| Message ID | e12fc2535199ce30c2674132dd62716bbd6359b3.1600698425.git.berto@igalia.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Skip copy-on-write when allocating a zero cluster | expand |
21.09.2020 17:30, 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 a2389bb38c..ef1ea806e8 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -2391,17 +2391,17 @@ 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) { > + } else if (bs->drv->supports_backing) { > BlockDriverState *cow_bs = bdrv_cow_bs(bs); > > - if (cow_bs) { > + if (!cow_bs) { > + ret |= BDRV_BLOCK_ZERO; > + } else if (want_zero) { > int64_t size2 = bdrv_getlength(cow_bs); > > if (size2 >= 0 && offset >= size2) { > ret |= BDRV_BLOCK_ZERO; > } > - } else { > - ret |= BDRV_BLOCK_ZERO; > } > } > > -- Best regards, Vladimir
diff --git a/block/io.c b/block/io.c index a2389bb38c..ef1ea806e8 100644 --- a/block/io.c +++ b/block/io.c @@ -2391,17 +2391,17 @@ 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) { + } else if (bs->drv->supports_backing) { BlockDriverState *cow_bs = bdrv_cow_bs(bs); - if (cow_bs) { + if (!cow_bs) { + ret |= BDRV_BLOCK_ZERO; + } else if (want_zero) { int64_t size2 = bdrv_getlength(cow_bs); 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(-)