block: acquire AioContext in bdrv_*_all()

bdrv_close_all(), bdrv_commit_all(), bdrv_flush_all(),
bdrv_invalidate_cache_all(), and bdrv_clear_incoming_migration_all() are
called by main loop code and touch all BlockDriverState instances.

Some BlockDriverState instances may be running in another AioContext.
Make sure to acquire the AioContext before closing the BlockDriverState.

This will protect against race conditions once virtio-blk data-plane is
using the BlockDriverState from another AioContext event loop.

Note that this patch does not convert bdrv_drain_all() yet since that
conversion is non-trivial.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/block.c b/block.c
index 05ec8e13e49c88814c99d0fb09b754267b206eac..7cccb84dab96e2eca562cc1ad1f06ba878db60e8 100644 (file)
--- a/block.c
+++ b/block.c
@@ -1856,7 +1856,11 @@ void bdrv_close_all(void)
     BlockDriverState *bs;
 
     QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(aio_context);
         bdrv_close(bs);
+        aio_context_release(aio_context);
     }
 }
 
@@ -2352,12 +2356,17 @@ int bdrv_commit_all(void)
     BlockDriverState *bs;
 
     QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(aio_context);
         if (bs->drv && bs->backing_hd) {
             int ret = bdrv_commit(bs);
             if (ret < 0) {
+                aio_context_release(aio_context);
                 return ret;
             }
         }
+        aio_context_release(aio_context);
     }
     return 0;
 }
@@ -3833,10 +3842,15 @@ int bdrv_flush_all(void)
     int result = 0;
 
     QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
-        int ret = bdrv_flush(bs);
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+        int ret;
+
+        aio_context_acquire(aio_context);
+        ret = bdrv_flush(bs);
         if (ret < 0 && !result) {
             result = ret;
         }
+        aio_context_release(aio_context);
     }
 
     return result;
@@ -4982,7 +4996,11 @@ void bdrv_invalidate_cache_all(Error **errp)
     Error *local_err = NULL;
 
     QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(aio_context);
         bdrv_invalidate_cache(bs, &local_err);
+        aio_context_release(aio_context);
         if (local_err) {
             error_propagate(errp, local_err);
             return;
@@ -4995,7 +5013,11 @@ void bdrv_clear_incoming_migration_all(void)
     BlockDriverState *bs;
 
     QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(aio_context);
         bs->open_flags = bs->open_flags & ~(BDRV_O_INCOMING);
+        aio_context_release(aio_context);
     }
 }