdown/podman-info.1.md

@@ -75,6 +75,7 @@ host:
   kernel: 5.13.13-200.fc34.x86_64
   linkmode: dynamic
   logDriver: journald
+  memAvailable: 14567456768
   memFree: 1833385984
   memTotal: 16401895424
   networkBackend: netavark
@@ -218,6 +219,7 @@ $ podman info --format json
     },
     "kernel": "5.13.13-200.fc34.x86_64",
     "logDriver": "journald",
+    "memAvailable": 14567456768,
     "memFree": 1785753600,
     "memTotal": 16401895424,
     "networkBackend": "netavark",

libpod/define/info.go

@@ -47,6 +47,7 @@ type HostInfo struct {
 	Kernel             string            `json:"kernel"`
 	LogDriver          string            `json:"logDriver"`
 	MemFree            int64             `json:"memFree"`
+	MemAvailable       int64             `json:"memAvailable"`
 	MemTotal           int64             `json:"memTotal"`
 	NetworkBackend     string            `json:"networkBackend"`
 	NetworkBackendInfo types.NetworkInfo `json:"networkBackendInfo"`

libpod/info.go

@@ -122,6 +122,7 @@ func (r *Runtime) hostInfo() (*define.HostInfo, error) {
 		Hostname:              host,
 		Kernel:                kv,
 		MemFree:               mi.MemFree,
+		MemAvailable:          mi.MemAvailable,
 		MemTotal:              mi.MemTotal,
 		NetworkBackend:        r.config.Network.NetworkBackend,
 		NetworkBackendInfo:    r.network.NetworkInfo(),

test/apiv2/45-system.at

@@ -12,7 +12,10 @@ t GET /v1.52/system/df 200 '{"ImageUsage":{},"ContainerUsage":{},"VolumeUsage":{
 t GET libpod/system/df 200 '{"ImagesSize":0,"Images":[],"Containers":[],"Volumes":[]}'
 
 # Create volume. We expect df to report this volume next invocation of system/df
-t GET libpod/info 200
+t GET libpod/info 200 \
+    .host.memTotal~[0-9]\\+ \
+    .host.memFree~[0-9]\\+ \
+    .host.memAvailable~[0-9]\\+
 volumepath=$(jq -r ".store.volumePath" <<<"$output")
 t POST libpod/volumes/create name=foo1  201 \
     .Name=foo1 \

test/e2e/info_test.go

@@ -244,6 +244,21 @@ var _ = Describe("Podman Info", func() {
 		}
 	})
 
+	It("Podman info: check host.memAvailable is sane", func() {
+		session := podmanTest.PodmanExitCleanly("info", "--format", "{{.Host.MemTotal}} {{.Host.MemAvailable}}")
+		var total, avail int64
+		_, err := fmt.Sscanf(session.OutputToString(), "%d %d", &total, &avail)
+		Expect(err).ToNot(HaveOccurred())
+
+		// On Linux, MemAvailable must always be reported; -1 is the
+		// sentinel used on platforms where the kernel doesn't expose
+		// this value.
+		Expect(avail).To(BeNumerically(">=", 0), "MemAvailable is supported (not the -1 'unknown' sentinel)")
+
+		// MemAvailable (reclaimable memory included) can never exceed MemTotal.
+		Expect(avail).To(BeNumerically("<=", total), "MemAvailable does not exceed MemTotal")
+	})
+
 	It("Podman info: check lock count", Serial, func() {
 		// This should not run on architectures and OSes that use the file locks backend.
 		// Which, for now, is Linux + RISCV and FreeBSD, neither of which are in CI - so

test/system/005-info.bats

@@ -44,6 +44,9 @@ host.conmon.path          | $expr_path
 host.conmon.package       | .*conmon.*
 host.cgroupManager        | \\\(systemd\\\|cgroupfs\\\)
 host.cgroupVersion        | v[12]
+host.memFree              | [0-9]\\\+
+host.memAvailable         | [0-9]\\\+
+host.memTotal             | [0-9]\\\+
 host.networkBackendInfo   | .*dns.*package.*
 host.ociRuntime.path      | $expr_path
 host.pasta                | .*executable.*package.*
@@ -62,6 +65,18 @@ store.imageStore.number   | 1
     done < <(parse_table "$tests")
 }
 
+@test "podman info - host.memAvailable is sane" {
+    run_podman info --format '{{.Host.MemTotal}} {{.Host.MemAvailable}}'
+    read -r total avail <<<"$output"
+
+    # On Linux, MemAvailable must always be reported; -1 is the sentinel
+    # used on platforms where the kernel doesn't expose this value.
+    assert "$avail" -ge 0 "MemAvailable is supported (not the -1 'unknown' sentinel)"
+
+    # MemAvailable (reclaimable memory included) can never exceed MemTotal.
+    assert "$avail" -le "$total" "MemAvailable does not exceed MemTotal"
+}
+
 @test "podman info - confirm desired runtime" {
     if [[ -z "$CI_DESIRED_RUNTIME" ]]; then
         # When running in Cirrus, CI_DESIRED_RUNTIME *must* be defined