From 755798b9331854b850ea0231b3991421abcc5aee Mon Sep 17 00:00:00 2001 From: Richard Yao Date: Sun, 9 Jun 2013 09:13:58 -0400 Subject: [PATCH] Workaround busybox modprobe's inability to load ZFS modules Commit 3a054014e880e5b1ff28e3d87767c45a073da6b5 replaced our modprobe with busybox's modprobe. Unfortunately, busybox's modprobe appears to be unable to properly load modules with more than 1 level of dependencies. The zfs and zpool commands will invoke modprobe if /dev/zvol is missing, which concealed this problem. However, this caused problems because some invocations would fail and under certain circumstances, init would be killed, causing a kernel panic. This issue was made clear by commit c812c35100771bb527f6b03853fa6d8ef66a48fe, which ensured that the zpool and zfs commands were not run until the ZFS module was loaded. busybox modprobe's failure to load module dependencies correctly appears to occur because busybox modprobe does not wait until until a module is loaded before loading a module that depends on it, which is a race. It would be best to correct this race by waiting until the module has properly loaded, but it is not clear that the race is the only thing going wrong and developer time is a premium. We implement a workaround by modifying the busy loop added in the previous commit to explicit call `modprobe zfs` on each iteration. While the first few calls fail due to bugs in busybox modprobe, it will eventually work, after which each call is a noop. This lets us keep looping until either the loop exit condition that /dev/zvol exist is reached or the 5 second timeout is reached. Once the busybox modprobe issue is fixed, this workaround should be safe to revert. Signed-off-by: Richard Yao --- defaults/initrd.scripts | 5 +++-- defaults/linuxrc | 2 -- 2 files changed, 3 insertions(+), 4 deletions(-) diff --git a/defaults/initrd.scripts b/defaults/initrd.scripts index d78ecfe..7e51f0d 100644 --- a/defaults/initrd.scripts +++ b/defaults/initrd.scripts @@ -830,9 +830,10 @@ choose_keymap() { } # This helper function is to be called using call_func_timeout. -# It enables us to wait a reasonable amount of time until /dev/zfs appears. +# This works around the inability of busybox modprobe to handle complex module dependencies. +# This also enables us to wait a reasonable amount of time until /dev/zfs appears. waitForZFS() { - while [ ! -c /dev/zfs ]; do echo >/dev/null; done; + while [ ! -c /dev/zfs ]; do modprobe zfs 2> /dev/null; done; } start_volumes() { diff --git a/defaults/linuxrc b/defaults/linuxrc index 5bc70a3..7b66d52 100644 --- a/defaults/linuxrc +++ b/defaults/linuxrc @@ -299,8 +299,6 @@ then break fi done - - [ "USE_ZFS" = "1" ] && MY_HWOPTS="${MY_HWOPTS} zfs" fi cmdline_hwopts