Hi, This series is supposed to pull out some of the problems from my “Generic file creation fallback” series.
The blk_truncate_for_formatting() function added there was buggy, as Maxim noted, in that it did not check whether blk_truncate() actually resized the block node to the target offset. One way to fix this is to add a parameter to it that forces the block driver to do so, and that is done by this series. I think this is generally useful (you can see the diff stat saldo is only +23 lines), because it allows us to drop a special check in qemu-img resize, and it fixes a bug in qed (which has relied on this behavior for over 8 years, but unfortunately bdrv_truncate()’s behavior changed quite exactly 8 years ago). However, in the process I noticed we actually don’t need blk_truncate_for_formatting(): The underlying problem is that some format drivers truncate their underlying file node to 0 before formatting it to drop all data. So they should pass exact=true, but they cannot, because this would break creation on block devices. Hence blk_truncate_for_formatting(). It turns out, though, that three of the four drivers in question don’t need to truncate their file node at all. The remaining one is qed which simply really should pass exact=true (it’s a bug fix). (I do drop those blk_truncate() invocations in this series, because otherwise I feel like it is impossible to decide whether they should get exact=false or exact=true. Either way is wrong.) Max Reitz (8): block: Handle filter truncation like native impl. block/cor: Drop cor_co_truncate() block: Do not truncate file node when formatting block: Add @exact parameter to bdrv_co_truncate() block: Evaluate @exact in protocol drivers block: Let format drivers pass @exact block: Pass truncate exact=true where reasonable Revert "qemu-img: Check post-truncation size" include/block/block.h | 6 ++--- include/block/block_int.h | 17 ++++++++++++- include/sysemu/block-backend.h | 4 +-- block/block-backend.c | 6 ++--- block/commit.c | 5 ++-- block/copy-on-read.c | 8 ------ block/crypto.c | 8 +++--- block/file-posix.c | 11 ++++++-- block/file-win32.c | 3 ++- block/gluster.c | 1 + block/io.c | 29 ++++++++++++--------- block/iscsi.c | 10 ++++++-- block/mirror.c | 4 +-- block/nfs.c | 2 +- block/parallels.c | 18 +++++++------ block/qcow.c | 9 ++----- block/qcow2-refcount.c | 2 +- block/qcow2.c | 45 +++++++++++++++++++++------------ block/qed.c | 3 ++- block/raw-format.c | 5 ++-- block/rbd.c | 1 + block/sheepdog.c | 5 ++-- block/ssh.c | 3 ++- block/vdi.c | 2 +- block/vhdx-log.c | 4 +-- block/vhdx.c | 7 +++--- block/vmdk.c | 8 +++--- block/vpc.c | 2 +- blockdev.c | 2 +- qemu-img.c | 46 ++++++++-------------------------- qemu-io-cmds.c | 7 +++++- tests/test-block-iothread.c | 8 +++--- 32 files changed, 157 insertions(+), 134 deletions(-) -- 2.21.0
