Add btrfs specific data to filesystem plugin

Collect data exported by btrfs to /sys/fs/btrfs/<uuid>/ and store it in
[:btrfs] for each btrfs filesystem. The current focus is on allocation
data, grouped by block_group type (data, metadata, system), but could be
easily extended in the future.

N.B. it doesn't currently detect any raid mode besides "single" and
"dup", since the main motivation is analyzing metadata usage.

Signed-off-by: Boris Burkov <boris@bur.io>

2 files changed, 71 insertions, 12 deletions

diff --git a/lib/ohai/plugins/filesystem.rb b/lib/ohai/plugins/filesystem.rb
index e86d0908..f6cb6a2b 100644
--- a/lib/ohai/plugins/filesystem.rb
+++ b/lib/ohai/plugins/filesystem.rb
@@ -271,6 +271,30 @@ Ohai.plugin(:Filesystem) do
     fs
   end
 
+  def collect_btrfs_data(entry)
+    btrfs = Mash.new
+    if entry[:fs_type] == "btrfs" && entry["uuid"]
+      uuid = entry["uuid"]
+      alloc = "/sys/fs/btrfs/#{uuid}/allocation"
+      %w{data metadata system}.each do |bg_type|
+        dir = "#{alloc}/#{bg_type}"
+        %w{single dup}.each do |raid|
+          if file_exist?("#{dir}/#{raid}")
+            btrfs["raid"] = raid
+          end
+        end
+        logger.trace("Plugin Filesystem: reading btrfs allocation files at #{dir}")
+        btrfs["allocation"] ||= Mash.new
+        btrfs["allocation"][bg_type] ||= Mash.new
+        %w{total_bytes bytes_used}.each do |field|
+          bytes = file_read("#{dir}/#{field}").chomp.to_i
+          btrfs["allocation"][bg_type][field] = "#{bytes}"
+        end
+      end
+    end
+    btrfs
+  end
+
   collect_data(:linux) do
     fs = Mash.new
 
@@ -394,6 +418,12 @@ Ohai.plugin(:Filesystem) do
       end
     end
 
+    fs.each do |key, entry|
+      if entry[:fs_type] == "btrfs"
+        fs[key][:btrfs] = collect_btrfs_data(entry)
+      end
+    end
+
     by_pair = fs
     by_device = generate_device_view(fs)
     by_mountpoint = generate_mountpoint_view(fs)
diff --git a/spec/unit/plugins/linux/filesystem_spec.rb b/spec/unit/plugins/linux/filesystem_spec.rb
index d4e47505..1cbbe446 100644
--- a/spec/unit/plugins/linux/filesystem_spec.rb
+++ b/spec/unit/plugins/linux/filesystem_spec.rb
@@ -54,6 +54,30 @@ describe Ohai::System, "Linux filesystem plugin" do
       allow(File).to receive(:exist?).with("/dev/#{name}").and_return(false)
       allow(File).to receive(:exist?).with("/dev/mapper/#{name}").and_return(true)
     end
+
+    BTRFS_ALLOC = {
+      "data" => {
+        "total_bytes" => "10000000000",
+        "bytes_used" => "7000000000",
+      },
+      "metadata" => {
+        "total_bytes" => "2000000000",
+        "bytes_used" => "200000000",
+      },
+      "system" => {
+        "total_bytes" => "100000000",
+        "bytes_used" => "10000",
+      },
+    }.freeze
+
+    btrfs_sysfs_base = "/sys/fs/btrfs/d6efda02-1b73-453c-8c74-7d8dee78fa5e/allocation"
+    %w{data metadata system}.each do |bg_type|
+      allow(File).to receive(:exist?).with("#{btrfs_sysfs_base}/#{bg_type}/single").and_return(true)
+      allow(File).to receive(:exist?).with("#{btrfs_sysfs_base}/#{bg_type}/dup").and_return(false)
+      %w{total_bytes bytes_used}.each do |field|
+        allow(plugin).to receive(:file_read).with("#{btrfs_sysfs_base}/#{bg_type}/#{field}").and_return(BTRFS_ALLOC[bg_type][field])
+      end
+    end
   end
 
   describe "when gathering filesystem usage data from df" do
@@ -141,8 +165,8 @@ describe Ohai::System, "Linux filesystem plugin" do
         udev on /dev type tmpfs (rw,mode=0755)
         tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
         devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
-        /dev/mapper/sys.vg-home.lv on /home type xfs (rw,noatime)
-        /dev/mapper/sys.vg-special.lv on /special type xfs (ro,noatime)
+        /dev/mapper/sys.vg-home.lv on /home type btrfs (rw,noatime)
+        /dev/mapper/sys.vg-special.lv on /special type btrfs (ro,noatime)
         /dev/mapper/sys.vg-tmp.lv on /tmp type ext4 (rw,noatime)
         /dev/mapper/sys.vg-usr.lv on /usr type ext4 (rw,noatime)
         /dev/mapper/sys.vg-var.lv on /var type ext4 (rw,noatime)
@@ -165,7 +189,7 @@ describe Ohai::System, "Linux filesystem plugin" do
 
     it "sets fs_type to value from mount" do
       plugin.run
-      expect(plugin[:filesystem]["by_pair"]["/dev/mapper/sys.vg-special.lv,/special"][:fs_type]).to eq("xfs")
+      expect(plugin[:filesystem]["by_pair"]["/dev/mapper/sys.vg-special.lv,/special"][:fs_type]).to eq("btrfs")
     end
 
     it "sets mount_options to an array of values from mount" do
@@ -215,7 +239,7 @@ describe Ohai::System, "Linux filesystem plugin" do
         /dev/mapper/sys.vg-tmp.lv: LABEL=\"/tmp\" UUID=\"74cf7eb9-428f-479e-9a4a-9943401e81e5\" TYPE=\"ext4\"
         /dev/mapper/sys.vg-usr.lv: LABEL=\"/usr\" UUID=\"26ec33c5-d00b-4f88-a550-492def013bbc\" TYPE=\"ext4\"
         /dev/mapper/sys.vg-var.lv: LABEL=\"/var\" UUID=\"6b559c35-7847-4ae2-b512-c99012d3f5b3\" TYPE=\"ext4\"
-        /dev/mapper/sys.vg-home.lv: LABEL=\"/home\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" TYPE=\"xfs\"
+        /dev/mapper/sys.vg-home.lv: LABEL=\"/home\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" TYPE=\"btrfs\"
       BLKID_TYPE
       allow(plugin).to receive(:shell_out).with("/sbin/blkid", timeout: 60).and_return(mock_shell_out(0, @stdout, ""))
     end
@@ -230,6 +254,11 @@ describe Ohai::System, "Linux filesystem plugin" do
       expect(plugin[:filesystem]["by_pair"]["/dev/sda2,"][:uuid]).to eq("e36d933e-e5b9-cfe5-6845-1f84d0f7fbfa")
       expect(plugin[:filesystem]["by_pair"]["/dev/md0,/boot"][:label]).to eq("/boot")
     end
+
+    it "collects btrfs data by uuid" do
+      plugin.run
+      expect(plugin[:filesystem]["by_mountpoint"]["/home"][:btrfs]["allocation"]).to eq(BTRFS_ALLOC)
+    end
   end
 
   describe "when gathering filesystem type data from lsblk" do
@@ -273,7 +302,7 @@ describe Ohai::System, "Linux filesystem plugin" do
         NAME=\"sys.vg-tmp.lv\" UUID=\"74cf7eb9-428f-479e-9a4a-9943401e81e5\" LABEL=\"/tmp\" FSTYPE=\"ext4\"
         NAME=\"sys.vg-usr.lv\" UUID=\"26ec33c5-d00b-4f88-a550-492def013bbc\" LABEL=\"/usr\" FSTYPE=\"ext4\"
         NAME=\"sys.vg-var.lv\" UUID=\"6b559c35-7847-4ae2-b512-c99012d3f5b3\" LABEL=\"/var\" FSTYPE=\"ext4\"
-        NAME=\"sys.vg-home.lv\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" LABEL=\"/home\" FSTYPE=\"xfs\"
+        NAME=\"sys.vg-home.lv\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" LABEL=\"/home\" FSTYPE=\"btrfs\"
         NAME=\"debian--7-root (dm-0)\" UUID=\"09187faa-3512-4505-81af-7e86d2ccb99a\" LABEL=\"root\" FSTYPE=\"ext4\"
       BLKID_TYPE
       allow(plugin).to receive(:shell_out)
@@ -340,7 +369,7 @@ describe Ohai::System, "Linux filesystem plugin" do
         NAME=\"sys.vg-tmp.lv\" UUID=\"74cf7eb9-428f-479e-9a4a-9943401e81e5\" LABEL=\"/tmp\" FSTYPE=\"ext4\"
         NAME=\"sys.vg-usr.lv\" UUID=\"26ec33c5-d00b-4f88-a550-492def013bbc\" LABEL=\"/usr\"
         NAME=\"sys.vg-var.lv\" UUID=\"6b559c35-7847-4ae2-b512-c99012d3f5b3\" LABEL=\"/var\" FSTYPE=\"ext4\"
-        NAME=\"sys.vg-home.lv\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" LABEL=\"/BADhome\" FSTYPE=\"xfs\"
+        NAME=\"sys.vg-home.lv\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" LABEL=\"/BADhome\" FSTYPE=\"btrfs\"
         NAME=\"debian--7-root (dm-0)\" UUID=\"09187faa-3512-4505-81af-7e86d2ccb99a\" LABEL=\"root\" FSTYPE=\"ext4\"
       BLKID_TYPE
       allow(plugin).to receive(:shell_out)
@@ -358,7 +387,7 @@ describe Ohai::System, "Linux filesystem plugin" do
         /dev/mapper/sys.vg-tmp.lv: LABEL=\"/tmp\" UUID=\"74cf7eb9-428f-479e-9a4a-9943401e81e5\" TYPE=\"ext4\"
         /dev/mapper/sys.vg-usr.lv: LABEL=\"/usr\" UUID=\"26ec33c5-d00b-4f88-a550-492def013bbc\" TYPE=\"ext4\"
         /dev/mapper/sys.vg-var.lv: LABEL=\"/var\" UUID=\"6b559c35-7847-4ae2-b512-c99012d3f5b3\" TYPE=\"ext4\"
-        /dev/mapper/sys.vg-home.lv: LABEL=\"/home\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" TYPE=\"xfs\"
+        /dev/mapper/sys.vg-home.lv: LABEL=\"/home\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" TYPE=\"btrfs\"
       BLKID_TYPE
       allow(plugin).to receive(:shell_out).with("/sbin/blkid", timeout: 60).and_return(mock_shell_out(0, @stdout, ""))
     end
@@ -398,8 +427,8 @@ describe Ohai::System, "Linux filesystem plugin" do
         /dev/mapper/sys.vg-root.lv / ext4 rw,noatime,errors=remount-ro,barrier=1,data=ordered 0 0
         tmpfs /lib/init/rw tmpfs rw,nosuid,relatime,mode=755 0 0
         tmpfs /dev/shm tmpfs rw,nosuid,nodev,relatime 0 0
-        /dev/mapper/sys.vg-home.lv /home xfs rw,noatime,attr2,noquota 0 0
-        /dev/mapper/sys.vg-special.lv /special xfs ro,noatime,attr2,noquota 0 0
+        /dev/mapper/sys.vg-home.lv /home btrfs rw,noatime,attr2,noquota 0 0
+        /dev/mapper/sys.vg-special.lv /special btrfs ro,noatime,attr2,noquota 0 0
         /dev/mapper/sys.vg-tmp.lv /tmp ext4 rw,noatime,barrier=1,data=ordered 0 0
         /dev/mapper/sys.vg-usr.lv /usr ext4 rw,noatime,barrier=1,data=ordered 0 0
         /dev/mapper/sys.vg-var.lv /var ext4 rw,noatime,barrier=1,data=ordered 0 0
@@ -425,7 +454,7 @@ describe Ohai::System, "Linux filesystem plugin" do
 
     it "sets fs_type to value from /proc/mounts" do
       plugin.run
-      expect(plugin[:filesystem]["by_pair"]["/dev/mapper/sys.vg-special.lv,/special"][:fs_type]).to eq("xfs")
+      expect(plugin[:filesystem]["by_pair"]["/dev/mapper/sys.vg-special.lv,/special"][:fs_type]).to eq("btrfs")
     end
 
     it "sets mount_options to an array of values from /proc/mounts" do
@@ -469,7 +498,7 @@ describe Ohai::System, "Linux filesystem plugin" do
       allow(plugin).to receive(:which).with("blkid").and_return(nil)
       @stdout = <<~BLKID_TYPE
         NAME=\"/dev/mapper/sys.vg-root.lv\" UUID=\"7742d14b-80a3-4e97-9a32-478be9ea9aea\" LABEL=\"/\" FSTYPE=\"ext4\"
-        NAME=\"/dev/mapper/sys.vg-home.lv\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" LABEL=\"/home\" FSTYPE=\"xfs\"
+        NAME=\"/dev/mapper/sys.vg-home.lv\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" LABEL=\"/home\" FSTYPE=\"btrfs\"
       BLKID_TYPE
       allow(plugin).to receive(:shell_out)
         .with("/sbin/lsblk -n -P -o NAME,UUID,LABEL,FSTYPE", timeout: 60)
@@ -516,7 +545,7 @@ describe Ohai::System, "Linux filesystem plugin" do
         NAME=\"/dev/mapper/sys.vg-root.lv\" UUID=\"7742d14b-80a3-4e97-9a32-478be9ea9aea\" LABEL=\"/\" FSTYPE=\"ext4\"
         NAME=\"/dev/sdb1\" UUID=\"6b559c35-7847-4ae2-b512-c99012d3f5b3\" LABEL=\"/mnt\" FSTYPE=\"ext4\"
         NAME=\"/dev/sdc1\" UUID=\"7f1e51bf-3608-4351-b7cd-379e39cff36a\" LABEL=\"/mnt\" FSTYPE=\"ext4\"
-        NAME=\"/dev/mapper/sys.vg-home.lv\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" LABEL=\"/home\" FSTYPE=\"xfs\"
+        NAME=\"/dev/mapper/sys.vg-home.lv\" UUID=\"d6efda02-1b73-453c-8c74-7d8dee78fa5e\" LABEL=\"/home\" FSTYPE=\"btrfs\"
       BLKID_TYPE
       allow(plugin).to receive(:shell_out)
         .with("/sbin/lsblk -n -P -o NAME,UUID,LABEL,FSTYPE", timeout: 60)