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John Ferlan f23d4bbce3 storage: Fix implementation of no-overwrite for file system backend
https://bugzilla.redhat.com/show_bug.cgi?id=1363586

Commit id '27758859' introduced the "NO_OVERWRITE" flag check for
file system backends; however, the implementation, documentation,
and algorithm was inconsistent. For the "flag" description for the
API the flag was described as "Do not overwrite existing pool";
however, within the storage backend code the flag is described
as "it probes to determine if filesystem already exists on the
target device, renurning an error if exists".

The code itself was implemented using the paradigm to set up the
superblock probe by creating a filter that would cause the code
to only search for the provided format type. If that type wasn't
found, then the algorithm would return success allowing the caller
to format the device. If the format type already existed on the
device, then the code would fail indicating that the a filesystem
of the same type existed on the device.

The result is that if someone had a file system of one type on the
device, it was possible to overwrite it if a different format type
was specified in updated XML effectively trashing whatever was on
the device already.

This patch alters what NO_OVERWRITE does for a file system backend
to be more realistic and consistent with what should be expected when
the caller requests to not overwrite the data on the disk.

Rather than filter results based on the expected format type, the
code will allow success/failure be determined solely on whether the
blkid_do_probe calls finds some known format on the device. This
adjustment also allows removal of the virStoragePoolProbeResult
enum that was under utilized.

If it does find a formatted file system different errors will be
generated indicating a file system of a specific type already exists
or a file system of some other type already exists.

In the original virsh support commit id 'ddcd5674', the description
for '--no-overwrite' within the 'pool-build' command help output
has an ambiguous "of this type" included in the short description.
Compared to the longer description within the "Build a given pool."
section of the virsh.pod file it's more apparent that the meaning
of this flag would cause failure if a probe of the target already
has a filesystem.

So this patch also modifies the short description to just be the
antecedent of the 'overwrite' flag, which matches the API description.
This patch also modifies the grammar in virsh.pod for no-overwrite
as well as reworking the paragraph formats to make it easier to read.

Signed-off-by: John Ferlan <jferlan@redhat.com>
2017-01-10 08:44:50 -05:00
.gnulib@e210a3cbae maint: update to latest gnulib 2017-01-02 11:44:46 +01:00
build-aux prohibit-duplicate-header: print file name and line 2016-06-23 12:48:40 +02:00
daemon secret: add support for value change events 2017-01-09 16:42:04 +00:00
docs NEWS: Update for virtio-pci by default for mach-virt guests 2017-01-10 12:33:54 +01:00
examples secret: add support for value change events 2017-01-09 16:42:04 +00:00
gnulib build: drop hack for old mingw ssize_t 2016-07-12 08:57:13 -06:00
include/libvirt perf: Add cache_l1d perf event support 2017-01-09 18:15:31 -05:00
m4 virt-nss: Introduce more checks before enabling NSS 2017-01-02 13:25:42 +01:00
po s390: Cpu driver support for update and compare 2017-01-06 12:24:56 +01:00
src storage: Fix implementation of no-overwrite for file system backend 2017-01-10 08:44:50 -05:00
tests qemu: Use virtio-pci by default for mach-virt guests 2017-01-10 12:33:53 +01:00
tools storage: Fix implementation of no-overwrite for file system backend 2017-01-10 08:44:50 -05:00
.ctags maint: Make ctags work out of the box 2013-07-18 08:47:21 +02:00
.dir-locals.el build: avoid tabs that failed syntax-check 2012-09-06 09:43:46 -06:00
.gitignore admin: Add an example demonstrating how to use the logging APIs 2016-12-15 10:36:23 +01:00
.gitmodules make .gnulib a submodule 2009-07-08 16:17:51 +02:00
.mailmap maint: update .mailmap for recent contributions 2015-03-20 06:17:55 -06:00
AUTHORS.in Change maintainers list 2016-02-12 13:10:05 +03:00
COPYING maint: follow recommended practice for using LGPL 2013-05-20 14:15:21 -06:00
COPYING.LESSER maint: Remove control characters from LGPL license file 2015-09-25 09:16:24 +02:00
ChangeLog-old Fix typos in src/* 2014-04-21 16:49:08 -06:00
HACKING HACKING: Reduce vertical whitespace 2017-01-04 16:06:04 +01:00
Makefile.am dist: Speed up distribution compression 2016-06-30 16:05:24 +02:00
Makefile.nonreentrant cfg.mk: use a single regex for all non-reentrant functions 2016-06-15 15:00:56 +02:00
README Correct typos in the documentation (Atsushi SAKAI) 2008-01-24 10:15:13 +00:00
README-hacking docs: update README-hacking 2014-05-06 16:20:24 -06:00
TODO Update todo list file to point at bugzilla/website 2010-10-13 16:45:26 +01:00
autobuild.sh maint: Switch to xz compressed PAX release archives 2016-06-15 18:53:34 +02:00
autogen.sh maint: improve usage of autogen's --no-git 2015-02-06 11:35:29 -07:00
bootstrap maint: Sync bootstrap after gnulib update 2017-01-02 12:10:26 +01:00
bootstrap.conf hvsupport: use a regex instead of XML::XPath 2016-07-19 18:42:44 +02:00
cfg.mk nssmock: Prefer free() over VIR_FREE() 2016-12-06 13:33:18 +01:00
config-post.h m4/virt-devmapper: use LIBVIRT_CHECK_(PKG|LIB) 2016-12-21 15:39:39 +01:00
configure.ac virt-nss: Introduce more checks before enabling NSS 2017-01-02 13:25:42 +01:00
libvirt-admin.pc.in Add libvirt-admin library 2015-06-16 13:46:20 +02:00
libvirt-lxc.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt-qemu.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt.spec.in libvirt.spec: Package libnss_libvirt_guest.so.2 2016-12-08 15:25:17 +01:00
mingw-libvirt.spec.in test: fix screenshot API impl 2016-12-08 10:57:32 +00:00
run.in Add PKG_CONFIG_PATH to run.in script. 2014-06-26 14:32:35 +01:00

README

         LibVirt : simple API for virtualization

  Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.

Daniel Veillard <veillard@redhat.com>