From: Alberto Garcia <berto@igalia.com>
To: qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>,
Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
Alberto Garcia <berto@igalia.com>,
qemu-block@nongnu.org, Max Reitz <mreitz@redhat.com>
Subject: [PATCH v5 1/2] qcow2: Report BDRV_BLOCK_ZERO more accurately in bdrv_co_block_status()
Date: Mon, 26 Oct 2020 17:58:26 +0100 [thread overview]
Message-ID: <66fa0914a0e2b727ab6d1b63ca773d7cd29a9a9e.1603731354.git.berto@igalia.com> (raw)
In-Reply-To: <cover.1603731354.git.berto@igalia.com>
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 02528b3823..6fe1b275b6 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2282,17 +2282,17 @@ 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;
}
}
--
2.20.1
next prev parent reply other threads:[~2020-10-26 17:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-26 16:58 [PATCH v5 0/2] Skip copy-on-write when allocating a zero cluster Alberto Garcia
2020-10-26 16:58 ` Alberto Garcia [this message]
2020-10-26 16:58 ` [PATCH v5 2/2] qcow2: " Alberto Garcia
2020-10-27 11:07 ` [PATCH v5 0/2] " Kevin Wolf
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