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authorEric Blake <eblake@redhat.com>2019-09-16 21:39:17 -0500
committerEric Blake <eblake@redhat.com>2019-09-24 07:30:19 -0500
commit61bc846d8c58535af6884b637a4005dd6111ea95 (patch)
treea5c98306bdac3b6311aa472745ec81879a3cbdb2 /nbd
parentb4961249af0403fa55aae57c4c8806b24f7a7b33 (diff)
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nbd: Grab aio context lock in more places
When iothreads are in use, the failure to grab the aio context results in an assertion failure when trying to unlock things during blk_unref, when trying to unlock a mutex that was not locked. In short, all calls to nbd_export_put need to done while within the correct aio context. But since nbd_export_put can recursively reach itself via nbd_export_close, and recursively grabbing the context would deadlock, we can't do the context grab directly in those functions, but must do so in their callers. Hoist the use of the correct aio_context from nbd_export_new() to its caller qmp_nbd_server_add(). Then tweak qmp_nbd_server_remove(), nbd_eject_notifier(), and nbd_esport_close_all() to grab the right context, so that all callers during qemu now own the context before nbd_export_put() can call blk_unref(). Remaining uses in qemu-nbd don't matter (since that use case does not support iothreads). Suggested-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20190917023917.32226-1-eblake@redhat.com> Reviewed-by: Sergio Lopez <slp@redhat.com>
Diffstat (limited to 'nbd')
-rw-r--r--nbd/server.c22
1 files changed, 18 insertions, 4 deletions
diff --git a/nbd/server.c b/nbd/server.c
index 31d624e..d8d1e62 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1461,7 +1461,12 @@ static void blk_aio_detach(void *opaque)
static void nbd_eject_notifier(Notifier *n, void *data)
{
NBDExport *exp = container_of(n, NBDExport, eject_notifier);
+ AioContext *aio_context;
+
+ aio_context = exp->ctx;
+ aio_context_acquire(aio_context);
nbd_export_close(exp);
+ aio_context_release(aio_context);
}
NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
@@ -1480,12 +1485,11 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
* NBD exports are used for non-shared storage migration. Make sure
* that BDRV_O_INACTIVE is cleared and the image is ready for write
* access since the export could be available before migration handover.
+ * ctx was acquired in the caller.
*/
assert(name);
ctx = bdrv_get_aio_context(bs);
- aio_context_acquire(ctx);
bdrv_invalidate_cache(bs, NULL);
- aio_context_release(ctx);
/* Don't allow resize while the NBD server is running, otherwise we don't
* care what happens with the node. */
@@ -1493,7 +1497,7 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
if (!readonly) {
perm |= BLK_PERM_WRITE;
}
- blk = blk_new(bdrv_get_aio_context(bs), perm,
+ blk = blk_new(ctx, perm,
BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
BLK_PERM_WRITE | BLK_PERM_GRAPH_MOD);
ret = blk_insert_bs(blk, bs, errp);
@@ -1560,7 +1564,7 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
}
exp->close = close;
- exp->ctx = blk_get_aio_context(blk);
+ exp->ctx = ctx;
blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
if (on_eject_blk) {
@@ -1593,6 +1597,12 @@ NBDExport *nbd_export_find(const char *name)
return NULL;
}
+AioContext *
+nbd_export_aio_context(NBDExport *exp)
+{
+ return exp->ctx;
+}
+
void nbd_export_close(NBDExport *exp)
{
NBDClient *client, *next;
@@ -1687,9 +1697,13 @@ BlockBackend *nbd_export_get_blockdev(NBDExport *exp)
void nbd_export_close_all(void)
{
NBDExport *exp, *next;
+ AioContext *aio_context;
QTAILQ_FOREACH_SAFE(exp, &exports, next, next) {
+ aio_context = exp->ctx;
+ aio_context_acquire(aio_context);
nbd_export_close(exp);
+ aio_context_release(aio_context);
}
}