[[!meta copyright="Copyright © 2008, 2009 Free Software Foundation, Inc."]] [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable id="license" text="Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled [[GNU Free Documentation License|/fdl]]."]]"""]] Sergiu Ivanov Mail: # Google Summer of Code: 2009 Project **Unionmount**: The goal of this project is to make it possible to set translators in unionmount mode, which means that the filesystem published by the mounted translator will get merged with the directory tree of the node the translator is mounted onto. For documentation, see [[hurd/translator/unionmount]]. At the Final Evaluation, this project was given a passing evaluation by **antrik**. This means that the union-mount functionality is working and has been tested normally to collaborate with `eth-multiplexer`. --- ## Roadmap ### DONE (Dates in brackets show the completion date) * **Make `unionfs` build.** *(24 May)* For reasons unknown to me, `unionfs` Makefile was configured to search for include files from under `$(prefix)/include`, while `$(prefix)` was never defined. Setting `$(prefix)` to `/usr` solved the problem. * **Change the command line parsing in `unionfs` to comply with the requirements of `unionmount`.** *(25 May)* Although the core functionality of `unionmount` heavily relies on `unionfs`, the command line interface of these two programs is completely different: `unionfs` operates on directories, the list of which is explicitly specified, while `unionmount` *always* merges the underlying filesystem and the filesystem published by the mountee. Therefore, options like `--add`, `--remove`, `--underlying` (specific to `unionfs`) make little sense in `unionmount` context. These options have been removed. Also, `unionmount` must be able to pass some switches to the mountee, which means that it should stop parsing the command line arguments immediately after having encountered the path to the mountee (very similar to how `settrans` works). This functionality has also been implemented. * **Make `unionmount` capable of starting the mountee.** *(28 May)* The idea behind implementation of this goal is that `unionmount` should provide a proxy node on which to set the mountee. The main issue about this goal was the fact that the mountee *cannot* be started during the initialization of `unionmount`, because in this phase `unionmount` is not capable of responding to RPCs, while many translators try to `io_stat` their underlying node or do other interesting things on startup. The solution to this problem is, obviously, *lazy* startup, i.e. the mountee is started at the first attempt to access (via `dir_lookup` or `dir_readdir`) the merged filesystem published by `unionmount`. * **Include the filesystem published by the mountee in the list of merged filesystems.** *(1 Jun)* `unionfs` operates on a list of ports to the underlying filesystems, therefore, to finish the unionmount functionality, I had to include the port to the mountee in this list. * **Learn Texinfo.** *(Jun 4)* In order to produce canonical documentation I had to learn the Texinfo documentation format. * **Write documentation for `unionmount`.** *(Jun 5)* The basic unionmount functionality being finished, it has to be documented properly, lest it should lag behind and remain unfinished eventually. * **Write documentation for `unionfs`.** *(Jun 5)* `unionfs` is not exactly well-documented at the moment, the only help being provided by the comments in the sources. The goal is to write a more coherent documentation. * **Start with a clean unionfs and implement the `--mount` argument** *(11 Jun)* It was suggested to implement the union mount functionality first, instead of doing some partial adaptation of `unionfs` to `unionmount` and leaving the complete adaptation for the future. * **Compile GNU/Hurd from source to be able to study eth-multiplexer.** *(16 Jun)* On my way to getting a working instance of eth-multiplexer I learnt how I could compile GNU/Hurd in a Debian GNU/Hurd system. * **Setup the `devnode`--`eth-multiplexer`--`pfinet chain`.** *(30 Jun)* Due to the fact that I was trying to build everything using `gcc-4.3`, I got strange behaviour of pfinet and spend a week trying to figure out the reason. * **Try to start the mountee during initialization of `unionfs`** *(4 Jul)* Initially the mountee was started at the first lookup. Now it is started immediately after initialization of `unionmount`. * **Fix the patches in `--mount` option series** *(5 Jul)* The patches have been reviewed by **antrik**. I corrected them and posted them to the ML for final reviews. * **Orphan the mountee after starting it** *(7 Jul)* Orphaning the mountee after starting it up seems to be a nice work-around for the necessity of keeping a proxy node in unionmount in simple use-cases. It is possible that this functionality will provided as a separate patch (without inclusion in master) should it turn out that orphaning the mountee is a bad idea. * **Decide which RPCs should be forwarded to the mountee and how this should happen** *(10 Jul)* This is the primary requirement in being able to proxy the control port of `unionmount`. * **Fix the patches the have already been commented on** *(14 Jul)* The new patches I have submitted have been reviewed; also, the older patches have been reviewed again, which required correcting them. * **Add the `--no-mount` option** *(14 Jul)* Using the `--no-mount` and `--mount` options, the user can decide whether unionmount should be completely transparent (i.e. most control-port RPCs forwarded to the mountee) or not. * **Make `unionmount` go away when the mountee goes away** *(14 Jul)* `unionmount` makes sense only while the mountee is running, so it has to go away as soon as the mountee has been shut down for some reason. * **Proxy the control port of `unionmount`** *(14 Jul)* For `unionmount` to become transparent, most of the RPCs invoked on the its control port should be forwarded to the mountee. * **Fix adding filesystems to `unionmount`** *(16 Jul)* `settrans -a foo unionfs -a -u -t ` worked, but `settrans -a foo unionfs -u -t -a ` didn't. The problem was that in a series of rebase operations I accidentally left the "Orphan the mountee" commit out and the problem appeared when the `start_mountee` function tried to attach the mountee. Of course, this is not the definite solution, since I don't know why should the attempt to attach the mountee work in the former case and fail in the latter, but I will leave the investigation for some future time. * **Create the patch for supplying the mountee with a port to the underlying node of unionfs** *(17 Jul)* Such functionality makes `unionmount` even more transparent. * **Try to make `eth-multiplexer` work with static instances of `devnode`** *(3 Aug)* A static `devnode` translator is a `devnode` translator which is told to use the eth-multiplexer's pseudo master device port via the "-M" option. Technically it looks like `settrans -a devnode -M `, where `` is the node on which eth-multiplexer is running. The problem was in the fact that the root node of `eth-multiplexer` was not treated completely similarly as other nodes; specifically no device port was created for it. Minor modifications to some conditions solved the problem. * **Add the `MASTER` node to `eth-multiplexer`** *(5 Aug)* The `MASTER` node, published by eth-multiplexer, allows creating any number of virtual devices. This node is mainly accessed by static instances of `devnode` to setup their corresponding virtual devices. * **Add support for priorities** *(6 Aug)* Now the mountee's filesystem can be configured to "lie" beneath other filesystems. * **Use `unionmount` to merge the virtual filesystem of `eth-multiplexer` with its underlying filesystem** *(7 Aug)* `eth-multiplexer` can is unionmounted to "lie beneath" it's underlying filesystem. If, for example, the multiplexer is unionmounted on `veth/`, the user can both set (static) `devnode` translator on the nodes shown in `veth/` and belonging to the underlying filesystem and create normal virtual multiplexer devices by accessing any node (not present in the underlying filesystem) and opening a device using the port to the node as a pseudo device port. * **Rename the `MASTER` node into `.MASTER`** (7 Aug) This name seems more natural for a special-purpose node. * **Set the stat information for `eth-multiplexer` nodes in `netfs_validate_stat`** (9 Aug) In the initial version the stat information was set up properly only at device creation. Before that the stat information was copied from the underlying node, which baffled `unionmount`. Now the stat information is setup in `netfs_validate_stat`. * **Supply the mountee with the real root.** *(14 Aug)* Since the mountee is *not attached* to its underlying node, it is okay to supply it with the real root node of `unionfs`. The mountee's filesystem will not obscure the `unionfs`'s one because the mountee is *not attached* to the root node. --- # Google Summer of Code: 2008 Project: Namespace-based translator selection --- ## Current Task Write the filesystem proxy for namespace-based translator selection (*nsmux*). The code is at . --- ###Did this week * Modified the node cache so that it maintains shadow nodes alive. ###Plans for the next week * Implement the shutting down of translator stacks when *nsmux* is asked to go away (in case **antrik** considers that necessary). * Make *nsmux* provide the access to the translator stack of the real node, in case a translator (mainly, a filter) should ask for its underlying node to be opened in O_NOTRANS mode. --- ###Current Status ####DONE: * The skeleton which mirrors the filesystem. * Provide proxy nodes (modify the standard version of netfs_S_dir_lookup). ####TODO: * Create the generic filtering translator. * Create the translator '0' (providing the untranslated version of the node). * Create the "recursive wrappers" for one-node translators. * Create special translators for the main proxy so that its functionality should be complete. * Implement sharing of dynamic translator stacks where possible. * Make dynamic translators go away as soon as they are not required. * Refine the skeleton in several places so that it should become faster and more reliable. * Kill bugs. * Integrate nsmux upstream. * Solve the libtrivfs stacking issue. * Patch libnetfs (it does not support file_get_translator_cntl, for instance). --- ###Progress ####8: Fri Sep 19: > Modified the ncache so that it now maintains shadow nodes (and directory nodes too, it is a side effect at the moment) alive. ####7: Sat Aug 30 - Fri Sep 5: > Added the code for shutting down dynamic translator stacks. ####6: Mon Aug 4 - Fri Aug 29: > Implemented the proxy nodes. ####5: Thu Jul 24 - Thu Jul 24: > Created a *libnetfs*-based one-node translator, working exactly like the *libtrivfs*-based translator I had written before; the former, however, can be included in a translator stack. ####4: Tue Jul 22 - Thu Jul 24: > Attempted to make a *libtrivfs*-based translator to be able to be stacked upon itself (to be able to receive a translator on top of itself, more exactly); attempted to borrow some code from *libnetfs* but this didn't bring any results. ####3: Sun Jul 20 - Tue Jul 22: > Implemented the possibility to propagate a translator on all files belonging to a directory 'dir' in the request of the type 'dir,,x/'. ####2: Thu Jul 17 - Fri Jul 18: > Extended the lookup code in *nsmux* to allow for looking up nodes like 'file,,x' and added the possibility to escape the double-comma in the following way: ',,,'. ####1: Mon Jul 12 - Tue Jul 13: > Implemented a simple *libtrivfs*-based translator to test the lookup code for *nsmux*. ####0: Sat Jul 12 - Sat Jul 12: > Made small changes to the code of *filterfs* to fit the needs of *nsmux*. --- ## Completed Tasks ####2: Sat May 3 - Fri Jul 17: > Write a translator that should filter the contents of the directory it is set on according to some property. The property can be an arbitrary command. > The code is at . ####1: Mon Apr 28 - Wed Apr 30: > Wrote a Python extension module in C for retreiving the uptime. The module is based on the code of *w*. ####0: Sun Apr 27: > Followed the code of *dmesgd* () kindly offered by **bddebian** and rewrote it from scratch as a tutorial.