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Ryan Moeller 5c0061345b
Cross-platform xattr user namespace compatibility
ZFS on Linux originally implemented xattr namespaces in a way that is
incompatible with other operating systems.  On illumos, xattrs do not
have namespaces.  Every xattr name is visible.  FreeBSD has two
universally defined namespaces: EXTATTR_NAMESPACE_USER and
EXTATTR_NAMESPACE_SYSTEM.  The system namespace is used for protected
FreeBSD-specific attributes such as MAC labels and pnfs state.  These
attributes have the namespace string "freebsd:system:" prefixed to the
name in the encoding scheme used by ZFS.  The user namespace is used
for general purpose user attributes and obeys normal access control
mechanisms.  These attributes have no namespace string prefixed, so
xattrs written on illumos are accessible in the user namespace on
FreeBSD, and xattrs written to the user namespace on FreeBSD are
accessible by the same name on illumos.

Linux has several xattr namespaces.  On Linux, ZFS encodes the
namespace in the xattr name for every namespace, including the user
namespace.  As a consequence, an xattr in the user namespace with the
name "foo" is stored by ZFS with the name "user.foo" and therefore
appears on FreeBSD and illumos to have the name "user.foo" rather than
"foo".  Conversely, none of the xattrs written on FreeBSD or illumos
are accessible on Linux unless the name happens to be prefixed with one
of the Linux xattr namespaces, in which case the namespace is stripped
from the name.  This makes xattrs entirely incompatible between Linux
and other platforms.

We want to make the encoding of user namespace xattrs compatible across
platforms.  A critical requirement of this compatibility is for xattrs
from existing pools from FreeBSD and illumos to be accessible by the
same names in the user namespace on Linux.  It is also necessary that
existing pools with xattrs written by Linux retain access to those
xattrs by the same names on Linux.  Making user namespace xattrs from
Linux accessible by the correct names on other platforms is important.
The handling of other namespaces is not required to be consistent.

Add a fallback mechanism for listing and getting xattrs to treat xattrs
as being in the user namespace if they do not match a known prefix.

Do not allow setting or getting xattrs with a name that is prefixed
with one of the namespace names used by ZFS on supported platforms.

Allow choosing between legacy illumos and FreeBSD compatibility and
legacy Linux compatibility with a new tunable.  This facilitates
replication and migration of pools between hosts with different
compatibility needs.

The tunable controls whether or not to prefix the namespace to the
name.  If the xattr is already present with the alternate prefix,
remove it so only the new version persists.  By default the platform's
existing convention is used.

Reviewed-by: Christian Schwarz <christian.schwarz@nutanix.com>
Reviewed-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #11919
2022-02-15 16:35:30 -08:00
.github Remove unused files from GitHub runners 2022-02-09 11:50:13 -08:00
cmd Rename fallthrough to zfs_fallthrough 2022-02-15 08:58:59 -08:00
config Propagate KERNEL_* to *.spec 2022-02-09 13:27:11 -08:00
contrib contrib: rename initrd READMEs to README.md 2022-02-11 11:44:27 -08:00
etc Add --enable=all to ShellCheck by default 2022-02-07 11:59:09 -08:00
include Cross-platform xattr user namespace compatibility 2022-02-15 16:35:30 -08:00
lib module: icp: remove unused (and mostly faked) cm_{{min,max}_key_length,mech_flags} 2022-02-15 16:25:52 -08:00
man Cross-platform xattr user namespace compatibility 2022-02-15 16:35:30 -08:00
module Cross-platform xattr user namespace compatibility 2022-02-15 16:35:30 -08:00
rpm contrib: rename initrd READMEs to README.md 2022-02-11 11:44:27 -08:00
scripts Add --enable=all to ShellCheck by default 2022-02-07 11:59:09 -08:00
tests Cross-platform xattr user namespace compatibility 2022-02-15 16:35:30 -08:00
udev Udev rules: remove zvol compat symlinks (without the leading zvol/) 2021-07-06 13:41:17 -07:00
.editorconfig Add an .editorconfig; document git whitespace settings 2020-01-27 13:32:52 -08:00
.gitignore Add FreeBSD support to OpenZFS 2020-04-14 11:36:28 -07:00
.gitmodules .gitmodules: link to openzfs github repository 2021-04-12 09:37:23 -07:00
AUTHORS Add zstd support to zfs 2020-08-20 10:30:06 -07:00
autogen.sh Cause autogen.sh to fail if autoreconf fails 2018-07-06 09:27:37 -07:00
CODE_OF_CONDUCT.md Replace ZFS on Linux references with OpenZFS 2020-10-08 20:10:13 -07:00
configure.ac Linux 5.16 compat: don't use XSTATE_XSAVE to save FPU state 2022-02-09 12:50:10 -08:00
copy-builtin copy-builtin: posix conformance 2021-05-08 08:58:26 -07:00
COPYRIGHT Fix typos 2020-06-09 21:24:09 -07:00
LICENSE Update build system and packaging 2018-05-29 16:00:33 -07:00
Makefile.am Clean up CSTYLEDs 2022-01-26 11:38:52 -08:00
META Linux 5.15 compat: META (#12824) 2021-12-07 15:35:42 -08:00
NEWS Fix NEWS file 2020-08-26 21:44:41 -07:00
NOTICE Update build system and packaging 2018-05-29 16:00:33 -07:00
README.md README: Update OpenZFS website url 2022-01-06 16:25:01 -08:00
RELEASES.md Add RELEASES.md file 2021-04-02 16:33:40 -07:00
TEST Remove CI builder customization from TEST 2020-03-16 10:46:03 -07:00
zfs.release.in

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OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.

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Official Resources

Installation

Full documentation for installing OpenZFS on your favorite operating system can be found at the Getting Started Page.

Contribute & Develop

We have a separate document with contribution guidelines.

We have a Code of Conduct.

Release

OpenZFS is released under a CDDL license. For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197

Supported Kernels

  • The META file contains the officially recognized supported Linux kernel versions.
  • Supported FreeBSD versions are any supported branches and releases starting from 12.2-RELEASE.