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fallocate(2) says about PUNCH_HOLE: "After a successful call, subsequent reads from this range will return zeros." As it is, PUNCH_HOLE is implemented as a call to blk_pdiscard(), which does not guarantee this. We must call blk_pwrite_zeroes() instead. The difference to ZERO_RANGE is that we pass the `BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK` flags to the call -- the storage is supposed to be unmapped, and a slow fallback by actually writing zeroes as data is not allowed. Closes: https://gitlab.com/qemu-project/qemu/-/issues/1507 Signed-off-by: Hanna Czenczek <hreitz@redhat.com> Message-Id: <20230227104725.33511-2-hreitz@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>