Author: zbyniu Date: Mon Sep 21 23:32:23 2009 GMT Module: packages Tag: HEAD ---- Log message: - fresh snap from git
---- Files affected: packages/kernel: kernel-aufs2.patch (1.5 -> 1.6) ---- Diffs: ================================================================ Index: packages/kernel/kernel-aufs2.patch diff -u packages/kernel/kernel-aufs2.patch:1.5 packages/kernel/kernel-aufs2.patch:1.6 --- packages/kernel/kernel-aufs2.patch:1.5 Tue Jul 21 09:46:58 2009 +++ packages/kernel/kernel-aufs2.patch Tue Sep 22 01:32:18 2009 @@ -1,6 +1,6 @@ -diff -urN linux-2.6.30.org/Documentation/ABI/testing/debugfs-aufs linux-2.6.30/Documentation/ABI/testing/debugfs-aufs ---- linux-2.6.30.org/Documentation/ABI/testing/debugfs-aufs 1970-01-01 01:00:00.000000000 +0100 -+++ linux-2.6.30/Documentation/ABI/testing/debugfs-aufs 2009-07-21 08:54:18.000000000 +0200 +diff -uprN -x .git linux-2.6.31/Documentation/ABI/testing/debugfs-aufs aufs2-2.6.git/Documentation/ABI/testing/debugfs-aufs +--- linux-2.6.31/Documentation/ABI/testing/debugfs-aufs 1970-01-01 00:00:00.000000000 +0000 ++++ aufs2-2.6.git/Documentation/ABI/testing/debugfs-aufs 2009-09-14 14:52:35.032396516 +0000 @@ -0,0 +1,40 @@ +What: /debug/aufs/si_<id>/ +Date: March 2009 @@ -42,9 +42,9 @@ + When the aufs mount option 'noxino' is specified, it + will be empty. About XINO files, see + Documentation/filesystems/aufs/aufs.5 in detail. -diff -urN linux-2.6.30.org/Documentation/ABI/testing/sysfs-aufs linux-2.6.30/Documentation/ABI/testing/sysfs-aufs ---- linux-2.6.30.org/Documentation/ABI/testing/sysfs-aufs 1970-01-01 01:00:00.000000000 +0100 -+++ linux-2.6.30/Documentation/ABI/testing/sysfs-aufs 2009-07-21 08:54:18.000000000 +0200 +diff -uprN -x .git linux-2.6.31/Documentation/ABI/testing/sysfs-aufs aufs2-2.6.git/Documentation/ABI/testing/sysfs-aufs +--- linux-2.6.31/Documentation/ABI/testing/sysfs-aufs 1970-01-01 00:00:00.000000000 +0000 ++++ aufs2-2.6.git/Documentation/ABI/testing/sysfs-aufs 2009-09-14 14:52:35.032396516 +0000 @@ -0,0 +1,25 @@ +What: /sys/fs/aufs/si_<id>/ +Date: March 2009 @@ -71,9 +71,1479 @@ + When the aufs mount option 'noxino' is specified, it + will be empty. About XINO files, see + Documentation/filesystems/aufs/aufs.5 in detail. -diff -urN linux-2.6.30.org/fs/aufs/aufs.h linux-2.6.30/fs/aufs/aufs.h ---- linux-2.6.30.org/fs/aufs/aufs.h 1970-01-01 01:00:00.000000000 +0100 -+++ linux-2.6.30/fs/aufs/aufs.h 2009-07-21 08:54:18.000000000 +0200 +diff -uprN -x .git linux-2.6.31/Documentation/filesystems/aufs/README aufs2-2.6.git/Documentation/filesystems/aufs/README +--- linux-2.6.31/Documentation/filesystems/aufs/README 1970-01-01 00:00:00.000000000 +0000 ++++ aufs2-2.6.git/Documentation/filesystems/aufs/README 2009-09-21 21:48:58.761610020 +0000 +@@ -0,0 +1,342 @@ ++ ++Aufs2 -- advanced multi layered unification filesystem version 2 ++http://aufs.sf.net ++Junjiro R. Okajima ++ ++ ++0. Introduction ++---------------------------------------- ++In the early days, aufs was entirely re-designed and re-implemented ++Unionfs Version 1.x series. After many original ideas, approaches, ++improvements and implementations, it becomes totally different from ++Unionfs while keeping the basic features. ++Recently, Unionfs Version 2.x series begin taking some of the same ++approaches to aufs1's. ++Unionfs is being developed by Professor Erez Zadok at Stony Brook ++University and his team. ++ ++This version of AUFS, aufs2 has several purposes. ++- to be reviewed easily and widely. ++- to make the source files simpler and smaller by dropping several ++ original features. ++ ++Through this work, I found some bad things in aufs1 source code and ++fixed them. Some of the dropped features will be reverted in the future, ++but not all I'm afraid. ++Aufs2 supports linux-2.6.27 and later. If you want older kernel version ++support, try aufs1 from CVS on SourceForge. ++ ++Note: it becomes clear that "Aufs was rejected. Let's give it up." ++According to Christoph Hellwig, linux rejects all union-type filesystems ++but UnionMount. ++<http://marc.info/?l=linux-kernel&m=123938533724484&w=2> ++ ++ ++1. Features ++---------------------------------------- ++- unite several directories into a single virtual filesystem. The member ++ directory is called as a branch. ++- you can specify the permission flags to the branch, which are 'readonly', ++ 'readwrite' and 'whiteout-able.' ++- by upper writable branch, internal copyup and whiteout, files/dirs on ++ readonly branch are modifiable logically. ++- dynamic branch manipulation, add, del. ++- etc... ++ ++Also there are many enhancements in aufs1, such as: ++- readdir(3) in userspace. ++- keep inode number by external inode number table ++- keep the timestamps of file/dir in internal copyup operation ++- seekable directory, supporting NFS readdir. ++- support mmap(2) including /proc/PID/exe symlink, without page-copy ++- whiteout is hardlinked in order to reduce the consumption of inodes ++ on branch ++- do not copyup, nor create a whiteout when it is unnecessary ++- revert a single systemcall when an error occurs in aufs ++- remount interface instead of ioctl ++- maintain /etc/mtab by an external command, /sbin/mount.aufs. ++- loopback mounted filesystem as a branch ++- kernel thread for removing the dir who has a plenty of whiteouts ++- support copyup sparse file (a file which has a 'hole' in it) ++- default permission flags for branches ++- selectable permission flags for ro branch, whether whiteout can ++ exist or not ++- export via NFS. ++- support <sysfs>/fs/aufs and <debugfs>/aufs. ++- support multiple writable branches, some policies to select one ++ among multiple writable branches. ++- a new semantics for link(2) and rename(2) to support multiple ++ writable branches. ++- no glibc changes are required. ++- pseudo hardlink (hardlink over branches) ++- allow a direct access manually to a file on branch, e.g. bypassing aufs. ++ including NFS or remote filesystem branch. ++- and more... ++ ++Currently these features are dropped temporary from this version, aufs2. ++See design/08plan.txt in detail. ++- test only the highest one for the directory permission (dirperm1) ++- show whiteout mode (shwh) ++- copyup on open (coo=) ++- nested mount, i.e. aufs as readonly no-whiteout branch of another aufs ++ (robr) ++- statistics of aufs thread (/sys/fs/aufs/stat) ++- delegation mode (dlgt) ++ a delegation of the internal branch access to support task I/O ++ accounting, which also supports Linux Security Modules (LSM) mainly ++ for Suse AppArmor. ++- intent.open/create (file open in a single lookup) ++ ++Features or just an idea in the future (see also design/*.txt), ++- reorder the branch index without del/re-add. ++- permanent xino files for NFSD ++- an option for refreshing the opened files after add/del branches ++- 'move' policy for copy-up between two writable branches, after ++ checking free space. ++- O_DIRECT ++- light version, without branch manipulation. (unnecessary?) ++- copyup in userspace ++- inotify in userspace ++- readv/writev ++- xattr, acl ++ ++ ++2. Download ++---------------------------------------- ++Kindly one of aufs user, the Center for Scientific Computing and Free ++Software (C3SL), Federal University of Parana offered me a public GIT ++tree space. ++ ++There are three GIT trees, aufs2-2.6, aufs2-standalone and aufs2-util. ++While the aufs2-util is always necessary, you need either of aufs2-2.6 ++or aufs2-standalone. ++ ++The aufs2-2.6 tree includes the whole linux-2.6 GIT tree, ++git://git.kernel.org/.../torvalds/linux-2.6.git. ++And you cannot select CONFIG_AUFS_FS=m for this version, eg. you cannot ++build aufs2 as an externel kernel module. ++If you already have linux-2.6 GIT tree, you may want to pull and merge ++the "aufs2" branch from this tree. ++ ++On the other hand, the aufs2-standalone tree has only aufs2 source files ++and a necessary patch, and you can select CONFIG_AUFS_FS=m. In other ++words, the aufs2-standalone tree is generated from aufs2-2.6 tree by, ++- extract new files and modifications. ++- generate some patch files from modifications. ++- generate a ChangeLog file from git-log. ++- commit the files newly and no log messages. this is not git-pull. ++ ++Both of aufs2-2.6 and aufs2-standalone trees have a branch whose name is ++in form of "aufs2-xx" where "xx" represents the linux kernel version, ++"linux-2.6.xx". ++ ++o aufs2-2.6 tree ++$ git clone --reference /your/linux-2.6/git/tree \ ++ http://git.c3sl.ufpr.br/pub/scm/aufs/aufs2-2.6.git \ ++ aufs2-2.6.git ++- if you don't have linux-2.6 GIT tree, then remove "--reference ..." ++$ cd aufs2-2.6.git ++$ git checkout origin/aufs2-xx # for instance, aufs2-27 for linux-2.6.27 ++ # aufs2 (no -xx) for the latest -rc version. ++ ++o aufs2-standalone tree ++$ git clone http://git.c3sl.ufpr.br/pub/scm/aufs/aufs2-standalone.git \ ++ aufs2-standalone.git ++$ cd aufs2-standalone.git ++$ git checkout origin/aufs2-xx # for instance, aufs2-27 for linux-2.6.27 ++ # aufs2 (no -xx) for the latest -rc version. ++ ++o aufs2-util tree ++$ git clone http://git.c3sl.ufpr.br/pub/scm/aufs/aufs2-util.git \ ++ aufs2-util.git ++$ cd aufs2-util.git ++- no particular tag/branch currently. ++ ++o for advanced users ++$ git clone git://git.kernel.org/.../torvalds/linux-2.6.git linux-2.6.git ++ It will take very long time. ++ ++$ cd linux-2.6.git ++$ git remote add aufs2 http://git.c3sl.ufpr.br/pub/scm/aufs/aufs2-2.6.git ++$ git checkout -b aufs2-27 v2.6.27 ++$ git pull aufs2 aufs2-27 ++ It may take long time again. ++ Once pulling completes, you've got linux-2.6.27 and aufs2 for it in a ++ branch named aufs2-27, and you can configure and build it. ++ ++Or ++ ++$ git checkout -t -b aufs2 master ++$ git pull aufs2 aufs2 ++ then you've got the latest linux kernel and the latest aufs2 in a ++ branch named aufs2, and you can configure and build it. ++ But aufs is released once a week, so you may meet a compilation error ++ due to mismatching between the mainline and aufs2. ++ ++Or you may want build linux-2.6.xx.yy instead of linux-2.6.xx, then here ++is an approach using linux-2.6-stable GIT tree. ++ ++$ cd linux-2.6.git/.. ++$ git clone -q --reference ./linux-2.6.git git://git.kernel.org/.../linux-2.6-stable.git \ ++ linux-2.6-stable.git ++ It will take very long time. ++ ++$ cd linux-2.6-stable.git ++$ git remote add aufs2 http://git.c3sl.ufpr.br/pub/scm/aufs/aufs2-2.6.git ++$ git checkout -b aufs2-27.1 v2.6.27.1 ++$ git pull aufs2 aufs2-27 ++ then you've got linux-2.6.27.1 and aufs2 for 2.6.27 in a branch named ++ aufs2-27.1, and you can configure and build it. ++ But the changes made by v2.6.xx.yy may conflict with aufs2-xx, since ++ aufs2-xx is for v2.6.xx only. In this case, you may find some patchces ++ for v2.6.xx.yy in aufs2-standalone.git#aufs2-xx branch if someone else ++ have ever requested me to support v2.6.xx.yy and I did it. ++ ++You can also check what was changed by pulling aufs2. ++$ git diff v2.6.27.1..aufs2-27.1 ++ ++If you want to check the changed files other than fs/aufs, then try this. ++$ git diff v2.6.27.1..aufs2-27.1 | ++> awk ' ++> /^diff / {new=1} ++> /^diff.*aufs/ {new=0} ++> new {print} ++> ' ++ ++ ++3. Configuration and Compilation ++---------------------------------------- ++For aufs2-2.6 tree, ++- enable CONFIG_EXPERIMENTAL and CONFIG_AUFS_FS. ++- set other aufs configurations if necessary. ++ ++For aufs2-standalone tree, ++There are several ways to build. ++ ++You may feel why aufs2-standalone.patch needs to export so many kernel ++symbols. Because you selected aufs2-standalone tree instead of aufs2-2.6 ++tree. The number of necessary symbols to export essentially is zero. ++All other symbols are for the external module. ++If you don't like aufs2-standalone.patch, then try aufs2-2.6 tree. ++ ++1. ++- apply ./aufs2-kbuild.patch to your kernel source files. ++- apply ./aufs2-base.patch too. ++- apply ./aufs2-standalone.patch too, if you have a plan to set ++ CONFIG_AUFS_FS=m. otherwise you don't need ./aufs2-standalone.patch. ++- copy ./{Documentation,fs,include} files to your kernel source tree. ++- enable CONFIG_EXPERIMENTAL and CONFIG_AUFS_FS, you can select either ++ =m or =y. ++- and build your kernel as usual. ++- install it and reboot your system. ++ ++2. ++- module only (CONFIG_AUFS_FS=m). ++- apply ./aufs2-base.patch to your kernel source files. ++- apply ./aufs2-standalone.patch too. ++- build your kernel and reboot. ++- edit ./config.mk and set other aufs configurations if necessary. ++ Note: You should read ./fs/aufs/Kconfig carefully which describes ++ every aufs configurations. ++- build the module by simple "make". ++- you can specify ${KDIR} make variable which points to your kernel ++ source tree. ++- copy the build ./aufs.ko to /lib/modules/..., and run depmod -a (or ++ reboot simply). ++- no need to apply aufs2-kbuild.patch, nor copying source files to your ++ kernel source tree. ++ ++And then, ++- read README in aufs2-util, build and install it ++- if you want to use readdir(3) in userspace, then run ++ "make install_ulib" too. And refer to the aufs manual in detail. ++ ++ ++4. Usage ++---------------------------------------- ++At first, make sure aufs2-util are installed, and please read the aufs ++manual, aufs.5 in aufs2-util.git tree. ++$ man -l aufs.5 ++ ++And then, ++$ mkdir /tmp/rw /tmp/aufs ++# mount -t aufs -o br=/tmp/rw:${HOME} none /tmp/aufs ++ ++Here is another example. The result is equivalent. ++# mount -t aufs -o br=/tmp/rw=rw:${HOME}=ro none /tmp/aufs ++ Or ++# mount -t aufs -o br:/tmp/rw none /tmp/aufs ++# mount -o remount,append:${HOME} /tmp/aufs ++ ++Then, you can see whole tree of your home dir through /tmp/aufs. If ++you modify a file under /tmp/aufs, the one on your home directory is ++not affected, instead the same named file will be newly created under ++/tmp/rw. And all of your modification to a file will be applied to ++the one under /tmp/rw. This is called the file based Copy on Write ++(COW) method. ++Aufs mount options are described in aufs.5. ++ ++Additionally, there are some sample usages of aufs which are a ++diskless system with network booting, and LiveCD over NFS. ++See sample dir in CVS tree on SourceForge. ++ ++ ++5. Contact ++---------------------------------------- ++When you have any problems or strange behaviour in aufs, please let me ++know with: ++- /proc/mounts (instead of the output of mount(8)) ++- /sys/module/aufs/* ++- /sys/fs/aufs/* (if you have them) ++- /debug/aufs/* (if you have them) ++- linux kernel version ++ if your kernel is not plain, for example modified by distributor, ++ the url where i can download its source is necessary too. ++- aufs version which was printed at loading the module or booting the ++ system, instead of the date you downloaded. ++- configuration (define/undefine CONFIG_AUFS_xxx) ++- kernel configuration or /proc/config.gz (if you have it) ++- behaviour which you think to be incorrect ++- actual operation, reproducible one is better ++- mailto: aufs-users at lists.sourceforge.net ++ ++Usually, I don't watch the Public Areas(Bugs, Support Requests, Patches, ++and Feature Requests) on SourceForge. Please join and write to ++aufs-users ML. ++ ++ ++6. Acknowledgements ++---------------------------------------- ++Thanks to everyone who have tried and are using aufs, whoever ++have reported a bug or any feedback. ++ ++Especially donors: ++Tomas Matejicek(slax.org) made a donation (much more than once). ++Dai Itasaka made a donation (2007/8). ++Chuck Smith made a donation (2008/4, 10 and 12). ++Henk Schoneveld made a donation (2008/9). ++Chih-Wei Huang, ASUS, CTC donated Eee PC 4G (2008/10). ++Francois Dupoux made a donation (2008/11). ++Bruno Cesar Ribas and Luis Carlos Erpen de Bona, C3SL serves public ++aufs2 GIT tree (2009/2). ++William Grant made a donation (2009/3). ++Patrick Lane made a donation (2009/4). ++The Mail Archive (mail-archive.com) made donations (2009/5). ++Nippy Networks (Ed Wildgoose) a donation (2009/7). ++ ++Thank you very much. ++Donations are always, including future donations, very important and ++helpful for me to keep on developing aufs. ++ ++ ++7. ++---------------------------------------- ++If you are an experienced user, no explanation is needed. Aufs is ++just a linux filesystem. ++ ++ ++Enjoy! ++ ++# Local variables: ; ++# mode: text; ++# End: ; +diff -uprN -x .git linux-2.6.31/Documentation/filesystems/aufs/design/01intro.txt aufs2-2.6.git/Documentation/filesystems/aufs/design/01intro.txt +--- linux-2.6.31/Documentation/filesystems/aufs/design/01intro.txt 1970-01-01 00:00:00.000000000 +0000 ++++ aufs2-2.6.git/Documentation/filesystems/aufs/design/01intro.txt 2009-09-21 21:48:58.761610020 +0000 +@@ -0,0 +1,137 @@ ++ ++# Copyright (C) 2005-2009 Junjiro R. Okajima ++# ++# This program is free software; you can redistribute it and/or modify ++# it under the terms of the GNU General Public License as published by ++# the Free Software Foundation; either version 2 of the License, or ++# (at your option) any later version. ++# ++# This program is distributed in the hope that it will be useful, ++# but WITHOUT ANY WARRANTY; without even the implied warranty of ++# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ++# GNU General Public License for more details. ++# ++# You should have received a copy of the GNU General Public License ++# along with this program; if not, write to the Free Software ++# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA ++ ++Introduction ++---------------------------------------- ++ ++aufs [ei ju: ef es] | [a u f s] ++1. abbrev. for "advanced multi-layered unification filesystem". ++2. abbrev. for "another unionfs". ++3. abbrev. for "auf das" in German which means "on the" in English. ++ Ex. "Butter aufs Brot"(G) means "butter onto bread"(E). ++ But "Filesystem aufs Filesystem" is hard to understand. ++ ++AUFS is a filesystem with features: ++- multi layered stackable unification filesystem, the member directory ++ is called as a branch. ++- branch permission and attribute, 'readonly', 'real-readonly', ++ 'readwrite', 'whiteout-able', 'link-able whiteout' and their ++ combination. ++- internal "file copy-on-write". ++- logical deletion, whiteout. ++- dynamic branch manipulation, adding, deleting and changing permission. ++- allow bypassing aufs, user's direct branch access. ++- external inode number translation table and bitmap which maintains the ++ persistent aufs inode number. ++- seekable directory, including NFS readdir. ++- file mapping, mmap and sharing pages. ++- pseudo-link, hardlink over branches. ++- loopback mounted filesystem as a branch. ++- several policies to select one among multiple writable branches. ++- revert a single systemcall when an error occurs in aufs. ++- and more... ++ ++ ++Multi Layered Stackable Unification Filesystem ++---------------------------------------------------------------------- ++Most people already knows what it is. ++It is a filesystem which unifies several directories and provides a ++merged single directory. When users access a file, the access will be ++passed/re-directed/converted (sorry, I am not sure which English word is ++correct) to the real file on the member filesystem. The member ++filesystem is called 'lower filesystem' or 'branch' and has a mode ++'readonly' and 'readwrite.' And the deletion for a file on the lower ++readonly branch is handled by creating 'whiteout' on the upper writable ++branch. ++ ++On LKML, there have been discussions about UnionMount (Jan Blunck and ++Bharata B Rao) and Unionfs (Erez Zadok). They took different approaches ++to implement the merged-view. ++The former tries putting it into VFS, and the latter implements as a ++separate filesystem. ++(If I misunderstand about these implementations, please let me know and ++I shall correct it. Because it is a long time ago when I read their ++source files last time). ++UnionMount's approach will be able to small, but may be hard to share ++branches between several UnionMount since the whiteout in it is ++implemented in the inode on branch filesystem and always ++shared. According to Bharata's post, readdir does not seems to be ++finished yet. ++Unionfs has a longer history. When I started implementing a stacking filesystem ++(Aug 2005), it already existed. It has virtual super_block, inode, ++dentry and file objects and they have an array pointing lower same kind ++objects. After contributing many patches for Unionfs, I re-started my ++project AUFS (Jun 2006). ++ ++In AUFS, the structure of filesystem resembles to Unionfs, but I ++implemented my own ideas, approaches and enhancements and it became ++totally different one. ++ ++ ++Several characters/aspects of aufs ++---------------------------------------------------------------------- ++ ++Aufs has several characters or aspects. ++1. a filesystem, callee of VFS helper ++2. sub-VFS, caller of VFS helper for branches ++3. a virtual filesystem which maintains persistent inode number ++4. reader/writer of files on branches such like an application ++ ++1. Caller of VFS Helper ++As an ordinary linux filesystem, aufs is a callee of VFS. For instance, ++unlink(2) from an application reaches sys_unlink() kernel function and ++then vfs_unlink() is called. vfs_unlink() is one of VFS helper and it ++calls filesystem specific unlink operation. Actually aufs implements the ++unlink operation but it behaves like a redirector. ++ ++2. Caller of VFS Helper for Branches ++aufs_unlink() passes the unlink request to the branch filesystem as if ++it were called from VFS. So the called unlink operation of the branch ++filesystem acts as usual. As a caller of VFS helper, aufs should handle ++every necessary pre/post operation for the branch filesystem. ++- acquire the lock for the parent dir on a branch ++- lookup in a branch ++- revalidate dentry on a branch ++- mnt_want_write() for a branch ++- vfs_unlink() for a branch ++- mnt_drop_write() for a branch ++- release the lock on a branch ++ ++3. Persistent Inode Number ++One of the most important issue for a filesystem is to maintain inode ++numbers. This is particularly important to support exporting a ++filesystem via NFS. Aufs is a virtual filesystem which doesn't have a ++backend block device for its own. But some storage is necessary to ++maintain inode number. It may be a large space and may not suit to keep ++in memory. Aufs rents some space from its first writable branch ++filesystem (by default) and creates file(s) on it. These files are ++created by aufs internally and removed soon (currently) keeping opened. ++Note: Because these files are removed, they are totally gone after ++ unmounting aufs. It means the inode numbers are not persistent ++ across unmount or reboot. I have a plan to make them really ++ persistent which will be important for aufs on NFS server. ++ ++4. Read/Write Files Internally (copy-on-write) ++Because a branch can be readonly, when you write a file on it, aufs will ++"copy-up" it to the upper writable branch internally. And then write the ++originally requested thing to the file. Generally kernel doesn't ++open/read/write file actively. In aufs, even a single write may cause a ++internal "file copy". This behaviour is very similar to cp(1) command. ++ ++Some people may think it is better to pass such work to user space ++helper, instead of doing in kernel space. Actually I am still thinking ++about it. But currently I have implemented it in kernel space. +diff -uprN -x .git linux-2.6.31/Documentation/filesystems/aufs/design/02struct.txt aufs2-2.6.git/Documentation/filesystems/aufs/design/02struct.txt +--- linux-2.6.31/Documentation/filesystems/aufs/design/02struct.txt 1970-01-01 00:00:00.000000000 +0000 ++++ aufs2-2.6.git/Documentation/filesystems/aufs/design/02struct.txt 2009-09-21 21:48:58.761610020 +0000 +@@ -0,0 +1,218 @@ ++ ++# Copyright (C) 2005-2009 Junjiro R. Okajima ++# ++# This program is free software; you can redistribute it and/or modify ++# it under the terms of the GNU General Public License as published by ++# the Free Software Foundation; either version 2 of the License, or ++# (at your option) any later version. ++# ++# This program is distributed in the hope that it will be useful, ++# but WITHOUT ANY WARRANTY; without even the implied warranty of ++# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ++# GNU General Public License for more details. ++# ++# You should have received a copy of the GNU General Public License ++# along with this program; if not, write to the Free Software ++# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA ++ ++Basic Aufs Internal Structure ++ ++Superblock/Inode/Dentry/File Objects ++---------------------------------------------------------------------- ++As like an ordinary filesystem, aufs has its own ++superblock/inode/dentry/file objects. All these objects have a ++dynamically allocated array and store the same kind of pointers to the ++lower filesystem, branch. ++For example, when you build a union with one readwrite branch and one ++readonly, mounted /au, /rw and /ro respectively. ++- /au = /rw + /ro ++- /ro/fileA exists but /rw/fileA ++ ++Aufs lookup operation finds /ro/fileA and gets dentry for that. These ++pointers are stored in a aufs dentry. The array in aufs dentry will be, ++- [0] = NULL ++- [1] = /ro/fileA ++ ++This style of an array is essentially same to the aufs ++superblock/inode/dentry/file objects. ++ ++Because aufs supports manipulating branches, ie. add/delete/change ++dynamically, these objects has its own generation. When branches are ++changed, the generation in aufs superblock is incremented. And a ++generation in other object are compared when it is accessed. ++When a generation in other objects are obsoleted, aufs refreshes the ++internal array. ++ ++ ++Superblock ++---------------------------------------------------------------------- ++Additionally aufs superblock has some data for policies to select one ++among multiple writable branches, XIB files, pseudo-links and kobject. ++See below in detail. ++About the policies which supports copy-down a directory, see policy.txt ++too. ++ ++ ++Branch and XINO(External Inode Number Translation Table) ++---------------------------------------------------------------------- ++Every branch has its own xino (external inode number translation table) ++file. The xino file is created and unlinked by aufs internally. When two ++members of a union exist on the same filesystem, they share the single ++xino file. ++The struct of a xino file is simple, just a sequence of aufs inode ++numbers which is indexed by the lower inode number. ++In the above sample, assume the inode number of /ro/fileA is i111 and ++aufs assigns the inode number i999 for fileA. Then aufs writes 999 as ++4(8) bytes at 111 * 4(8) bytes offset in the xino file. ++ ++When the inode numbers are not contiguous, the xino file will be sparse ++which has a hole in it and doesn't consume as much disk space as it ++might appear. If your branch filesystem consumes disk space for such ++holes, then you should specify 'xino=' option at mounting aufs. <<Diff was trimmed, longer than 597 lines>> ---- CVS-web: http://cvs.pld-linux.org/cgi-bin/cvsweb.cgi/packages/kernel/kernel-aufs2.patch?r1=1.5&r2=1.6&f=u _______________________________________________ pld-cvs-commit mailing list [email protected] http://lists.pld-linux.org/mailman/listinfo/pld-cvs-commit
