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d1333dd0fb
If you have a qcow2 file /path1/to/file pointed to by symlink
/path2/symlink, and pass qemu /path2/symlink, then qemu treats
a relative backing file in the qcow2 metadata as being relative
to /path2, not /path1/to. Yes, this means that it is possible
to create a qcow2 file where the choice of WHICH directory and
symlink you access its contents from will then determine WHICH
backing file (if any) you actually find; the results can be
rather screwy, but we have to match what qemu does.
Libvirt and qemu default to creating absolute backing file
names, so most users don't hit this. But at least VDSM uses
symlinks and relative backing names alongside the
--reuse-external flags to libvirt snapshot operations, with the
result that libvirt was failing to follow the intended chain of
backing files, and then backing files were not granted the
necessary sVirt permissions to be opened by qemu.
See https://bugzilla.redhat.com/show_bug.cgi?id=903248 for
more gory details. This fixes a regression introduced in
commit 8250783.
I tested this patch by creating the following chain:
ls /home/eblake/Downloads/Fedora.iso # raw file for base
cd /var/lib/libvirt/images
qemu-img create -f qcow2 \
-obacking_file=/home/eblake/Downloads/Fedora.iso,backing_fmt=raw one
mkdir sub
cd sub
ln -s ../one onelink
qemu-img create -f qcow2 \
-obacking_file=../sub/onelink,backing_fmt=qcow2 two
mv two ..
ln -s ../two twolink
qemu-img create -f qcow2 \
-obacking_file=../sub/twolink,backing_fmt=qcow2 three
mv three ..
ln -s ../three threelink
then pointing my domain at /var/lib/libvirt/images/sub/threelink.
Prior to this patch, I got complaints about missing backing
files; afterwards, I was able to verify that the backing chain
(and hence DAC and SELinux relabels) of the entire chain worked.
* src/util/virstoragefile.h (_virStorageFileMetadata): Add
directory member.
* src/util/virstoragefile.c (absolutePathFromBaseFile): Drop,
replaced by...
(virFindBackingFile): ...better function.
(virStorageFileGetMetadataInternal): Add an argument.
(virStorageFileGetMetadataFromFD, virStorageFileChainLookup)
(virStorageFileGetMetadata): Update callers.
112 lines
3.9 KiB
C
112 lines
3.9 KiB
C
/*
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* virstoragefile.h: file utility functions for FS storage backend
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*
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* Copyright (C) 2007-2009, 2012-2013 Red Hat, Inc.
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* Copyright (C) 2007-2008 Daniel P. Berrange
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see
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* <http://www.gnu.org/licenses/>.
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*
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* Author: Daniel P. Berrange <berrange@redhat.com>
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*/
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#ifndef __VIR_STORAGE_FILE_H__
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# define __VIR_STORAGE_FILE_H__
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# include "virutil.h"
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enum virStorageFileFormat {
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VIR_STORAGE_FILE_AUTO_SAFE = -2,
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VIR_STORAGE_FILE_AUTO = -1,
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VIR_STORAGE_FILE_NONE = 0,
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VIR_STORAGE_FILE_RAW,
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VIR_STORAGE_FILE_DIR,
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VIR_STORAGE_FILE_BOCHS,
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VIR_STORAGE_FILE_CLOOP,
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VIR_STORAGE_FILE_COW,
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VIR_STORAGE_FILE_DMG,
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VIR_STORAGE_FILE_ISO,
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VIR_STORAGE_FILE_QCOW,
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VIR_STORAGE_FILE_QCOW2,
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VIR_STORAGE_FILE_QED,
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VIR_STORAGE_FILE_VMDK,
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VIR_STORAGE_FILE_VPC,
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VIR_STORAGE_FILE_FAT,
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VIR_STORAGE_FILE_VHD,
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VIR_STORAGE_FILE_VDI,
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VIR_STORAGE_FILE_LAST,
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};
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VIR_ENUM_DECL(virStorageFileFormat);
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typedef struct _virStorageFileMetadata virStorageFileMetadata;
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typedef virStorageFileMetadata *virStorageFileMetadataPtr;
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struct _virStorageFileMetadata {
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char *backingStore; /* Canonical name (absolute file, or protocol) */
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char *backingStoreRaw; /* If file, original name, possibly relative */
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char *directory; /* The directory containing basename(backingStoreRaw) */
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int backingStoreFormat; /* enum virStorageFileFormat */
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bool backingStoreIsFile;
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virStorageFileMetadataPtr backingMeta;
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unsigned long long capacity;
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bool encrypted;
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};
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# ifndef DEV_BSIZE
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# define DEV_BSIZE 512
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# endif
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int virStorageFileProbeFormat(const char *path, uid_t uid, gid_t gid);
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int virStorageFileProbeFormatFromFD(const char *path,
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int fd);
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virStorageFileMetadataPtr virStorageFileGetMetadata(const char *path,
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int format,
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uid_t uid, gid_t gid,
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bool allow_probe);
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virStorageFileMetadataPtr virStorageFileGetMetadataFromFD(const char *path,
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int fd,
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int format);
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const char *virStorageFileChainLookup(virStorageFileMetadataPtr chain,
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const char *start,
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const char *name,
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virStorageFileMetadataPtr *meta,
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const char **parent)
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ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
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void virStorageFileFreeMetadata(virStorageFileMetadataPtr meta);
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int virStorageFileResize(const char *path, unsigned long long capacity);
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enum {
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VIR_STORAGE_FILE_SHFS_NFS = (1 << 0),
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VIR_STORAGE_FILE_SHFS_GFS2 = (1 << 1),
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VIR_STORAGE_FILE_SHFS_OCFS = (1 << 2),
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VIR_STORAGE_FILE_SHFS_AFS = (1 << 3),
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};
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int virStorageFileIsSharedFS(const char *path);
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int virStorageFileIsClusterFS(const char *path);
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int virStorageFileIsSharedFSType(const char *path,
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int fstypes);
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int virStorageFileGetLVMKey(const char *path,
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char **key);
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int virStorageFileGetSCSIKey(const char *path,
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char **key);
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#endif /* __VIR_STORAGE_FILE_H__ */
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