Modify pool_usage function and callers

Fixes the other part of rockstor#1454.

New behaviour is to return only the used space value, but this now also
includes space reserved by btrfs and unavailable for data.

src/rockstor/fs/btrfs.py

@@ -736,49 +736,24 @@ def shares_usage(pool, share_map, snap_map):
 
 
 def pool_usage(mnt_pt):
-    # @todo: remove temporary raid5/6 custom logic once fi usage
-    # supports raid5/6.
+    """Return used space of the storage pool mounted at mnt_pt.
+
+    Used space is considered to be:
+    - All space currently used by data;
+    - All space currently allocated for metadata and system data.
+    """
     cmd = [BTRFS, 'fi', 'usage', '-b', mnt_pt]
-    total = 0
-    inuse = 0
-    free = 0
-    data_ratio = 1
-    raid56 = False
-    parity = 1
-    disks = set()
     out, err, rc = run_command(cmd)
-    for e in err:
-        e = e.strip()
-        if (re.match('WARNING: RAID56', e) is not None):
-            raid56 = True
-
-    for o in out:
-        o = o.strip()
-        if (raid56 is True and re.match('/dev/', o) is not None):
-            disks.add(o.split()[0])
-        elif (raid56 is True and re.match('Data,RAID', o) is not None):
-            if (o[5:10] == 'RAID6'):
-                parity = 2
-        elif (re.match('Device size:', o) is not None):
-            total = int(o.split()[2]) / 1024
-        elif (re.match('Used:', o) is not None):
-            inuse = int(o.split()[1]) / 1024
-        elif (re.match('Free ', o) is not None):
-            free = int(o.split()[2]) / 1024
-        elif (re.match('Data ratio:', o) is not None):
-            data_ratio = float(o.split()[2])
-            if (data_ratio < 0.01):
-                data_ratio = 0.01
-    if (raid56 is True):
-        num_disks = len(disks)
-        if (num_disks > 0):
-            per_disk = total / num_disks
-            total = (num_disks - parity) * per_disk
-    else:
-        total = total / data_ratio
-        inuse = inuse / data_ratio
-    free = total - inuse
-    return (total, inuse, free)
+
+    used = 0
+    for line in out:
+        fields = re.split('\W+', line)
+        if line.startswith('Data'):
+            used += int(fields[5])
+        elif re.search('Size', line):
+            used += int(fields[3])
+
+    return used / 1024
 
 
 def scrub_start(pool, force=False):

src/rockstor/storageadmin/models/pool.py

@@ -41,21 +41,17 @@ class Pool(models.Model):
 
     @property
     def free(self, *args, **kwargs):
-        #why do we compute pool usage on the fly like this and not like
-        #share usage as part of state refresh? This is a lot simpler and
-        #less code. For share usage, this type of logic could slow things
-        #down quite a bit because there can be 100's of Shares, but number
-        #of Pools even on a large instance is usually no more than a few.
-        try:
-            return pool_usage('%s%s' % (settings.MNT_PT, self.name))[2]
-        except:
-            return self.size
+        # Why do we compute pool usage on the fly like this and not like
+        # share usage as part of state refresh? This is a lot simpler and
+        # less code. For share usage, this type of logic could slow things
+        # down quite a bit because there can be 100's of Shares, but number
+        # of Pools even on a large instance is usually no more than a few.
+        return self.size - pool_usage('%s%s' % (settings.MNT_PT, self.name))
 
     @property
     def reclaimable(self, *args, **kwargs):
         return 0
 
-    @property
     def usage_bound(self, disk_sizes=[], num_devices=0):
         """Return the total amount of storage possible within this pool's set
         of disks, in bytes.
@@ -64,7 +60,7 @@ def usage_bound(self, disk_sizes=[], num_devices=0):
         http://carfax.org.uk/btrfs-usage/js/btrfs-usage.js
         """
         if not disk_sizes:
-            disk_sizes = [int(size) * 1024 for size in self.disk_set
+            disk_sizes = [int(size) for size in self.disk_set
                           .values_list('size', flat=True)
                           .order_by('-size')]
             num_devices = len(disk_sizes)

src/rockstor/storageadmin/views/command.py

@@ -67,7 +67,7 @@ def _refresh_pool_state():
                 pool_info = get_pool_info(fd.name)
                 p.name = pool_info['label']
                 p.raid = pool_raid('%s%s' % (settings.MNT_PT, p.name))['data']
-                p.size = pool_usage('%s%s' % (settings.MNT_PT, p.name))[0]
+                p.size = p.usage_bound()
                 p.save()
             except Exception, e:
                 logger.error('Exception while refreshing state for '

src/rockstor/storageadmin/views/disk.py

@@ -213,7 +213,7 @@ def _update_disk_state():
                 # update disk db object to reflect special root pool status
                 dob.pool = p
                 dob.save()
-                p.size = pool_usage(mount_root(p))[0]
+                p.size = p.usage_bound()
                 enable_quota(p)
                 p.uuid = btrfs_uuid(dob.name)
                 p.save()
@@ -379,7 +379,7 @@ def _btrfs_disk_import(self, dname, request):
                 do.save()
                 mount_root(po)
             po.raid = pool_raid('%s%s' % (settings.MNT_PT, po.name))['data']
-            po.size = pool_usage('%s%s' % (settings.MNT_PT, po.name))[0]
+            po.size = p.usage_bound()
             po.save()
             enable_quota(po)
             import_shares(po, request)

src/rockstor/storageadmin/views/pool.py

@@ -273,7 +273,7 @@ def post(self, request):
                 d.pool = p
                 d.save()
             add_pool(p, dnames)
-            p.size = pool_usage(mount_root(p))[0]
+            p.size = p.usage_bound()
             p.uuid = btrfs_uuid(dnames[0])
             p.save()
             return Response(PoolInfoSerializer(p).data)
@@ -416,11 +416,11 @@ def put(self, request, pname, command):
                 size_cut = 0
                 for d in disks:
                     size_cut += d.size
-                if (size_cut >= usage[2]):
+                if (size_cut >= usage):
                     e_msg = ('Removing these(%s) disks may shrink the pool by '
                              '%dKB, which is greater than available free space'
                              ' %dKB. This is not supported.' %
-                             (dnames, size_cut, usage[2]))
+                             (dnames, size_cut, usage))
                     handle_exception(Exception(e_msg), request)
 
                 resize_pool(pool, dnames, add=False)
@@ -435,8 +435,7 @@ def put(self, request, pname, command):
             else:
                 e_msg = ('command(%s) is not supported.' % command)
                 handle_exception(Exception(e_msg), request)
-            usage = pool_usage('/%s/%s' % (settings.MNT_PT, pool.name))
-            pool.size = usage[0]
+            pool.size = pool.usage_bound()
             pool.save()
             return Response(PoolInfoSerializer(pool).data)