Adds journal option to container volume create. (#1412)

- Closes #1411.
- Default behavior doesn't change today - with no `journal` option, no
journal gets created.

docs/command-reference.md

@@ -820,7 +820,32 @@ container volume create [--label <label> ...] [--opt <opt> ...] [-s <s>] [--debu
 
 *   `--label <label>`: Set metadata for a volume
 *   `--opt <opt>`: Set driver specific options
-*   `-s <s>`: Size of the volume in bytes, with optional K, M, G, T, or P suffix
+*   `-s <s>`: Size of the volume in bytes, with optional K, M, G, T, or P suffix. Takes precedence over `--opt size=` if both are specified.
+
+**Driver Options**
+
+Driver options are passed with `--opt key=value`. The following options are supported for the default `local` driver:
+
+*   `size=<value>`: Volume size with optional unit suffix (K, M, G, T, P). Minimum 1 MiB. Equivalent to `-s`; if `-s` is also specified, `-s` takes precedence.
+*   `journal=<mode>[:<size>]`: Configure ext4 journaling on the volume. `<mode>` must be one of:
+    *   `ordered` — journals metadata only; data is written to disk before its metadata is committed (default kernel behavior, good balance of safety and performance)
+    *   `writeback` — journals metadata only; data ordering relative to metadata commits is not guaranteed (fastest, least safe)
+    *   `journal` — journals both metadata and data (safest, highest write amplification)
+
+    An optional `:<size>` suffix sets the journal size (same unit suffixes as `size`). If omitted, the kernel selects a default journal size.
+
+**Examples**
+
+```bash
+# create a volume with ordered journaling
+container volume create --opt journal=ordered myvolume
+
+# create a volume with writeback journaling and a 64 MiB journal
+container volume create --opt journal=writeback:64m myvolume
+
+# create a volume with full data journaling and an explicit volume size
+container volume create --opt journal=journal --opt size=10g myvolume
+```
 
 **Anonymous Volumes**