On Tue, Mar 23, 2010 at 03:20:10PM -0400, Doug Ledford wrote:
On 03/19/2010 03:01 AM, Luca Berra wrote:
On Thu, Mar 18, 2010 at 10:13:06PM -0400, Doug Ledford wrote:
Second: mdadm-3.1.2-mapfile.patch
Problem: Neil's support for putting the mdadm map file wherever you need
it is nice, but one place in particular needs a special case.
Specifically, mdadm already creates /dev/md if needed to store symlinks,
or in the case of mdmon needing to create pid/sock files (if ALT_RUN is
why on earth do you want to set ALT_RUN=/dev/md ?
Because on Fedora /lib/init/rw doesn't exist, and neither does any other
early rw area other than /dev, and it's too late to create a new one, so
Neither in Mandriva for that matter.
I need to use someplace in /dev. However, I agree with Neil that if you
are hiding things under . names then you are admitting something isn't
right. So, I'm perfectly happy putting the map file in /dev/md as I
think it has a perfect right to exist there.
besides the fact that it is perfectly clear that something is wrong, i
am not vehemently opposing that.
it is messy enough as it is, let's keep assuming /dev/md contains only
array device files.
I don't know how many arrays you have on your system, but I would hardly
call /dev/md messy.
I did not mean /dev/md is messy, I meant the code for locating the map
file is messy, and the code for handling the mdmon pid and socket is
messy....
for that matter on my test rig i have quite a few file in there
/dev/md/imsm0
/dev/md/Volume0
/dev/md/Volume0p1
....
/dev/md/Volume1
/dev/md/Volume1p1
...
besides that you will discover that the only way to make mdmon work is
setting VAR_RUN and ALT_RUN to the same value,
[ citation needed ]
two issues:
1) see the thread on this ml starting with:
[mdadm PATCH 5/9] mdmon: mdmon_pid should return pid from either dir
in practice mdadm looks for the mdmon pid and socket in VAR_RUN, but
until takeover the pid and socket are in ALT_RUN, this means you cannot
do array maintainance until /var is mounted rw.
(been there, done that, had to mount a tmpfs on /var and mount --bind
/dev/.mdadm /var/run/mdadm to fix the array)
Neil refused that patch, but allowed redefinition of VAR_RUN, and i did
not insist.
2) having to keep /var/run mounted during shutdown is a PITA, and iirc
you (redhat) were opposed to having mdmon files in /var/run/mdadm, last
time the issue was discussed here.
something we can
guarantee to be writable even in the direst situation, and i'd keep
/dev/.mdadm
There is no guarantee /dev/.mdadm exists on a clean install, where as I
have made sure that all possible places that might need /dev/md will
create it if it doesn't exist. Hence, the direst of situations is
handled better with /dev/md than with /dev/.mdadm
yes, in mdmon.c ALT_RUN is created before usage, in mapfile.c it is not,
adding an mkdir there would be useful, independent of what we set
ALT_RUN to.
Fourth: mdadm-3.1.2-mapname.patch
Feature: If we are able to easily select the location of the mapfile via
the use of ALT_RUN at compile time, it makes sense to also be able to
this "hunt the mapfile" thing is already ugly as it is, why do we need
an ALT_MAPNAME?
Because /dev/md/map is too easy a name to conflict with a legitimate md
array device name, and that's what it defaults to if you set ALT_RUN to
/dev/md.
if there was any value (except for allowing to set
ALT_RUN to /dev/md) to having the mapfile named differently, just force
it to be called mdadm.map everywere (or incremental.map so the name
reflects the need for the file existance)
Except I set it to md-device-map. Aside from not conflicting with md
device names, the map file name is mostly irrelevant except to indicate
to people perusing the directory what the file is for as nothing uses it
besides mdadm and mdadm will gladly use it with whatever name you call
it as it both creates and uses the file from the same compile time
configuration setting.
I know all this, what i meant is:
why do you feel there is a need for ALT_MAPNAME, would not it be easier
to just define a MAPFILE_NAME with a fixed path and avoid the open_map
juggling in mapfile.c, there is no need for that code, since, as you
state: "mdadm both creates and uses the file from the same compile time
configuration setting."
L.
--
Luca Berra -- bluca@xxxxxxxxxx
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