btrfs-progs: docs: update dev stats help and manual page

Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/Documentation/btrfs-device.asciidoc b/Documentation/btrfs-device.asciidoc
index 193e273..1e3b3a3 100644 (file)
--- a/Documentation/btrfs-device.asciidoc
+++ b/Documentation/btrfs-device.asciidoc
@@ -100,8 +100,9 @@ prior scanning. See the mount option 'device'.
 
 *stats* [-zs] <path>|<device>::
 Read and print the device IO error statistics for all devices of the given
-filesystem identified by <path> or for a single <device>. See section *DEVICE
-STATS* for more information.
+filesystem identified by <path> or for a single <device>. The filesystem must
+be mounted.  See section *DEVICE STATS* for more information about the reported
+statistics and the meaning.
 +
 `Options`
 +

diff --git a/cmds-device.c b/cmds-device.c
index ba0e436..3e053d9 100644 (file)
--- a/cmds-device.c
+++ b/cmds-device.c
@@ -372,8 +372,10 @@ out:
 }
 
 static const char * const cmd_device_stats_usage[] = {
-       "btrfs device stats [-z] <path>|<device>",
-       "Show current device IO stats.",
+       "btrfs device stats [options] <path>|<device>",
+       "Show device IO error statistics",
+       "Show device IO error statistics for all devices of the given filesystem",
+       "identified by PATH or DEVICE. The filesystem must be mounted.",
        "",
        "-z|--reset             show current stats and reset values to zero",
        "-s                     return non-zero if any stat counter is not zero",