Add xattr .totl. tag

Add the .totl. xattr tag.  When the tag is set the end of the name
specifies a total name with 3 encoded u64s separated by dots.  The value
of the xattr is a u64 that is added to the named total.   An ioctl is
added to read the totals.

Signed-off-by: Zach Brown <zab@versity.com>

tests/tests/totl-xattr-tag.sh

@@ -0,0 +1,126 @@
+t_require_commands touch rm setfattr scoutfs find_xattrs
+
+read_xattr_totals()
+{
+	sync
+	scoutfs read-xattr-totals -p "$T_M0"
+}
+
+echo "== single file"
+touch "$T_D0/file-1"
+setfattr -n scoutfs.totl.test.1.2.3 -v 1 "$T_D0/file-1" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test.4.5.6 -v 1 "$T_D0/file-1" 2>&1 | t_filter_fs
+read_xattr_totals
+
+echo "== multiple files add up"
+touch "$T_D0/file-2"
+setfattr -n scoutfs.totl.test.1.2.3 -v 1 "$T_D0/file-2" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test.4.5.6 -v 1 "$T_D0/file-2" 2>&1 | t_filter_fs
+read_xattr_totals
+
+echo "== removing xattr updates total"
+setfattr -x scoutfs.totl.test.4.5.6 "$T_D0/file-2" 2>&1 | t_filter_fs
+read_xattr_totals
+
+echo "== updating xattr updates total"
+setfattr -n scoutfs.totl.test.1.2.3 -v 10 "$T_D0/file-2" 2>&1 | t_filter_fs
+read_xattr_totals
+
+echo "== removing files update total"
+rm -f "$T_D0/file-1"
+read_xattr_totals
+rm -f "$T_D0/file-2"
+read_xattr_totals
+
+echo "== multiple files/names in one transaction"
+for a in $(seq 1 10); do 
+	touch "$T_D0/file-$a"
+	setfattr -n scoutfs.totl.test.1.2.3 -v $a "$T_D0/file-$a" 2>&1 | t_filter_fs
+done
+read_xattr_totals
+rm -rf "$T_D0"/file-[0-9]*
+
+echo "== testing invalid names"
+touch "$T_D0/invalid"
+setfattr -n scoutfs.totl.test... -v 10 "$T_D0/invalid" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test..2.3 -v 10 "$T_D0/invalid" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test.1..3 -v 10 "$T_D0/invalid" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test.1.2. -v 10 "$T_D0/invalid" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test.1 -v 10 "$T_D0/invalid" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test.1.2 -v 10 "$T_D0/invalid" 2>&1 | t_filter_fs
+
+echo "== testing invalid values"
+setfattr -n scoutfs.totl.test.1.2.3 -v "+1" "$T_D0/invalid" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test.1.2.3 -v "10." "$T_D0/invalid" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test.1.2.3 -v "-" "$T_D0/invalid" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test.1.2.3 -v "junk10" "$T_D0/invalid" 2>&1 | t_filter_fs
+setfattr -n scoutfs.totl.test.1.2.3 -v "10junk" "$T_D0/invalid" 2>&1 | t_filter_fs
+rm -f "$T_D0/invalid"
+
+echo "== larger population that could merge"
+NR=5000
+TOTS=100
+CHECK=100
+PER_DIR=1000
+PER_FILE=10
+
+declare -A totals counts
+LOTS="$T_D0/lots"
+
+for i in $(seq 0 $PER_DIR $NR); do
+	p="$LOTS/$((i / PER_DIR))"
+	mkdir -p $p
+done
+for i in $(seq 0 $PER_FILE $NR); do
+	p="$LOTS/$((i / PER_DIR))/file-$((i / PER_FILE))"
+	touch $p
+done
+
+for phase in create update remove; do
+	for i in $(seq 0 $NR); do
+		p="$LOTS/$((i / PER_DIR))/file-$((i / PER_FILE))"
+
+		t=$((i % TOTS))
+		n="scoutfs.totl.test-$i.$t.0.0"
+
+		case $phase in 
+			create)
+				v="$i"
+				setfattr -n "$n" -v "$v" "$p" 2>&1 >> $T_TMP.sfa
+				((totals[$t]+=$v))
+				((counts[$t]++))
+				;;
+			update)
+				v=$((i * 3))
+				delta=$((i * 2))
+				setfattr -n "$n" -v "$v" "$p" 2>&1 >> $T_TMP.sfa
+				((totals[$t]+=$delta))
+				;;
+			remove)
+				v=$((i * 3))
+				setfattr -x "$n" "$p" 2>&1 >> $T_TMP.sfa
+				((totals[$t]-=$v))
+				((counts[$t]--))
+				;;
+		esac
+
+		if [ "$i" -gt 0 -a "$((i % CHECK))" == "0" ]; then
+			echo "checking $phase $i" > $T_TMP.check_arr
+			echo "checking $phase $i" > $T_TMP.check_read
+
+			( for k in ${!totals[@]}; do
+				echo "$k.0.0 = ${totals[$k]}, ${counts[$k]}"
+			  done ) | grep -v "= 0, 0$" | sort -n >> $T_TMP.check_arr
+
+			sync
+			read_xattr_totals | sort -n >> $T_TMP.check_read
+
+			diff -u $T_TMP.check_arr $T_TMP.check_read || \
+				t_fail "totals read didn't match expected arrays"
+		fi
+	done
+done
+
+rm -rf "$T_D0/merging"
+
+t_pass