Add stage-mulit-part test

Add a test which stages a file in multiple parts while a long-lived
process is blocking on offline extents trying to compare the file to the
known contents.

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

tests/sequence

@@ -16,6 +16,7 @@ createmany-parallel.sh
 createmany-large-names.sh
 createmany-rename-large-dir.sh
 stage-release-race-alloc.sh
+stage-multi-part.sh
 basic-posix-consistency.sh
 dirent-consistency.sh
 lock-ex-race-processes.sh

tests/tests/stage-multi-part.sh

@@ -0,0 +1,69 @@
+#
+# Stage a large file in multiple parts and have a reader read it while
+# it's being staged.  This has found problems with extent access
+# locking.
+#
+
+t_require_commands scoutfs perl cmp rm
+
+FILE_BYTES=$((4 * 1024 * 1024 * 1024))
+FILE_BLOCKS=$((FILE_BYTES / 4096))
+FRAG_BYTES=$((128 * 1024 * 1024))
+FRAG_BLOCKS=$((FRAG_BYTES / 4096))
+NR_FRAGS=$((FILE_BLOCKS / FRAG_BLOCKS))
+
+#
+# high bandwidth way to generate file contents with predictable
+# contents.  We use ascii lines with the block identity, padded to 4KB
+# with spaces.
+#
+# $1 is number of 4k blocks to write, and each block gets its block
+# number in the line.  $2, $3, and $4 are fields that are put in every
+# block.
+#
+gen() {
+	perl -e 'for (my $i = 0; $i < '$1'; $i++) { printf("mount %020u process %020u file %020u blkno %020u%s\n", '$2', '$3', '$4', $i, " " x 3987); }'
+}
+
+release_file() {
+        local path="$1"
+        local vers=$(scoutfs stat -s data_version "$path")
+
+        scoutfs release "$path" "$vers" 0 $FILE_BLOCKS
+}
+
+stage_file() {
+        local path="$1"
+        local vers=$(scoutfs stat -s data_version "$path")
+        local off=0
+
+	for a in $(seq 1 $NR_FRAGS); do
+		scoutfs stage "$path" "$vers" $off $FRAG_BYTES \
+			<(gen $FRAG_BLOCKS $a $a $a)
+		((off+=$FRAG_BYTES))
+	done
+}
+
+FILE="$T_D0/file"
+
+whole_file() {
+	for a in $(seq 1 $NR_FRAGS); do
+		gen $FRAG_BLOCKS $a $a $a
+	done
+}
+
+#
+# just one pass through the file.
+#
+
+whole_file > "$FILE"
+release_file "$FILE"
+
+cmp "$FILE" <(whole_file) &
+pid=$!
+
+stage_file "$FILE"
+
+wait $pid || t_fail "comparison failed"
+
+t_pass