On Sun, Sep 01, 2013 at 02:10:11PM -0400, Zachary Palmer wrote:
> Hello there. I'm not sure if this is the appropriate venue, so
> please let me know if this information should be somewhere else. I
> have configured a Debian 7.0 installation on a Dell Inspiron 17R SE
> laptop to use a bcache root device. The previous known working
> configuration for the laptop was:
>
> /dev/sda (1TB HDD)
> ...
> /dev/sda7 (used as LUKS encrypted volume)
> /dev/mapper/sda7_crypt (used as LVM PV)
> /dev/vg0/home
> /dev/vg0/root
> ...
> /dev/sda8 (used as ext3 /boot)
>
> The new configuration is
>
> /dev/sda (1TB HDD)
> ...
> /dev/sda7 (used as bcache backing device)
> /dev/bcache0 (used as LUKS encrypted volume)
> /dev/mapper/bcache_crypt (used as LVM PV)
> /dev/vg0/home
> /dev/vg0/root
> ...
> /dev/sda8 (used as ext3 /boot)
> /dev/sdb (32GB SSD)
> ...
> /dev/sdb3 (used as bcache caching device)
>
> In order to get things booting, I also:
>
> * Installed a Linux 3.10 kernel from wheezy-backports
> (3.10-0.bpo.2-686-pae)
> * Obtained a copy of the bcache-tools source from the git repo
> and compiled it
> * Constructed a Debian package for bcache-tools using checkinstall
> * Because udev recognition wasn't enough at boot time, added a
> script /etc/initramfs-tools/scripts/init-premount/z-bcache which
> looks like this:
> #!/bin/sh -e
>
> # ZEP - Added (2013-08-29) because some bcache devices
> were not being detected
> # at startup by udev. This sloppy hack should do
> the job.
>
> PREREQS=""
>
> prereqs() { echo "$PREREQS"; }
>
> case "$1" in
> prereqs)
> prereqs
> exit 0
> ;;
> esac
>
> . /scripts/functions
>
> if [ -e '/sys/fs/bcache/register_quiet' ]; then
> log_begin_msg "Scanning for bcache devices..."
> for d in `ls /dev/sd*`; do
> echo "$d" > /sys/fs/bcache/register_quiet
> 2>/dev/null || true
> done
> log_end_msg "bcache device scan complete"
> else
> log_warning_msg "/sys/fs/bcache/register_quiet not
> found; not registering devices"
> fi
> * Executed update-initramfs -u -k all to get everything working
>
> My machine boots from /dev/sda8 and the initramfs has enough
> machinery to get the root drive mounted. I was thrilled until I
> discovered that neither suspend nor hibernate seems to work; the
> suspend process seizes up while suspending devices and never comes
> back. I booted the laptop from a custom Debian live disk using the
> same kernel (3.10-0.bpo.2-686-pae) and performed a series of tests:
>
> * When the bcache kernel module was not loaded, suspend to RAM
> worked correctly.
> * When the bcache kernel module was loaded but no devices were
> registered, suspend to RAM worked correctly.
> * When a single bcache device was registered using "echo
> /dev/sda7 > /sys/fs/bcache/register; echo /dev/sdb3 >
> /sys/fs/bcache/register", suspend to RAM failed to change the power
> state of the machine.
> * With a /dev/bcache0 device in use as an encrypted volume,
> running "echo freezer > /sys/power/pm_test; echo platform >
> /sys/power/disk; echo disk > /sys/power/state" allows the machine to
> awaken from the test correctly.
> * With a /dev/bcache0 device in use as an encrypted volume,
> running "echo devices > /sys/power/pm_test; echo platform >
> /sys/power/disk; echo disk > /sys/power/state" causes the machine to
> hang.
>
> Has suspend/hibernate been tested with bcache? Is it supported? I'm
> trying to figure out if it's my specific laptop hardware causing the
> issue or if bcache is somehow at fault. (Clearly, I can get
> suspend/hibernate back if I migrate back to using just my HDD, but
> caching blocks in a fashion designed for SSDs seems like such a
> lovely idea.)
Suspend/resume works fine for me (sort of). On 3.10.5 I saw some sort of bug
with the freezer that went away if I disabled the Intel MEI driver (or just
applied Kent's for-3.11 branch). I don't recall if Kent ever submitted it for
3.10.
--D
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