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authorStefan Hajnoczi <stefanha@linux.vnet.ibm.com>2012-06-14 11:42:23 +0100
committerMichael Roth <mdroth@linux.vnet.ibm.com>2012-06-25 08:55:38 -0500
commit0da4c073228c645a0366f3fe801df072cf268482 (patch)
treef7ced80eb0e86284226cdba3131f5a37702426a2
parentPrevent disk data loss when closing qemu (diff)
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qcow2: fix autoclear image header update
The autoclear feature bits can be used for qcow2 file format features that are safe to "drop" by old programs that do not understand the feature. Upon opening the image file unknown autoclear feature bits are cleared and the image file header is rewritten, but this was happening too early in the code when critical header fields were not yet loaded. Process autoclear feature bits after all necessary header information has been loaded. Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com> (cherry picked from commit af7b708db2d03eb47f7ba44a050439ad9ee65e7a) Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
-rw-r--r--block/qcow2.c17
1 files changed, 9 insertions, 8 deletions
diff --git a/block/qcow2.c b/block/qcow2.c
index c2e49cded..79201fce2 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -298,14 +298,6 @@ static int qcow2_open(BlockDriverState *bs, int flags)
goto fail;
}
- if (!bs->read_only && s->autoclear_features != 0) {
- s->autoclear_features = 0;
- ret = qcow2_update_header(bs);
- if (ret < 0) {
- goto fail;
- }
- }
-
/* Check support for various header values */
if (header.refcount_order != 4) {
report_unsupported(bs, "%d bit reference counts",
@@ -411,6 +403,15 @@ static int qcow2_open(BlockDriverState *bs, int flags)
goto fail;
}
+ /* Clear unknown autoclear feature bits */
+ if (!bs->read_only && s->autoclear_features != 0) {
+ s->autoclear_features = 0;
+ ret = qcow2_update_header(bs);
+ if (ret < 0) {
+ goto fail;
+ }
+ }
+
/* Initialise locks */
qemu_co_mutex_init(&s->lock);