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block: Use BDRV_O_NO_BACKING where appropriate 

If you open an image temporarily just because you want to check its size
or get it flushed, there's no real reason to open the whole backing file
chain.

This is a backport of c9fbb99d41 to
qemu 1.7.1.

The backport was done to fix a bug where QEMU 1.7.1 would crash or freeze
when the user take around 80 consecutives snapshots in a row.

git bisect would lead to commit: ba2ab2f2ca
and it was clear that BDRV_NO_BACKING was missing.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
This commit is contained in:
Kevin Wolf 2014-04-18 15:44:19 +02:00 committed by Michael Roth
parent 792a40384f
commit b1a86eb532
3 changed files with 5 additions and 4 deletions
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4
block.c
View File

@ -1067,9 +1067,9 @@ int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
/* if snapshot, we create a temporary backing file and open it
instead of opening 'filename' directly */
/* if there is a backing file, use it */
bs1 = bdrv_new("");
ret = bdrv_open(bs1, filename, NULL, 0, drv, &local_err);
ret = bdrv_open(bs1, filename, NULL, BDRV_O_NO_BACKING, drv,
&local_err);
if (ret < 0) {
bdrv_unref(bs1);
goto fail;

3
block/qcow2.c
View File

@ -1605,7 +1605,8 @@ static int qcow2_create2(const char *filename, int64_t total_size,
/* Reopen the image without BDRV_O_NO_FLUSH to flush it before returning */
ret = bdrv_open(bs, filename, NULL,
BDRV_O_RDWR | BDRV_O_CACHE_WB, drv, &local_err);
BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_BACKING,
drv, &local_err);
if (error_is_set(&local_err)) {
error_propagate(errp, local_err);
goto out;

2
block/vmdk.c
View File

@ -1689,7 +1689,7 @@ static int vmdk_create(const char *filename, QEMUOptionParameter *options,
}
if (backing_file) {
BlockDriverState *bs = bdrv_new("");
ret = bdrv_open(bs, backing_file, NULL, 0, NULL, errp);
ret = bdrv_open(bs, backing_file, NULL, BDRV_O_NO_BACKING, NULL, errp);
if (ret != 0) {
bdrv_unref(bs);
return ret;