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authorMax Reitz <mreitz@redhat.com>2016-01-29 16:36:14 +0100
committerMax Reitz <mreitz@redhat.com>2016-02-02 17:50:46 +0100
commitca9bd24cf1d53775169ba9adc17e265554d1afed (patch)
treec8eda481f153bb8086cc2f59642564943efa136b /block.c
parentd8da3cef3bc649492d190e029343293df1386027 (diff)
downloadqemu-arm-ca9bd24cf1d53775169ba9adc17e265554d1afed.tar.gz
block: Rewrite bdrv_close_all()
This patch rewrites bdrv_close_all(): Until now, all root BDSs have been force-closed. This is bad because it can lead to cached data not being flushed to disk. Instead, try to make all reference holders relinquish their reference voluntarily: 1. All BlockBackend users are handled by making all BBs simply eject their BDS tree. Since a BDS can never be on top of a BB, this will not cause any of the issues as seen with the force-closing of BDSs. The references will be relinquished and any further access to the BB will fail gracefully. 2. All BDSs which are owned by the monitor itself (because they do not have a BB) are relinquished next. 3. Besides BBs and the monitor, block jobs and other BDSs are the only things left that can hold a reference to BDSs. After every remaining block job has been canceled, there should not be any BDSs left (and the loop added here will always terminate (as long as NDEBUG is not defined), because either all_bdrv_states will be empty or there will not be any block job left to cancel, failing the assertion). Signed-off-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c34
1 files changed, 26 insertions, 8 deletions
diff --git a/block.c b/block.c
index d687d2c2b6..ff1aafc85f 100644
--- a/block.c
+++ b/block.c
@@ -2145,9 +2145,7 @@ static void bdrv_close(BlockDriverState *bs)
{
BdrvAioNotifier *ban, *ban_next;
- if (bs->job) {
- block_job_cancel_sync(bs->job);
- }
+ assert(!bs->job);
/* Disable I/O limits and drain all pending throttled requests */
if (bs->throttle_state) {
@@ -2214,13 +2212,33 @@ static void bdrv_close(BlockDriverState *bs)
void bdrv_close_all(void)
{
BlockDriverState *bs;
+ AioContext *aio_context;
- QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
- AioContext *aio_context = bdrv_get_aio_context(bs);
+ /* Drop references from requests still in flight, such as canceled block
+ * jobs whose AIO context has not been polled yet */
+ bdrv_drain_all();
- aio_context_acquire(aio_context);
- bdrv_close(bs);
- aio_context_release(aio_context);
+ blk_remove_all_bs();
+ blockdev_close_all_bdrv_states();
+
+ /* Cancel all block jobs */
+ while (!QTAILQ_EMPTY(&all_bdrv_states)) {
+ QTAILQ_FOREACH(bs, &all_bdrv_states, bs_list) {
+ aio_context = bdrv_get_aio_context(bs);
+
+ aio_context_acquire(aio_context);
+ if (bs->job) {
+ block_job_cancel_sync(bs->job);
+ aio_context_release(aio_context);
+ break;
+ }
+ aio_context_release(aio_context);
+ }
+
+ /* All the remaining BlockDriverStates are referenced directly or
+ * indirectly from block jobs, so there needs to be at least one BDS
+ * directly used by a block job */
+ assert(bs);
}
}