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[PULL 3/4] block: Skip COR for inactive nodes
From: |
Stefan Hajnoczi |
Subject: |
[PULL 3/4] block: Skip COR for inactive nodes |
Date: |
Tue, 8 Oct 2019 15:55:04 +0100 |
From: Max Reitz <address@hidden>
We must not write data to inactive nodes, and a COR is certainly
something we can simply not do without upsetting anyone. So skip COR
operations on inactive nodes.
Signed-off-by: Max Reitz <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Message-id: address@hidden
Message-Id: <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
block/io.c | 41 +++++++++++++++++++++++++++--------------
1 file changed, 27 insertions(+), 14 deletions(-)
diff --git a/block/io.c b/block/io.c
index f8c3596131..4f9ee97c2b 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1246,11 +1246,18 @@ static int coroutine_fn
bdrv_co_do_copy_on_readv(BdrvChild *child,
int max_transfer = MIN_NON_ZERO(bs->bl.max_transfer,
BDRV_REQUEST_MAX_BYTES);
unsigned int progress = 0;
+ bool skip_write;
if (!drv) {
return -ENOMEDIUM;
}
+ /*
+ * Do not write anything when the BDS is inactive. That is not
+ * allowed, and it would not help.
+ */
+ skip_write = (bs->open_flags & BDRV_O_INACTIVE);
+
/* FIXME We cannot require callers to have write permissions when all they
* are doing is a read request. If we did things right, write permissions
* would be obtained anyway, but internally by the copy-on-read code. As
@@ -1274,23 +1281,29 @@ static int coroutine_fn
bdrv_co_do_copy_on_readv(BdrvChild *child,
while (cluster_bytes) {
int64_t pnum;
- ret = bdrv_is_allocated(bs, cluster_offset,
- MIN(cluster_bytes, max_transfer), &pnum);
- if (ret < 0) {
- /* Safe to treat errors in querying allocation as if
- * unallocated; we'll probably fail again soon on the
- * read, but at least that will set a decent errno.
- */
+ if (skip_write) {
+ ret = 1; /* "already allocated", so nothing will be copied */
pnum = MIN(cluster_bytes, max_transfer);
- }
+ } else {
+ ret = bdrv_is_allocated(bs, cluster_offset,
+ MIN(cluster_bytes, max_transfer), &pnum);
+ if (ret < 0) {
+ /*
+ * Safe to treat errors in querying allocation as if
+ * unallocated; we'll probably fail again soon on the
+ * read, but at least that will set a decent errno.
+ */
+ pnum = MIN(cluster_bytes, max_transfer);
+ }
- /* Stop at EOF if the image ends in the middle of the cluster */
- if (ret == 0 && pnum == 0) {
- assert(progress >= bytes);
- break;
- }
+ /* Stop at EOF if the image ends in the middle of the cluster */
+ if (ret == 0 && pnum == 0) {
+ assert(progress >= bytes);
+ break;
+ }
- assert(skip_bytes < pnum);
+ assert(skip_bytes < pnum);
+ }
if (ret <= 0) {
QEMUIOVector local_qiov;
--
2.21.0