similar to: [PATCH nbdkit] New tmpdisk plugin.

v2 was here: https://www.redhat.com/archives/libguestfs/2020-March/msg00154.html v3: - Micro-optimize tmpdir. - Quote $disk in default command shell fragment. - Don't redirect mkfs output to /dev/null. Instead use exec </dev/null >/dev/null before the shell fragment. We may want to do this in other places where we run external shell scripts, or more generally for all

An evolution of v1 here: https://www.redhat.com/archives/libguestfs/2020-April/msg00035.html I want to generalize the tmpdisk plugin, particularly so you can use commands like ‘qemu-img create’ or even ‘virt-builder’. (Actually virt-builder really works - I tested it - but of course it causes a 30+ second delay when connecting to the server.) You can now use commands such as: nbdkit tmpdisk

This can be used for creating temporary disks to thin clients, as a kind of "remote tmpfs". See also: https://www.redhat.com/archives/libguestfs/2020-March/msg00134.html --- plugins/data/nbdkit-data-plugin.pod | 1 + plugins/file/nbdkit-file-plugin.pod | 1 + plugins/linuxdisk/nbdkit-linuxdisk-plugin.pod | 7 +- plugins/memory/nbdkit-memory-plugin.pod |

v2 was here: https://www.redhat.com/archives/libguestfs/2020-April/msg00075.html In v3: - Add [VAR=VALUE ...] to manual. - Various minor improvements to the manual. - Work (at least, in theory - not tested) with block devices or symlinks. I didn't document this because it's hard to ensure these files or block devices would be cleaned up, so here be dragons. - Remove O_NOCTTY. -

Patch 1/2 is uncontroversial. Patch 2/2 is an interesting idea I had to generalize this plugin. It already uses a complete embedded shell script to do most of the work. What if, instead of making special cases for "type" and "label" params, we simply turn any other plugin parameters into script variables? This part of it works fine. However there is another problem which is

Needs some work still, see in particular the commit message for patch 3. Rich.

Another interesting thing you can do with this plugin: https://rwmj.wordpress.com/2019/02/19/nbdkit-linuxdisk-plugin/ v2: - Fix inconsistent tab/space. - All 3 plugins now contain a block of text pointing to the other 2 plugins. - TMDIR -> TMPDIR - Unlink the temporary file and other cleanups along error paths. - fclose -> pclose, and check the return value for errors. -

Turns out Japanese trains are good for coding! In supermin we have a bunch of code to create the libguestfs appliance. It creates it directly using libext2fs (part of e2fsprogs). We can use the same technique to create ext2 virtual disks in nbdkit, which is what this new plugin does. Why a new plugin instead of modifying the floppy plugin? See the 4/4 commit message for an explanation. The

For v3 I reimplemented this using mke2fs -d. This obviously makes the implementation a whole lot simpler, but cannot support multiple directory merging. Patches 1-3 are the same as before. I've also reproduced the notes from v2 below. v2: - Fix inconsistent tab/space. - All 3 plugins now contain a block of text pointing to the other 2 plugins. - TMDIR -> TMPDIR - Unlink the

For review only, this needs some clean up and more tests. My eyes are going cross-eyed looking at the calculate_offset_of_entry function, so time to take a break ... Rich.

This creates filesystems on demand. A client simply connects with a desired export name and a new export is created. The export is persistent (until deleted by the server admin), and clients may disconnect and reconnect. In some respects this is similar to the nbdkit-tmpdisk-plugin, or nbdkit-file-plugin with the dir= option. --- plugins/ondemand/nbdkit-ondemand-plugin.pod | 190 ++++++

There's a lot of code in nbdkit-file-plugin which it would be nice to reuse elsewhere. One possible approach (as outlined here) is simply to move the file callbacks (like file.pread, file.pwrite, file.zero etc) to a new mini-library. They can then be consumed by other plugins fairly easily by doing: static void * foo_open (int readonly) { struct fileops *fops; int fd, flags; /*

On 3/17/20 3:53 AM, Richard W.M. Jones wrote: > This can be used for creating temporary disks to thin clients, as a > kind of "remote tmpfs". > > See also: > https://www.redhat.com/archives/libguestfs/2020-March/msg00134.html > --- > +++ b/plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod > @@ -0,0 +1,157 @@ > +=head1 NAME > + > +nbdkit-tmpdisk-plugin - create

I like this change. I think we were overloading the config_complete method before to do two different things (complete configuration; do any allocation/housekeeping necessary before we can start serving). The only questions in my mind are whether we want this before 1.18, and whether the name ("get_ready") is a good one. Rich.

For context see these threads: https://lists.gnu.org/archive/html/qemu-discuss/2020-06/threads.html#00053 https://lists.gnu.org/archive/html/qemu-block/2020-06/threads.html#01496 Rich.

This allows us to be much more flexible about what commands can be used. It also means we do not need to encode any special behaviour for type or label parameters. --- plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod | 91 +++++++++----- plugins/tmpdisk/tmpdisk.c | 147 ++++++++++++++-------- plugins/tmpdisk/default-command.sh.in | 6 + 3 files changed, 164 insertions(+), 80

Since v1: - rework .can_cache to be tri-state, with default of no advertisement (ripple effect through other patches) - add a lot more patches in order to round out filter support And in the meantime, Rich pushed NBD_CMD_CACHE support into libnbd, so in theory we now have a way to test cache commands through the entire stack. Eric Blake (24): server: Internal hooks for implementing

Here's changes to the file plugin (which I'm happy with) and a new exportname filter (which is still at RFC stage; I need to finish implementing strict mode in .open, and add tests). I also discovered that we really want .list_exports and .open to know when they are used on plaintext vs. tls clients for --tls=on, and we may want to split out a new .default_export callback rather than

This is the second version to support efficient zero for block devices on older kernels (e.g. RHEL 7.5), and file systems that do not support yet FALLOC_FS_ZERO_RANGE (e.g. NFS 4.2). Changes since v1: - Split to smaller patches - Skip linux only includes on other systems - Skip code using BLKZEROOUT if the macro is not defined - Try BLKZEROOUT only if the offset and count are aligned to device

This allows us to be much more flexible about what commands can be used. It also means we do not need to encode any special behaviour for type or label parameters. --- plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod | 115 ++++++++++---- tests/Makefile.am | 2 + plugins/tmpdisk/tmpdisk.c | 184 ++++++++++++++++------ plugins/tmpdisk/default-command.sh.in |