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This is not consistent with other drivers and can confuse users or other programs: % qemu-img map --output json "json:{'driver': 'raw', 'file': {'driver':= 'null-co', 'size': '1g'}}" [{ "start": 0, "length": 1073741824, "depth": 0, "present": false, "zer= o": false, "data": false, "compressed": false}] % qemu-nbd "json:{'driver': 'raw', 'file': {'driver': 'null-co', 'size'= : '1g'}}" & % nbdinfo --map nbd://127.0.0.1 0 1073741824 1 hole With this change we report DATA in this case: % ./qemu-img map --output json "json:{'driver': 'raw', 'file': {'driver= ': 'null-co', 'size': '1g'}}" [{ "start": 0, "length": 1073741824, "depth": 0, "present": true, "zero= ": false, "data": true, "compressed": false, "offset": 0}] % ./qemu-nbd "json:{'driver': 'raw', 'file': {'driver': 'null-co', 'siz= e': '1g'}}" & % nbdinfo --map nbd://127.0.0.1 0 1073741824 0 data Signed-off-by: Nir Soffer --- block/null.c | 4 +--- qapi/block-core.json | 5 +++-- 2 files changed, 4 insertions(+), 5 deletions(-) diff --git a/block/null.c b/block/null.c index dc0b1fdbd9..7ba87bd9a9 100644 --- a/block/null.c +++ b/block/null.c @@ -239,9 +239,7 @@ static int coroutine_fn null_co_block_status(BlockDrive= rState *bs, *map =3D offset; *file =3D bs; =20 - if (s->read_zeroes) { - ret |=3D BDRV_BLOCK_ZERO; - } + ret |=3D s->read_zeroes ? BDRV_BLOCK_ZERO : BDRV_BLOCK_DATA; return ret; } =20 diff --git a/qapi/block-core.json b/qapi/block-core.json index b1937780e1..7c95c9e36a 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -3293,8 +3293,9 @@ # requests. Default to zero which completes requests immediately. # (Since 2.4) # -# @read-zeroes: if true, reads from the device produce zeroes; if -# false, the buffer is left unchanged. +# @read-zeroes: if true, emulate a sparse image, and reads from the +# device produce zeroes; if false, emulate an allocated image but +# reads from the device leave the buffer unchanged. # (default: false; since: 4.1) # # Since: 2.9 --=20 2.39.5 (Apple Git-154)