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authorKevin Wolf <kwolf@redhat.com>2019-04-17 17:15:25 +0200
committerKevin Wolf <kwolf@redhat.com>2019-04-30 15:29:00 +0200
commit1bffe1ae7a7b707c3a14ea2ccd00d3609d3ce4d8 (patch)
tree90876b4809d9363b359baf857cb8adeda0f5964a
parent36b9986b08787019ef42f985b4002e275275a135 (diff)
block: Fix AioContext switch for bs->drv == NULL
Even for block nodes with bs->drv == NULL, we can't just ignore a bdrv_set_aio_context() call. Leaving the node in its old context can mean that it's still in an iothread context in bdrv_close_all() during shutdown, resulting in an attempted unlock of the AioContext lock which we don't hold. This is an example stack trace of a related crash: #0 0x00007ffff59da57f in raise () at /lib64/libc.so.6 #1 0x00007ffff59c4895 in abort () at /lib64/libc.so.6 #2 0x0000555555b97b1e in error_exit (err=<optimized out>, msg=msg@entry=0x555555d386d0 <__func__.19059> "qemu_mutex_unlock_impl") at util/qemu-thread-posix.c:36 #3 0x0000555555b97f7f in qemu_mutex_unlock_impl (mutex=mutex@entry=0x5555568002f0, file=file@entry=0x555555d378df "util/async.c", line=line@entry=507) at util/qemu-thread-posix.c:97 #4 0x0000555555b92f55 in aio_context_release (ctx=ctx@entry=0x555556800290) at util/async.c:507 #5 0x0000555555b05cf8 in bdrv_prwv_co (child=child@entry=0x7fffc80012f0, offset=offset@entry=131072, qiov=qiov@entry=0x7fffffffd4f0, is_write=is_write@entry=true, flags=flags@entry=0) at block/io.c:833 #6 0x0000555555b060a9 in bdrv_pwritev (qiov=0x7fffffffd4f0, offset=131072, child=0x7fffc80012f0) at block/io.c:990 #7 0x0000555555b060a9 in bdrv_pwrite (child=0x7fffc80012f0, offset=131072, buf=<optimized out>, bytes=<optimized out>) at block/io.c:990 #8 0x0000555555ae172b in qcow2_cache_entry_flush (bs=bs@entry=0x555556810680, c=c@entry=0x5555568cc740, i=i@entry=0) at block/qcow2-cache.c:51 #9 0x0000555555ae18dd in qcow2_cache_write (bs=bs@entry=0x555556810680, c=0x5555568cc740) at block/qcow2-cache.c:248 #10 0x0000555555ae15de in qcow2_cache_flush (bs=0x555556810680, c=<optimized out>) at block/qcow2-cache.c:259 #11 0x0000555555ae16b1 in qcow2_cache_flush_dependency (c=0x5555568a1700, c=0x5555568a1700, bs=0x555556810680) at block/qcow2-cache.c:194 #12 0x0000555555ae16b1 in qcow2_cache_entry_flush (bs=bs@entry=0x555556810680, c=c@entry=0x5555568a1700, i=i@entry=0) at block/qcow2-cache.c:194 #13 0x0000555555ae18dd in qcow2_cache_write (bs=bs@entry=0x555556810680, c=0x5555568a1700) at block/qcow2-cache.c:248 #14 0x0000555555ae15de in qcow2_cache_flush (bs=bs@entry=0x555556810680, c=<optimized out>) at block/qcow2-cache.c:259 #15 0x0000555555ad242c in qcow2_inactivate (bs=bs@entry=0x555556810680) at block/qcow2.c:2124 #16 0x0000555555ad2590 in qcow2_close (bs=0x555556810680) at block/qcow2.c:2153 #17 0x0000555555ab0c62 in bdrv_close (bs=0x555556810680) at block.c:3358 #18 0x0000555555ab0c62 in bdrv_delete (bs=0x555556810680) at block.c:3542 #19 0x0000555555ab0c62 in bdrv_unref (bs=0x555556810680) at block.c:4598 #20 0x0000555555af4d72 in blk_remove_bs (blk=blk@entry=0x5555568103d0) at block/block-backend.c:785 #21 0x0000555555af4dbb in blk_remove_all_bs () at block/block-backend.c:483 #22 0x0000555555aae02f in bdrv_close_all () at block.c:3412 #23 0x00005555557f9796 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4776 The reproducer I used is a qcow2 image on gluster volume, where the virtual disk size (4 GB) is larger than the gluster volume size (64M), so we can easily trigger an ENOSPC. This backend is assigned to a virtio-blk device using an iothread, and then from the guest a 'dd if=/dev/zero of=/dev/vda bs=1G count=1' causes the VM to stop because of an I/O error. qemu_gluster_co_flush_to_disk() sets bs->drv = NULL on error, so when virtio-blk stops the dataplane, the block nodes stay in the iothread AioContext. A 'quit' monitor command issued from this paused state crashes the process. Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1631227 Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
-rw-r--r--block.c12
1 files changed, 2 insertions, 10 deletions
diff --git a/block.c b/block.c
index 16615bc876..9ae5c0ed2f 100644
--- a/block.c
+++ b/block.c
@@ -5672,10 +5672,6 @@ void bdrv_detach_aio_context(BlockDriverState *bs)
BdrvAioNotifier *baf, *baf_tmp;
BdrvChild *child;
- if (!bs->drv) {
- return;
- }
-
assert(!bs->walking_aio_notifiers);
bs->walking_aio_notifiers = true;
QLIST_FOREACH_SAFE(baf, &bs->aio_notifiers, list, baf_tmp) {
@@ -5690,7 +5686,7 @@ void bdrv_detach_aio_context(BlockDriverState *bs)
*/
bs->walking_aio_notifiers = false;
- if (bs->drv->bdrv_detach_aio_context) {
+ if (bs->drv && bs->drv->bdrv_detach_aio_context) {
bs->drv->bdrv_detach_aio_context(bs);
}
QLIST_FOREACH(child, &bs->children, next) {
@@ -5709,10 +5705,6 @@ void bdrv_attach_aio_context(BlockDriverState *bs,
BdrvAioNotifier *ban, *ban_tmp;
BdrvChild *child;
- if (!bs->drv) {
- return;
- }
-
if (bs->quiesce_counter) {
aio_disable_external(new_context);
}
@@ -5722,7 +5714,7 @@ void bdrv_attach_aio_context(BlockDriverState *bs,
QLIST_FOREACH(child, &bs->children, next) {
bdrv_attach_aio_context(child->bs, new_context);
}
- if (bs->drv->bdrv_attach_aio_context) {
+ if (bs->drv && bs->drv->bdrv_attach_aio_context) {
bs->drv->bdrv_attach_aio_context(bs, new_context);
}