| Message ID | 104cbe2dfac940e4c5ca0a7e2eb22a0245e206f7.1599759873.git.berto@igalia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Skip copy-on-write when allocating a zero cluster | expand |
10.09.2020 20:46, Alberto Garcia wrote: > If a BlockDriverState supports backing files but has none then any > unallocated area reads back as zeroes. > > bdrv_co_block_status() is only reporting this is if want_zero is true, > but this is an inexpensive test and there is no reason not to do it in > all cases. > > Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> > Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> > --- > block/io.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/block/io.c b/block/io.c > index ad3a51ed53..1b0ae29610 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -2408,16 +2408,16 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs, > > if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) { > ret |= BDRV_BLOCK_ALLOCATED; > - } else if (want_zero && bs->drv->supports_backing) { > - if (bs->backing) { > + } else if (bs->drv->supports_backing) { > + if (!bs->backing) { > + ret |= BDRV_BLOCK_ZERO; > + } else if (want_zero) { > BlockDriverState *bs2 = bs->backing->bs; > int64_t size2 = bdrv_getlength(bs2); > > if (size2 >= 0 && offset >= size2) { > ret |= BDRV_BLOCK_ZERO; > } > - } else { > - ret |= BDRV_BLOCK_ZERO; > } > } > >
diff --git a/block/io.c b/block/io.c index ad3a51ed53..1b0ae29610 100644 --- a/block/io.c +++ b/block/io.c @@ -2408,16 +2408,16 @@ static int coroutine_fn bdrv_co_block_status(BlockDriverState *bs, if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) { ret |= BDRV_BLOCK_ALLOCATED; - } else if (want_zero && bs->drv->supports_backing) { - if (bs->backing) { + } else if (bs->drv->supports_backing) { + if (!bs->backing) { + ret |= BDRV_BLOCK_ZERO; + } else if (want_zero) { BlockDriverState *bs2 = bs->backing->bs; int64_t size2 = bdrv_getlength(bs2); if (size2 >= 0 && offset >= size2) { ret |= BDRV_BLOCK_ZERO; } - } else { - ret |= BDRV_BLOCK_ZERO; } }
If a BlockDriverState supports backing files but has none then any unallocated area reads back as zeroes. bdrv_co_block_status() is only reporting this is if want_zero is true, but this is an inexpensive test and there is no reason not to do it in all cases. Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Signed-off-by: Alberto Garcia <berto@igalia.com> --- block/io.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)