[PATCH v3 1/3] common/atomicwrites: add helper for multi block atomic writes

[Catherine Hoang <catherine.hoang@oracle.com>]

Add a helper to check that we can perform multi block atomic writes.

Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
---
 common/atomicwrites | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/common/atomicwrites b/common/atomicwrites
index 391bb6f6..88f49a1a 100644
--- a/common/atomicwrites
+++ b/common/atomicwrites
@@ -24,6 +24,27 @@ _get_atomic_write_segments_max()
         grep -w atomic_write_segments_max | grep -o '[0-9]\+'
 }
 
+_require_scratch_write_atomic_multi_fsblock()
+{
+    _require_scratch
+
+    _scratch_mkfs > /dev/null 2>&1 || \
+        _notrun "cannot format scratch device for atomic write checks"
+    _try_scratch_mount || \
+        _notrun "cannot mount scratch device for atomic write checks"
+
+    local testfile=$SCRATCH_MNT/testfile
+    touch $testfile
+
+    local bsize=$(_get_file_block_size $SCRATCH_MNT)
+    local awu_max_fs=$(_get_atomic_write_unit_max $testfile)
+
+    _scratch_unmount
+
+    test $awu_max_fs -ge $((bsize * 2)) || \
+        _notrun "multi-block atomic writes not supported by this filesystem"
+}
+
 _require_scratch_write_atomic()
 {
 	_require_scratch
-- 
2.34.1