autodetect: refactor raid device detection

FS#10061 still isn't dead, its just resting:

https://bbs.archlinux.org/viewtopic.php?pid=1056003

An strace from a helpful user shows that our mdadm call is trying to
open a block device and the call never returns:

  open("/dev/sdb", O_RDONLY|O_DIRECT|O_LARGEFILE

Fix this by only scanning explicitly the block devices we're interested
in, found via sysfs. This is an all around win for everyone, especially
users who have mdadm installed without any need for it.

This changes some of our assumptions about the environment:

- the mdadm binary exists when we find md devices in /sys
- the user running mkinitcpio isn't any specific UID or part of any
  particular group, but merely has read access to the block devices
  we're about to scan.

Signed-off-by: Dave Reisner <dreisner@archlinux.org>

1 files changed, 22 insertions, 6 deletions

diff --git a/install/autodetect b/install/autodetect
index 3fb87ce..5cc908c 100644
--- a/install/autodetect
+++ b/install/autodetect
@@ -1,6 +1,9 @@
 #!/bin/bash
 
 build() {
+    local -a md_devs
+    local dev insufficient_perms
+
     MODULE_FILE=$workdir/autodetect_modules
 
     add_if_avail() {
@@ -29,15 +32,28 @@ build() {
         add_if_avail "$usrfstype"
     fi
 
-    if (( UID == 0 )) || in_array 'disk' $(groups); then
-        if [[ -x $(type -P mdadm) ]]; then
-            mdadm -Esv /dev/[hrsv]d* /dev/{ida,cciss,ataraid,mapper}/* |
+    # look for raid devices
+    shopt -s nullglob
+    for dev in /sys/class/block/*/md/dev-*; do
+        dev=/dev/${dev#*/dev-}
+
+        [[ -r $dev ]] || insufficient_perms=1
+
+        md_devs+=("$dev")
+    done
+    shopt -u nullglob
+
+    # scan members of raid devices if found
+    if (( ${#md_devs[*]} )); then
+        (( !QUIET )) && plain "found %d raid members to scan" "${#md_devs[*]}"
+        if (( ! insufficient_perms )); then
+            mdadm -Esv "${md_devs[@]}" |
                 sed -n 's/.*level=\([^ ]\+\) .*/\1/p' |
                 sed 's/\<raid[456]\>/raid456/g' | sort -u >>"$MODULE_FILE"
+        else
+            warning "Insufficient permission to perform autodetection for mdadm devices"
+            raid_autodetect_failed=1
         fi
-    else
-        error "Insufficient permission to perform autodetection for mdadm devices"
-        raid_autodetect_failed=1
     fi
 
     if (( !QUIET )) && [[ -s $MODULE_FILE ]]; then