*** This series is based on v7 of my *** *** "blockdev: BlockBackend and media" series ***
The BDS filename field is generally only used when opening disk images or emitting error or warning messages, the only exception to this rule is the map command of qemu-img. However, using exact_filename there instead should not be a problem. Therefore, we can drop the filename field from the BlockDriverState and use a function instead which builds the filename from scratch when called. This is slower than reading a static char array but the problem of that static array is that it may become obsolete due to changes in any BlockDriverState or in the BDS graph. Using a function which rebuilds the filename every time it is called resolves this problem. The disadvantage of worse performance is negligible, on the other hand. After patch 2 of this series, which replaces some queries of BDS.filename by reads from somewhere else (mostly BDS.exact_filename), the filename field is only used when a disk image is opened or some message should be emitted, both of which cases do not suffer from the performance hit. http://lists.nongnu.org/archive/html/qemu-devel/2015-06/msg07025.html gives an example of how to achieve an outdated filename, so we do need this series. We can technically fix it differently (by appropriately invoking bdrv_refresh_filename()), but that is pretty difficult™. I find this series simpler and it it's something we wanted to do anyway. Regarding the fear that this might change current behavior, especially for libvirt which used filenames to identify nodes in the BDS graph: Since bdrv_open() already calls bdrv_refresh_filename() today, and apparently everything works fine, this series will most likely not break anything. The only thing that will change is if the BDS graph is dynamically reconfigured at runtime, and in that case it's most likely a bug fix. Also, I don't think libvirt supports such cases already. tl;dr: This series is a bug fix and I don't think it'll break legacy management applications relying on the filename to identify a BDS; as long as they are not trying to continue that practice with more advanced configurations (e.g. with Quorum). v5: (Rebased and addressed Eric's comments) - Patch 1: Do not pstrcpy() into a caller-supplied buffer, but g_strdup() instead [Eric] - Patch 2: Rebase conflicts - Patch 3: Drop bdrv_filename_alloc(), instead bdrv_filename() will allocate a buffer if NULL is specified - Patch 4: Use bdrv_filename() instead of bdrv_filename_alloc() - Patch 5: - Rebase conflicts - Use bdrv_filename() instead of bdrv_filename_alloc() git-backport-diff against v4: Key: [----] : patches are identical [####] : number of functional differences between upstream/downstream patch [down] : patch is downstream-only The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively 001/6:[0029] [FC] 'block: Change bdrv_get_encrypted_filename()' 002/6:[0004] [FC] 'block: Avoid BlockDriverState.filename' 003/6:[0040] [FC] 'block: Add bdrv_filename()' 004/6:[0002] [FC] 'qemu-img: Use bdrv_filename() for map' 005/6:[0093] [FC] 'block: Drop BlockDriverState.filename' 006/6:[----] [--] 'iotests: Test changed Quorum filename' Max Reitz (6): block: Change bdrv_get_encrypted_filename() block: Avoid BlockDriverState.filename block: Add bdrv_filename() qemu-img: Use bdrv_filename() for map block: Drop BlockDriverState.filename iotests: Test changed Quorum filename block.c | 105 +++++++++++++++++++++++++++++++++------------- block/commit.c | 4 +- block/gluster.c | 2 +- block/mirror.c | 16 +++++-- block/qapi.c | 4 +- block/raw-posix.c | 8 ++-- block/raw-win32.c | 4 +- block/raw_bsd.c | 4 +- block/vhdx-log.c | 5 ++- block/vmdk.c | 22 +++++++--- block/vpc.c | 7 +++- blockdev.c | 25 ++++++++--- include/block/block.h | 3 +- include/block/block_int.h | 1 - monitor.c | 5 ++- qemu-img.c | 14 ++++++- tests/qemu-iotests/041 | 17 ++++++-- 17 files changed, 179 insertions(+), 67 deletions(-) -- 2.6.1
