From 38841dcd27a41e2d8916b7cf4f508a5663f453ff Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Wed, 24 Jul 2019 19:12:34 +0200 Subject: [PATCH] qcow2: Fix .bdrv_has_zero_init() If a qcow2 file is preallocated, it can no longer guarantee that it initially appears as filled with zeroes. So implement .bdrv_has_zero_init() by checking whether the file is preallocated; if so, forward the call to the underlying storage node, except for when it is encrypted: Encrypted preallocated images always return effectively random data, so .bdrv_has_zero_init() must always return 0 for them. .bdrv_has_zero_init_truncate() can remain bdrv_has_zero_init_1(), because it presupposes PREALLOC_MODE_OFF. Reported-by: Stefano Garzarella Signed-off-by: Max Reitz Message-id: 20190724171239.8764-7-mreitz@redhat.com Reviewed-by: Maxim Levitsky Signed-off-by: Max Reitz --- block/qcow2.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/block/qcow2.c b/block/qcow2.c index ea3b42fdac..7c5a4859f7 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -4632,6 +4632,33 @@ static ImageInfoSpecific *qcow2_get_specific_info(BlockDriverState *bs, return spec_info; } +static int qcow2_has_zero_init(BlockDriverState *bs) +{ + BDRVQcow2State *s = bs->opaque; + bool preallocated; + + if (qemu_in_coroutine()) { + qemu_co_mutex_lock(&s->lock); + } + /* + * Check preallocation status: Preallocated images have all L2 + * tables allocated, nonpreallocated images have none. It is + * therefore enough to check the first one. + */ + preallocated = s->l1_size > 0 && s->l1_table[0] != 0; + if (qemu_in_coroutine()) { + qemu_co_mutex_unlock(&s->lock); + } + + if (!preallocated) { + return 1; + } else if (bs->encrypted) { + return 0; + } else { + return bdrv_has_zero_init(s->data_file->bs); + } +} + static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos) { @@ -5187,7 +5214,7 @@ BlockDriver bdrv_qcow2 = { .bdrv_child_perm = bdrv_format_default_perms, .bdrv_co_create_opts = qcow2_co_create_opts, .bdrv_co_create = qcow2_co_create, - .bdrv_has_zero_init = bdrv_has_zero_init_1, + .bdrv_has_zero_init = qcow2_has_zero_init, .bdrv_has_zero_init_truncate = bdrv_has_zero_init_1, .bdrv_co_block_status = qcow2_co_block_status, -- 2.11.0