packages: kernel/kernel.spec, kernel/kernel-aufs3.patch (NEW), kernel/kerne...
arekm
arekm at pld-linux.org
Wed Aug 24 13:37:43 CEST 2011
Author: arekm Date: Wed Aug 24 11:37:43 2011 GMT
Module: packages Tag: HEAD
---- Log message:
- switch to aufs3
---- Files affected:
packages/kernel:
kernel.spec (1.958 -> 1.959) , kernel-aufs3.patch (NONE -> 1.1) (NEW), kernel-aufs2.patch (1.23 -> NONE) (REMOVED)
---- Diffs:
================================================================
Index: packages/kernel/kernel.spec
diff -u packages/kernel/kernel.spec:1.958 packages/kernel/kernel.spec:1.959
--- packages/kernel/kernel.spec:1.958 Wed Aug 24 12:22:19 2011
+++ packages/kernel/kernel.spec Wed Aug 24 13:37:36 2011
@@ -252,17 +252,17 @@
# http://download.filesystems.org/unionfs/unionfs-2.x/unionfs-2.5.8_for_2.6.38-rc7.diff.gz
Patch140: kernel-unionfs.patch
-# http://git.c3sl.ufpr.br/pub/scm/aufs/aufs2-standalone.git, read README
+# git://aufs.git.sourceforge.net/gitroot/aufs/aufs3-standalone.git, read README
# Patch creation:
-# git clone http://git.c3sl.ufpr.br/pub/scm/aufs/aufs2-standalone.git
-# cd aufs2-standalone
-# git checkout -b aufs2.1 origin/aufs2.1
-# cat aufs2-kbuild.patch aufs2-base.patch aufs2-standalone.patch > ~/rpm/packages/kernel/kernel-aufs2.patch
+# git clone git://aufs.git.sourceforge.net/gitroot/aufs/aufs3-standalone.git
+# cd aufs3-standalone
+# git checkout -b aufs3.0 origin/aufs3.0
+# cat aufs3-kbuild.patch aufs3-base.patch aufs3-standalone.patch > ~/rpm/packages/kernel/kernel-aufs3.patch
# mkdir linux
# cp -a Documentation fs include linux
-# diff -urN /usr/share/empty linux >> ~/rpm/packages/kernel/kernel-aufs2.patch
+# diff -urN /usr/share/empty linux >> ~/rpm/packages/kernel/kernel-aufs3.patch
#
-Patch145: kernel-aufs2.patch
+Patch145: kernel-aufs3.patch
Patch146: kernel-aufs2-unionfs.patch
Patch147: kernel-aufs2-no-const-grsec.patch
Patch148: kernel-aufs2-reiser4.patch
@@ -1519,6 +1519,9 @@
All persons listed below can be reached at <cvs_login>@pld-linux.org
$Log$
+Revision 1.959 2011/08/24 11:37:36 arekm
+- switch to aufs3
+
Revision 1.958 2011/08/24 10:22:19 arekm
- typo
================================================================
Index: packages/kernel/kernel-aufs3.patch
diff -u /dev/null packages/kernel/kernel-aufs3.patch:1.1
--- /dev/null Wed Aug 24 13:37:43 2011
+++ packages/kernel/kernel-aufs3.patch Wed Aug 24 13:37:36 2011
@@ -0,0 +1,30342 @@
+aufs3.0 kbuild patch
+
+diff --git a/fs/Kconfig b/fs/Kconfig
+index 19891aa..b660b64 100644
+--- a/fs/Kconfig
++++ b/fs/Kconfig
+@@ -208,6 +208,7 @@ source "fs/pstore/Kconfig"
+ source "fs/sysv/Kconfig"
+ source "fs/ufs/Kconfig"
+ source "fs/exofs/Kconfig"
++source "fs/aufs/Kconfig"
+
+ endif # MISC_FILESYSTEMS
+
+diff --git a/fs/Makefile b/fs/Makefile
+index fb68c2b..c031a85 100644
+--- a/fs/Makefile
++++ b/fs/Makefile
+@@ -124,3 +124,4 @@ obj-$(CONFIG_GFS2_FS) += gfs2/
+ obj-$(CONFIG_EXOFS_FS) += exofs/
+ obj-$(CONFIG_CEPH_FS) += ceph/
+ obj-$(CONFIG_PSTORE) += pstore/
++obj-$(CONFIG_AUFS_FS) += aufs/
+diff --git a/include/linux/Kbuild b/include/linux/Kbuild
+index 01f6362..8b3b9f1 100644
+--- a/include/linux/Kbuild
++++ b/include/linux/Kbuild
+@@ -65,6 +65,7 @@ header-y += atmppp.h
+ header-y += atmsap.h
+ header-y += atmsvc.h
+ header-y += audit.h
++header-y += aufs_type.h
+ header-y += auto_fs.h
+ header-y += auto_fs4.h
+ header-y += auxvec.h
+aufs3.0 base patch
+
+diff --git a/fs/namei.c b/fs/namei.c
+index 14ab8d3..eb4aef1 100644
+--- a/fs/namei.c
++++ b/fs/namei.c
+@@ -1697,7 +1697,7 @@ static struct dentry *__lookup_hash(struct qstr *name,
+ * needs parent already locked. Doesn't follow mounts.
+ * SMP-safe.
+ */
+-static struct dentry *lookup_hash(struct nameidata *nd)
++struct dentry *lookup_hash(struct nameidata *nd)
+ {
+ return __lookup_hash(&nd->last, nd->path.dentry, nd);
+ }
+diff --git a/fs/splice.c b/fs/splice.c
+index aa866d3..19afec6 100644
+--- a/fs/splice.c
++++ b/fs/splice.c
+@@ -1085,8 +1085,8 @@ EXPORT_SYMBOL(generic_splice_sendpage);
+ /*
+ * Attempt to initiate a splice from pipe to file.
+ */
+-static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
+- loff_t *ppos, size_t len, unsigned int flags)
++long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
++ loff_t *ppos, size_t len, unsigned int flags)
+ {
+ ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
+ loff_t *, size_t, unsigned int);
+@@ -1113,9 +1113,9 @@ static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
+ /*
+ * Attempt to initiate a splice from a file to a pipe.
+ */
+-static long do_splice_to(struct file *in, loff_t *ppos,
+- struct pipe_inode_info *pipe, size_t len,
+- unsigned int flags)
++long do_splice_to(struct file *in, loff_t *ppos,
++ struct pipe_inode_info *pipe, size_t len,
++ unsigned int flags)
+ {
+ ssize_t (*splice_read)(struct file *, loff_t *,
+ struct pipe_inode_info *, size_t, unsigned int);
+diff --git a/include/linux/namei.h b/include/linux/namei.h
+index eba45ea..21ed6c9 100644
+--- a/include/linux/namei.h
++++ b/include/linux/namei.h
+@@ -82,6 +82,7 @@ extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
+ extern struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
+ int (*open)(struct inode *, struct file *));
+
++extern struct dentry *lookup_hash(struct nameidata *nd);
+ extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
+
+ extern int follow_down_one(struct path *);
+diff --git a/include/linux/splice.h b/include/linux/splice.h
+index 997c3b4..be9a153 100644
+--- a/include/linux/splice.h
++++ b/include/linux/splice.h
+@@ -89,4 +89,10 @@ extern int splice_grow_spd(struct pipe_inode_info *, struct splice_pipe_desc *);
+ extern void splice_shrink_spd(struct pipe_inode_info *,
+ struct splice_pipe_desc *);
+
++extern long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
++ loff_t *ppos, size_t len, unsigned int flags);
++extern long do_splice_to(struct file *in, loff_t *ppos,
++ struct pipe_inode_info *pipe, size_t len,
++ unsigned int flags);
++
+ #endif
+aufs3.0 standalone patch
+
+diff --git a/fs/file_table.c b/fs/file_table.c
+index 01e4c1e..0e800e2 100644
+--- a/fs/file_table.c
++++ b/fs/file_table.c
+@@ -443,6 +443,8 @@ void file_sb_list_del(struct file *file)
+ }
+ }
+
++EXPORT_SYMBOL(file_sb_list_del);
++
+ #ifdef CONFIG_SMP
+
+ /*
+diff --git a/fs/inode.c b/fs/inode.c
+index 43566d1..4291eae 100644
+--- a/fs/inode.c
++++ b/fs/inode.c
+@@ -69,6 +69,7 @@ static DEFINE_SPINLOCK(inode_lru_lock);
+
+ __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_sb_list_lock);
+ __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_wb_list_lock);
++EXPORT_SYMBOL(inode_sb_list_lock);
+
+ /*
+ * iprune_sem provides exclusion between the icache shrinking and the
+diff --git a/fs/namei.c b/fs/namei.c
+index eb4aef1..66d04c6 100644
+--- a/fs/namei.c
++++ b/fs/namei.c
+@@ -365,6 +365,7 @@ int deny_write_access(struct file * file)
+
+ return 0;
+ }
++EXPORT_SYMBOL(deny_write_access);
+
+ /**
+ * path_get - get a reference to a path
+@@ -1701,6 +1702,7 @@ struct dentry *lookup_hash(struct nameidata *nd)
+ {
+ return __lookup_hash(&nd->last, nd->path.dentry, nd);
+ }
++EXPORT_SYMBOL(lookup_hash);
+
+ /**
+ * lookup_one_len - filesystem helper to lookup single pathname component
+diff --git a/fs/namespace.c b/fs/namespace.c
+index fe59bd1..7d3843f 100644
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -1508,6 +1508,7 @@ int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
+ }
+ return 0;
+ }
++EXPORT_SYMBOL(iterate_mounts);
+
+ static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end)
+ {
+diff --git a/fs/notify/group.c b/fs/notify/group.c
+index d309f38..f0e9568 100644
+--- a/fs/notify/group.c
++++ b/fs/notify/group.c
+@@ -22,6 +22,7 @@
+ #include <linux/srcu.h>
+ #include <linux/rculist.h>
+ #include <linux/wait.h>
++#include <linux/module.h>
+
+ #include <linux/fsnotify_backend.h>
+ #include "fsnotify.h"
+@@ -70,6 +71,7 @@ void fsnotify_put_group(struct fsnotify_group *group)
+ if (atomic_dec_and_test(&group->refcnt))
+ fsnotify_destroy_group(group);
+ }
++EXPORT_SYMBOL(fsnotify_put_group);
+
+ /*
+ * Create a new fsnotify_group and hold a reference for the group returned.
+@@ -102,3 +104,4 @@ struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
+
+ return group;
+ }
++EXPORT_SYMBOL(fsnotify_alloc_group);
+diff --git a/fs/notify/mark.c b/fs/notify/mark.c
+index 252ab1f..2199b9b 100644
+--- a/fs/notify/mark.c
++++ b/fs/notify/mark.c
+@@ -112,6 +112,7 @@ void fsnotify_put_mark(struct fsnotify_mark *mark)
+ if (atomic_dec_and_test(&mark->refcnt))
+ mark->free_mark(mark);
+ }
++EXPORT_SYMBOL(fsnotify_put_mark);
+
+ /*
+ * Any time a mark is getting freed we end up here.
+@@ -189,6 +190,7 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
+ if (unlikely(atomic_dec_and_test(&group->num_marks)))
+ fsnotify_final_destroy_group(group);
+ }
++EXPORT_SYMBOL(fsnotify_destroy_mark);
+
+ void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask)
+ {
+@@ -276,6 +278,7 @@ err:
+
+ return ret;
+ }
++EXPORT_SYMBOL(fsnotify_add_mark);
+
+ /*
+ * clear any marks in a group in which mark->flags & flags is true
+@@ -331,6 +334,7 @@ void fsnotify_init_mark(struct fsnotify_mark *mark,
+ atomic_set(&mark->refcnt, 1);
+ mark->free_mark = free_mark;
+ }
++EXPORT_SYMBOL(fsnotify_init_mark);
+
+ static int fsnotify_mark_destroy(void *ignored)
+ {
+diff --git a/fs/open.c b/fs/open.c
+index b52cf01..c1b341c 100644
+--- a/fs/open.c
++++ b/fs/open.c
+@@ -60,6 +60,7 @@ int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
+ mutex_unlock(&dentry->d_inode->i_mutex);
+ return ret;
+ }
++EXPORT_SYMBOL(do_truncate);
+
+ static long do_sys_truncate(const char __user *pathname, loff_t length)
+ {
+diff --git a/fs/splice.c b/fs/splice.c
+index 19afec6..11f07f8 100644
+--- a/fs/splice.c
++++ b/fs/splice.c
+@@ -1109,6 +1109,7 @@ long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
+
+ return splice_write(pipe, out, ppos, len, flags);
+ }
++EXPORT_SYMBOL(do_splice_from);
+
+ /*
+ * Attempt to initiate a splice from a file to a pipe.
+@@ -1135,6 +1136,7 @@ long do_splice_to(struct file *in, loff_t *ppos,
+
+ return splice_read(in, ppos, pipe, len, flags);
+ }
++EXPORT_SYMBOL(do_splice_to);
+
+ /**
+ * splice_direct_to_actor - splices data directly between two non-pipes
+diff --git a/security/commoncap.c b/security/commoncap.c
+index a93b3b7..024282c 100644
+--- a/security/commoncap.c
++++ b/security/commoncap.c
+@@ -978,4 +978,4 @@ int cap_file_mmap(struct file *file, uns
+ }
+ return ret;
+ }
+-
++EXPORT_SYMBOL(cap_file_mmap);
+diff --git a/security/device_cgroup.c b/security/device_cgroup.c
+index 1be6826..215278c 100644
+--- a/security/device_cgroup.c
++++ b/security/device_cgroup.c
+@@ -508,6 +508,7 @@ found:
+
+ return -EPERM;
+ }
++EXPORT_SYMBOL(__devcgroup_inode_permission);
+
+ int devcgroup_inode_mknod(int mode, dev_t dev)
+ {
+diff --git a/security/security.c b/security/security.c
+index 4ba6d4c..9f64bb8 100644
+--- a/security/security.c
++++ b/security/security.c
+@@ -373,6 +373,7 @@ int security_path_rmdir(struct path *dir, struct dentry *dentry)
+ return 0;
+ return security_ops->path_rmdir(dir, dentry);
+ }
++EXPORT_SYMBOL(security_path_rmdir);
+
+ int security_path_unlink(struct path *dir, struct dentry *dentry)
+ {
+@@ -389,6 +390,7 @@ int security_path_symlink(struct path *dir, struct dentry *dentry,
+ return 0;
+ return security_ops->path_symlink(dir, dentry, old_name);
+ }
++EXPORT_SYMBOL(security_path_symlink);
+
+ int security_path_link(struct dentry *old_dentry, struct path *new_dir,
+ struct dentry *new_dentry)
+@@ -397,6 +399,7 @@ int security_path_link(struct dentry *old_dentry, struct path *new_dir,
+ return 0;
+ return security_ops->path_link(old_dentry, new_dir, new_dentry);
+ }
++EXPORT_SYMBOL(security_path_link);
+
+ int security_path_rename(struct path *old_dir, struct dentry *old_dentry,
+ struct path *new_dir, struct dentry *new_dentry)
+@@ -415,6 +418,7 @@ int security_path_truncate(struct path *path)
+ return 0;
+ return security_ops->path_truncate(path);
+ }
++EXPORT_SYMBOL(security_path_truncate);
+
+ int security_path_chmod(struct dentry *dentry, struct vfsmount *mnt,
+ mode_t mode)
+@@ -423,6 +427,7 @@ int security_path_chmod(struct dentry *dentry, struct vfsmount *mnt,
+ return 0;
+ return security_ops->path_chmod(dentry, mnt, mode);
+ }
++EXPORT_SYMBOL(security_path_chmod);
+
+ int security_path_chown(struct path *path, uid_t uid, gid_t gid)
+ {
+@@ -430,6 +435,7 @@ int security_path_chown(struct path *path, uid_t uid, gid_t gid)
+ return 0;
+ return security_ops->path_chown(path, uid, gid);
+ }
++EXPORT_SYMBOL(security_path_chown);
+
+ int security_path_chroot(struct path *path)
+ {
+@@ -506,6 +512,7 @@ int security_inode_readlink(struct dentry *dentry)
+ return 0;
+ return security_ops->inode_readlink(dentry);
+ }
++EXPORT_SYMBOL(security_inode_readlink);
+
+ int security_inode_follow_link(struct dentry *dentry, struct nameidata *nd)
+ {
+@@ -520,6 +527,7 @@ int security_inode_permission(struct inode *inode, int mask)
+ return 0;
+ return security_ops->inode_permission(inode, mask, 0);
+ }
++EXPORT_SYMBOL(security_inode_permission);
+
+ int security_inode_exec_permission(struct inode *inode, unsigned int flags)
+ {
+@@ -626,6 +634,7 @@ int security_file_permission(struct file *file, int mask)
+
+ return fsnotify_perm(file, mask);
+ }
++EXPORT_SYMBOL(security_file_permission);
+
+ int security_file_alloc(struct file *file)
+ {
+@@ -653,6 +662,7 @@ int security_file_mmap(struct file *file, unsigned long reqprot,
+ return ret;
+ return ima_file_mmap(file, prot);
+ }
++EXPORT_SYMBOL(security_file_mmap);
+
+ int security_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
+ unsigned long prot)
+diff -urN /usr/share/empty/Documentation/ABI/testing/debugfs-aufs linux/Documentation/ABI/testing/debugfs-aufs
+--- /usr/share/empty/Documentation/ABI/testing/debugfs-aufs 1970-01-01 01:00:00.000000000 +0100
++++ linux/Documentation/ABI/testing/debugfs-aufs 2011-08-24 13:30:24.727980364 +0200
+@@ -0,0 +1,37 @@
++What: /debug/aufs/si_<id>/
++Date: March 2009
++Contact: J. R. Okajima <hooanon05 at yahoo.co.jp>
++Description:
++ Under /debug/aufs, a directory named si_<id> is created
++ per aufs mount, where <id> is a unique id generated
++ internally.
++
++What: /debug/aufs/si_<id>/xib
++Date: March 2009
++Contact: J. R. Okajima <hooanon05 at yahoo.co.jp>
++Description:
++ It shows the consumed blocks by xib (External Inode Number
++ Bitmap), its block size and file size.
++ When the aufs mount option 'noxino' is specified, it
++ will be empty. About XINO files, see the aufs manual.
++
++What: /debug/aufs/si_<id>/xino0, xino1 ... xinoN
++Date: March 2009
++Contact: J. R. Okajima <hooanon05 at yahoo.co.jp>
++Description:
++ It shows the consumed blocks by xino (External Inode Number
++ Translation Table), its link count, block size and file
++ size.
++ When the aufs mount option 'noxino' is specified, it
++ will be empty. About XINO files, see the aufs manual.
++
++What: /debug/aufs/si_<id>/xigen
++Date: March 2009
++Contact: J. R. Okajima <hooanon05 at yahoo.co.jp>
++Description:
++ It shows the consumed blocks by xigen (External Inode
++ Generation Table), its block size and file size.
++ If CONFIG_AUFS_EXPORT is disabled, this entry will not
++ be created.
++ When the aufs mount option 'noxino' is specified, it
++ will be empty. About XINO files, see the aufs manual.
+diff -urN /usr/share/empty/Documentation/ABI/testing/sysfs-aufs linux/Documentation/ABI/testing/sysfs-aufs
+--- /usr/share/empty/Documentation/ABI/testing/sysfs-aufs 1970-01-01 01:00:00.000000000 +0100
++++ linux/Documentation/ABI/testing/sysfs-aufs 2011-08-24 13:30:24.727980364 +0200
+@@ -0,0 +1,24 @@
++What: /sys/fs/aufs/si_<id>/
++Date: March 2009
++Contact: J. R. Okajima <hooanon05 at yahoo.co.jp>
++Description:
++ Under /sys/fs/aufs, a directory named si_<id> is created
++ per aufs mount, where <id> is a unique id generated
++ internally.
++
++What: /sys/fs/aufs/si_<id>/br0, br1 ... brN
++Date: March 2009
++Contact: J. R. Okajima <hooanon05 at yahoo.co.jp>
++Description:
++ It shows the abolute path of a member directory (which
++ is called branch) in aufs, and its permission.
++
++What: /sys/fs/aufs/si_<id>/xi_path
++Date: March 2009
++Contact: J. R. Okajima <hooanon05 at yahoo.co.jp>
++Description:
++ It shows the abolute path of XINO (External Inode Number
++ Bitmap, Translation Table and Generation Table) file
++ even if it is the default path.
++ When the aufs mount option 'noxino' is specified, it
++ will be empty. About XINO files, see the aufs manual.
+diff -urN /usr/share/empty/Documentation/filesystems/aufs/design/01intro.txt linux/Documentation/filesystems/aufs/design/01intro.txt
+--- /usr/share/empty/Documentation/filesystems/aufs/design/01intro.txt 1970-01-01 01:00:00.000000000 +0100
++++ linux/Documentation/filesystems/aufs/design/01intro.txt 2011-08-24 13:30:24.727980364 +0200
+@@ -0,0 +1,162 @@
++
++# Copyright (C) 2005-2011 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,
++Bharata B Rao and Valerie Aurora) 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.
++There are several missing features known in this implementations such as
++- for users, the inode number may change silently. eg. copy-up.
++- link(2) may break by copy-up.
++- read(2) may get an obsoleted filedata (fstat(2) too).
++- fcntl(F_SETLK) may be broken by copy-up.
++- unnecessary copy-up may happen, for example mmap(MAP_PRIVATE) after
++ open(O_RDWR).
++
++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.
++
++Comparing DM snapshot and fs based implementation
++- the number of bytes to be copied between devices is much smaller.
++- the type of filesystem must be one and only.
++- the fs must be writable, no readonly fs, even for the lower original
++ device. so the compression fs will not be usable. but if we use
++ loopback mount, we may address this issue.
++ for instance,
++ mount /cdrom/squashfs.img /sq
++ losetup /sq/ext2.img
++ losetup /somewhere/cow
++ dmsetup "snapshot /dev/loop0 /dev/loop1 ..."
++- it will be difficult (or needs more operations) to extract the
++ difference between the original device and COW.
++- DM snapshot-merge may help a lot when users try merging. in the
++ fs-layer union, users will use rsync(1).
++
++
++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
<<Diff was trimmed, longer than 597 lines>>
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