[Qemu-devel] [PATCH] block: Avoid bogus flags during mirroring

[Eric Blake <eblake@redhat.com>]

Commit e253f4b8 converted mirroring from sector-based bdrv_aio_*
to byte-based blk_aio_*, but failed to account for the subtle
difference in signatures (the former takes a semi-redundant length,
the latter takes a flags parameter).  Since all of our flags are
currently smaller in size than BDRV_SECTOR_SIZE, it has no ill
effects until we either perform sub-sector mirroring, or we start
asserting that no unexpected flags are set.  I found it while
testing new asserts when qemu-iotests 132 started warning about an
unknown flag 0x200000.

Add an assert to help us catch any other improper flags.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 block/block-backend.c | 2 ++
 block/mirror.c        | 6 ++----
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index 34500e6..a5dc6e3 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -945,6 +945,8 @@ static BlockAIOCB *blk_aio_prwv(BlockBackend *blk, int64_t offset, int bytes,
     acb->bh = NULL;
     acb->has_returned = false;

+    assert(flags <= 0x1f);
+
     co = qemu_coroutine_create(co_entry);
     qemu_coroutine_enter(co, acb);

diff --git a/block/mirror.c b/block/mirror.c
index fbbc496..41848b2 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -157,8 +157,7 @@ static void mirror_read_complete(void *opaque, int ret)
         return;
     }
     blk_aio_pwritev(s->target, op->sector_num * BDRV_SECTOR_SIZE, &op->qiov,
-                    op->nb_sectors * BDRV_SECTOR_SIZE,
-                    mirror_write_complete, op);
+                    0, mirror_write_complete, op);
 }

 static inline void mirror_clip_sectors(MirrorBlockJob *s,
@@ -275,8 +274,7 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num,
     s->sectors_in_flight += nb_sectors;
     trace_mirror_one_iteration(s, sector_num, nb_sectors);

-    blk_aio_preadv(source, sector_num * BDRV_SECTOR_SIZE, &op->qiov,
-                   nb_sectors * BDRV_SECTOR_SIZE,
+    blk_aio_preadv(source, sector_num * BDRV_SECTOR_SIZE, &op->qiov, 0,
                    mirror_read_complete, op);
     return ret;
 }
-- 
2.5.5