On Fri, Jun 28, 2024 at 11:20:58PM +0300, Nir Soffer wrote: > When opening an image with discard=off, we punch hole in the image when > writing zeroes, making the image sparse. This breaks users that want to > ensure that writes cannot fail with ENOSPACE by using fully allocated > images[1]. > > bdrv_co_pwrite_zeroes() correctly disables BDRV_REQ_MAY_UNMAP if we > opened the child without discard=unmap or discard=on. But we don't go > through this function when accessing the top node. Move the check down > to bdrv_co_do_pwrite_zeroes() which seems to be used in all code paths. > > This change implements the documented behavior, punching holes only when > opening the image with discard=on or discard=unmap. This may not be the > best default but can improve it later. > > The test depends on a file system supporting discard, deallocating the > entire file when punching hole with the length of the entire file. > Tested with xfs, ext4, and tmpfs. > > [1] https://lists.nongnu.org/archive/html/qemu-discuss/2024-06/msg00003.html > > Signed-off-by: Nir Soffer <nsof...@redhat.com> > --- > block/io.c | 9 +- > tests/qemu-iotests/tests/write-zeroes-unmap | 127 ++++++++++++++++++ > .../qemu-iotests/tests/write-zeroes-unmap.out | 81 +++++++++++ > 3 files changed, 213 insertions(+), 4 deletions(-) > create mode 100755 tests/qemu-iotests/tests/write-zeroes-unmap > create mode 100644 tests/qemu-iotests/tests/write-zeroes-unmap.out
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
signature.asc
Description: PGP signature
