mkdumprd: omit dracut modules in case of no dm target

In case of on dm related target, we can clearly and safely
remove many unnecessary modules to reduce initramfs size,
and to enhance stability.

Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>

mkdumprd

@@ -372,16 +372,44 @@ check_crypt()
     return 1
 }
 
+is_dm()
+{
+    if [ -d "/sys/dev/block/$1/dm" ]; then
+        return 0
+    fi
+
+    return 1
+}
+
 crypt_exists=0
 omit_dracut_modules()
 {
+    local target majmin
+    local dm_exists
+
     # Skip fadump case
     is_fadump_capable && return
 
+    dm_exists=0
+
+    for target in $(get_kdump_targets); do
+        if [ -b "$target" ]; then
+            majmin=$(get_maj_min $target)
+            # Check "dm"
+            check_block_and_slaves is_dm $majmin && dm_exists=1
+        fi
+    done
+
     # Omit "crypt", BZ1451717
     if [ "$crypt_exists" == "0" ]; then
         add_dracut_arg "--omit" "crypt"
     fi
+
+    # Further omit more modules in case of no dm related target
+    if [ "$dm_exists" == "0" ]; then
+        # "dm_exists=0" implies "crypt_exists=0"
+        add_dracut_arg "--omit" "lvm dm multipath dmraid"
+    fi
 }
 
 if ! check_resettable; then