You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
88 lines
3.8 KiB
88 lines
3.8 KiB
This is a small patch adding user extended attribute support[1] for local files
|
|
to tdeio. With the patch in place user xattrs are preserved when copying or
|
|
moving files on the local system[2]. It relies on libattr[3] to do the heavy
|
|
lifting.
|
|
|
|
The code adds a call to attr_copy_file in libattr that copies the user xattrs
|
|
from the source file to the destination file. The call is made after the
|
|
source file has been closed and immediately before the source file is deleted
|
|
(in the case that a move is being done). This code is based on the sample
|
|
code[4] provided with libattr (examples/copyattr.c).
|
|
|
|
This code has been in daily use by the author of this patch for just over five
|
|
years without any issues. What's missing though is the addition of tests for
|
|
xattr and libattr support at configuration/compile time. The code I've added
|
|
is enclosed by '#ifdef DO_USER_XATTR_COPYING' statements so a test should be
|
|
added that sets this macro[5] if configure-time tests show that xattrs/libattr
|
|
are working. I've added a preliminary test to CMakeLists.txt but I'm not sure
|
|
it's correct. Alternatively uncomment the '#define DO_USER_XATTR_COPYING 1'
|
|
statement at the top of the code to force my code to be enabled. Ensuring that
|
|
the cmake test working correctly needs to be done before general release.
|
|
|
|
This code has been tested on select Ubuntu Linux releases (natty, precise,
|
|
xenial, and jammy) using x86_64 Linux kernels 3.14.1, 4.18.3, and 5.15.0.
|
|
Tested filesystems are ext4 and squashfs.
|
|
|
|
As far as cross-platform availability goes this code is only known to work on
|
|
Linux[6][7]. That said, this code adds functionality that (as far as I'm aware)
|
|
isn't currently present in TDE on any of the platforms it runs on. In other
|
|
words, even if it only runs on Linux in its current state there is no loss of
|
|
functionality on any other platforms (just a lack of a gaining a feature). In
|
|
addition, determining the proper location to insert the library call was the
|
|
hard part with the actual implementation being quite straightforward. Adding
|
|
additional backends for other platforms should be pretty easy.
|
|
|
|
To test the code build and install it[8] then run the following from the
|
|
commandline in e.g. Konsole:
|
|
|
|
$ cd PATH_SUPPORTING_USER_XATTRS_AT_THE_FILESYSTEM_LEVEL
|
|
$ touch attr_test
|
|
$ setfattr -n "user.AttributeName" -v "Attribute value" attr_test
|
|
$ kfmclient copy attr_test attr_test.copy
|
|
$ getfattr -d attr_test*
|
|
|
|
The final command should output (minus the indents):
|
|
|
|
# file: attr_test
|
|
user.AttributeName="Attribute value"
|
|
|
|
# file: attr_test.copy
|
|
user.AttributeName="Attribute value"
|
|
|
|
Enjoy!
|
|
|
|
|
|
- Alex Kent Hajnal (AKH) 2022-12-21
|
|
|
|
|
|
|
|
[1] This includeds all attributes residing (on Linux) in the "user" namespace.
|
|
ACLs, etc. are not copied.
|
|
|
|
See the xattr(7) and e.g. the getfattr(1) manpages for more info.
|
|
|
|
[2] The underlying filesytems must, of course, have xattr support enabled.
|
|
This should be the case by default on modern systems that support xattrs.
|
|
|
|
[3] This is libattr1 and libattr1-dev on Ubuntu.
|
|
|
|
See http://savannah.nongnu.org/projects/attr for more info.
|
|
See also https://github.com/philips/attr
|
|
|
|
[4] The code that this patch is based on is licensed GPL v2 (or later).
|
|
|
|
[5] One has to use '#define DO_USER_XATTR_COPYING 1'; specifying instead
|
|
'#define DO_USER_XATTR_COPYING' doesn't enable the code (at least on my
|
|
system).
|
|
|
|
[6] I'm not sure which non-Linux platforms (if any) libattr runs on.
|
|
|
|
[7] Another known issue is namespaces. Linux, FreeBSD, and NetBSD support
|
|
xattrs using the 'user' namespace. Solaris and OSX support user xattrs
|
|
but do not support namespaces.
|
|
(source: File::ExtAttr(3pm), personal testing)
|
|
|
|
[8] Instead of doing a full install one can simply copy the updated library:
|
|
|
|
cp -va "BUILD_DIR/tdeio/libtdeio.so.14.0.0" /opt/trinity/lib/ && ldconfig
|