Fix btrfs device stats always being zero (#2516)

* Respect rootfs path config option in btrfs ioctl
* Fix btrfs device stats always being zero

Signed-off-by: Marcus Cobden <leth@users.noreply.github.com>

collector/btrfs_linux.go

@@ -123,13 +123,15 @@ func (c *btrfsCollector) getIoctlStats() (map[string]*btrfsIoctlFsStats, error)
 			continue
 		}
 
-		fs, err := dennwc.Open(mount.mountPoint, true)
+		mountPath := rootfsFilePath(mount.mountPoint)
+
+		fs, err := dennwc.Open(mountPath, true)
 		if err != nil {
 			// Failed to open this mount point, maybe we didn't have permission
 			// maybe we'll find another mount point for this FS later.
 			level.Debug(c.logger).Log(
 				"msg", "Error inspecting btrfs mountpoint",
-				"mountPoint", mount.mountPoint,
+				"mountPoint", mountPath,
 				"err", err)
 			continue
 		}
@@ -140,7 +142,7 @@ func (c *btrfsCollector) getIoctlStats() (map[string]*btrfsIoctlFsStats, error)
 			// perhaps it'll work with a different mount point
 			level.Debug(c.logger).Log(
 				"msg", "Error querying btrfs filesystem",
-				"mountPoint", mount.mountPoint,
+				"mountPoint", mountPath,
 				"err", err)
 			continue
 		}
@@ -155,7 +157,7 @@ func (c *btrfsCollector) getIoctlStats() (map[string]*btrfsIoctlFsStats, error)
 		if err != nil {
 			level.Debug(c.logger).Log(
 				"msg", "Error querying btrfs device stats",
-				"mountPoint", mount.mountPoint,
+				"mountPoint", mountPath,
 				"err", err)
 			continue
 		}

go.mod

@@ -5,7 +5,7 @@ go 1.17
 require (
 	github.com/beevik/ntp v0.3.0
 	github.com/coreos/go-systemd/v22 v22.4.0
-	github.com/dennwc/btrfs v0.0.0-20220403080356-b3db0b2dedac
+	github.com/dennwc/btrfs v0.0.0-20221026161108-3097362dc072
 	github.com/ema/qdisc v0.0.0-20200603082823-62d0308e3e00
 	github.com/go-kit/log v0.2.1
 	github.com/godbus/dbus/v5 v5.1.0

go.sum

@@ -99,8 +99,8 @@ github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ3
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/dennwc/btrfs v0.0.0-20220403080356-b3db0b2dedac h1:cjfIEKdg/lZ+ewJk8FYoYZTN2HY/okVSPtmHLaYMAvE=
-github.com/dennwc/btrfs v0.0.0-20220403080356-b3db0b2dedac/go.mod h1:MYsOV9Dgsec3FFSOjywi0QK5r6TeBbdWxdrMGtiYXHA=
+github.com/dennwc/btrfs v0.0.0-20221026161108-3097362dc072 h1:7jWBDCngQSBfRmrRCpYH3iPPVOe5i8xbl+5rQHkwZDE=
+github.com/dennwc/btrfs v0.0.0-20221026161108-3097362dc072/go.mod h1:MYsOV9Dgsec3FFSOjywi0QK5r6TeBbdWxdrMGtiYXHA=
 github.com/dennwc/ioctl v1.0.0 h1:DsWAAjIxRqNcLn9x6mwfuf2pet3iB7aK90K4tF16rLg=
 github.com/dennwc/ioctl v1.0.0/go.mod h1:ellh2YB5ldny99SBU/VX7Nq0xiZbHphf1DrtHxxjMk0=
 github.com/ema/qdisc v0.0.0-20200603082823-62d0308e3e00 h1:0GHzegkDz/zSrt+Zph1OueNImPdUxoToypnkhhRYTjI=