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[PULL 2/9] block: nbd: Fix convert qcow2 compressed to nbd
From: |
Eric Blake |
Subject: |
[PULL 2/9] block: nbd: Fix convert qcow2 compressed to nbd |
Date: |
Tue, 28 Jul 2020 10:04:00 -0500 |
From: Nir Soffer <nirsof@gmail.com>
When converting to qcow2 compressed format, the last step is a special
zero length compressed write, ending in a call to bdrv_co_truncate(). This
call always fails for the nbd driver since it does not implement
bdrv_co_truncate().
For block devices, which have the same limits, the call succeeds since
the file driver implements bdrv_co_truncate(). If the caller asked to
truncate to the same or smaller size with exact=false, the truncate
succeeds. Implement the same logic for nbd.
Example failing without this change:
In one shell start qemu-nbd:
$ truncate -s 1g test.tar
$ qemu-nbd --socket=/tmp/nbd.sock --persistent --format=raw --offset 1536
test.tar
In another shell convert an image to qcow2 compressed via NBD:
$ echo "disk data" > disk.raw
$ truncate -s 1g disk.raw
$ qemu-img convert -f raw -O qcow2 -c disk1.raw
nbd+unix:///?socket=/tmp/nbd.sock; echo $?
1
qemu-img failed, but the conversion was successful:
$ qemu-img info nbd+unix:///?socket=/tmp/nbd.sock
image: nbd+unix://?socket=/tmp/nbd.sock
file format: qcow2
virtual size: 1 GiB (1073741824 bytes)
...
$ qemu-img check nbd+unix:///?socket=/tmp/nbd.sock
No errors were found on the image.
1/16384 = 0.01% allocated, 100.00% fragmented, 100.00% compressed clusters
Image end offset: 393216
$ qemu-img compare disk.raw nbd+unix:///?socket=/tmp/nbd.sock
Images are identical.
Fixes: https://bugzilla.redhat.com/1860627
Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Message-Id: <20200727215846.395443-2-nsoffer@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: typo fixes]
Signed-off-by: Eric Blake <eblake@redhat.com>
---
block/nbd.c | 30 ++++++++++++++++++++++++++++++
qemu-io-cmds.c | 2 +-
2 files changed, 31 insertions(+), 1 deletion(-)
diff --git a/block/nbd.c b/block/nbd.c
index 65a4f56924ec..8934bcb47901 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -1966,6 +1966,33 @@ static void nbd_close(BlockDriverState *bs)
nbd_clear_bdrvstate(s);
}
+/*
+ * NBD cannot truncate, but if the caller asks to truncate to the same size, or
+ * to a smaller size with exact=false, there is no reason to fail the
+ * operation.
+ *
+ * Preallocation mode is ignored since it does not seems useful to fail when
+ * we never change anything.
+ */
+static int coroutine_fn nbd_co_truncate(BlockDriverState *bs, int64_t offset,
+ bool exact, PreallocMode prealloc,
+ BdrvRequestFlags flags, Error **errp)
+{
+ BDRVNBDState *s = bs->opaque;
+
+ if (offset != s->info.size && exact) {
+ error_setg(errp, "Cannot resize NBD nodes");
+ return -ENOTSUP;
+ }
+
+ if (offset > s->info.size) {
+ error_setg(errp, "Cannot grow NBD nodes");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int64_t nbd_getlength(BlockDriverState *bs)
{
BDRVNBDState *s = bs->opaque;
@@ -2045,6 +2072,7 @@ static BlockDriver bdrv_nbd = {
.bdrv_co_flush_to_os = nbd_co_flush,
.bdrv_co_pdiscard = nbd_client_co_pdiscard,
.bdrv_refresh_limits = nbd_refresh_limits,
+ .bdrv_co_truncate = nbd_co_truncate,
.bdrv_getlength = nbd_getlength,
.bdrv_detach_aio_context = nbd_client_detach_aio_context,
.bdrv_attach_aio_context = nbd_client_attach_aio_context,
@@ -2072,6 +2100,7 @@ static BlockDriver bdrv_nbd_tcp = {
.bdrv_co_flush_to_os = nbd_co_flush,
.bdrv_co_pdiscard = nbd_client_co_pdiscard,
.bdrv_refresh_limits = nbd_refresh_limits,
+ .bdrv_co_truncate = nbd_co_truncate,
.bdrv_getlength = nbd_getlength,
.bdrv_detach_aio_context = nbd_client_detach_aio_context,
.bdrv_attach_aio_context = nbd_client_attach_aio_context,
@@ -2099,6 +2128,7 @@ static BlockDriver bdrv_nbd_unix = {
.bdrv_co_flush_to_os = nbd_co_flush,
.bdrv_co_pdiscard = nbd_client_co_pdiscard,
.bdrv_refresh_limits = nbd_refresh_limits,
+ .bdrv_co_truncate = nbd_co_truncate,
.bdrv_getlength = nbd_getlength,
.bdrv_detach_aio_context = nbd_client_detach_aio_context,
.bdrv_attach_aio_context = nbd_client_attach_aio_context,
diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 851f07e8f8b9..baeae86d8c85 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -1715,7 +1715,7 @@ static int truncate_f(BlockBackend *blk, int argc, char
**argv)
* exact=true. It is better to err on the "emit more errors" side
* than to be overly permissive.
*/
- ret = blk_truncate(blk, offset, true, PREALLOC_MODE_OFF, 0, &local_err);
+ ret = blk_truncate(blk, offset, false, PREALLOC_MODE_OFF, 0, &local_err);
if (ret < 0) {
error_report_err(local_err);
return ret;
--
2.27.0
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