The new snapdev dataset property may be set to control the
visibility of zvol snapshot devices. By default this value
is set to 'hidden' which will prevent zvol snapshots from
appearing under /dev/zvol/ and /dev/<dataset>/. When set to
'visible' all zvol snapshots for the dataset will be visible.
This functionality was largely added because when automatic
snapshoting is enabled large numbers of read-only zvol snapshots
will be created. When creating these devices the kernel will
attempt to read their partition tables, and blkid will attempt
to identify any filesystems on those partitions. This leads
to a variety of issues:
1) The zvol partition tables will be read in the context of
the `modprobe zfs` for automatically imported pools. This
is undesirable and should be done asynchronously, but for
now reducing the number of visible devices helps.
2) Udev expects to be able to complete its work for a new
block devices fairly quickly. When many zvol devices are
added at the same time this is no longer be true. It can
lead to udev timeouts and missing /dev/zvol links.
3) Simply having lots of devices in /dev/ can be aukward from
a management standpoint. Hidding the devices your unlikely
to ever use helps with this. Any snapshot device which is
needed can be made visible by changing the snapdev property.
NOTE: This patch changes the default behavior for zvols which
was effectively 'snapdev=visible'.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1235Closes#945
Issue #956
Issue #756
During the original ZoL port the vdev_uses_zvols() function was
disabled until it could be properly implemented. This prevented
a zpool from use a zvol for its slog device.
This patch implements that missing functionality by adding a
zvol_is_zvol() function to zvol.c. Given the full path to a
device it will lookup the device and verify its major number
against the registered zvol major number for the system. If
they match we know the device is a zvol.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#1131
For legacy reasons the zvol.c and vdev_disk.c Linux compatibility
code ended up in sys/blkdev.h and sys/vdev_disk.h headers. While
there are worse places for this code to live it should be in a
linux/blkdev_compat.h header. This change moves this block device
Linux compatibility code in to the linux/blkdev_compat.h header
and updates all the correct #include locations. This is not a
functional change or bug fix, it is just code cleanup.
One of the neat tricks an autoconf style project is capable of
is allow configurion/building in a directory other than the
source directory. The major advantage to this is that you can
build the project various different ways while making changes
in a single source tree.
For example, this project is designed to work on various different
Linux distributions each of which work slightly differently. This
means that changes need to verified on each of those supported
distributions perferably before the change is committed to the
public git repo.
Using nfs and custom build directories makes this much easier.
I now have a single source tree in nfs mounted on several different
systems each running a supported distribution. When I make a
change to the source base I suspect may break things I can
concurrently build from the same source on all the systems each
in their own subdirectory.
wget -c http://github.com/downloads/behlendorf/zfs/zfs-x.y.z.tar.gz
tar -xzf zfs-x.y.z.tar.gz
cd zfs-x-y-z
------------------------- run concurrently ----------------------
<ubuntu system> <fedora system> <debian system> <rhel6 system>
mkdir ubuntu mkdir fedora mkdir debian mkdir rhel6
cd ubuntu cd fedora cd debian cd rhel6
../configure ../configure ../configure ../configure
make make make make
make check make check make check make check
This change also moves many of the include headers from individual
incude/sys directories under the modules directory in to a single
top level include directory. This has the advantage of making
the build rules cleaner and logically it makes a bit more sense.
