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qcow2: Don't write with BDRV_O_INCOMING

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qcow2_open() causes writes when repairing an image with the dirty flag
set and when clearing autoclear flags. It shouldn't do this when another
qemu instance is still actively working on this image file.

One effect of the bug is that images may have a cleared dirty flag while
the migration source host still has it in use with lazy refcounts
enabled, so refcounts are not accurate and the dirty flag must remain
set.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2014-03-11 15:15:03 +01:00 committed by Stefan Hajnoczi
parent d475e5acd2
commit 27eb6c097c
1 changed files with 7 additions and 5 deletions
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12
block/qcow2.c
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@ -644,7 +644,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
}
/* Clear unknown autoclear feature bits */
if (!bs->read_only && s->autoclear_features != 0) {
if (!bs->read_only && !(flags & BDRV_O_INCOMING) && s->autoclear_features) {
s->autoclear_features = 0;
ret = qcow2_update_header(bs);
if (ret < 0) {
@ -657,7 +657,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
qemu_co_mutex_init(&s->lock);
/* Repair image if dirty */
if (!(flags & BDRV_O_CHECK) && !bs->read_only &&
if (!(flags & (BDRV_O_CHECK | BDRV_O_INCOMING)) && !bs->read_only &&
(s->incompatible_features & QCOW2_INCOMPAT_DIRTY)) {
BdrvCheckResult result = {0};
@ -1137,10 +1137,12 @@ static void qcow2_close(BlockDriverState *bs)
/* else pre-write overlap checks in cache_destroy may crash */
s->l1_table = NULL;
qcow2_cache_flush(bs, s->l2_table_cache);
qcow2_cache_flush(bs, s->refcount_block_cache);
if (!(bs->open_flags & BDRV_O_INCOMING)) {
qcow2_cache_flush(bs, s->l2_table_cache);
qcow2_cache_flush(bs, s->refcount_block_cache);
qcow2_mark_clean(bs);
qcow2_mark_clean(bs);
}
qcow2_cache_destroy(bs, s->l2_table_cache);
qcow2_cache_destroy(bs, s->refcount_block_cache);