Re: [RFC PATCH] block/io.c: Flush parent for quorum in generic code

[Lukas Straub]

On Wed, 12 May 2021 15:49:57 +0800
Zhang Chen <chen.zhang@intel.com> wrote:

> Fix the issue from this patch:
> [PATCH] block: Flush all children in generic code
> From 883833e29cb800b4d92b5d4736252f4004885191
> 
> Quorum driver do not have the primary child.
> It will caused guest block flush issue when use quorum and NBD.
> The vm guest flushes failed，and then guest filesystem is shutdown.

Hi,
I think the problem is rather that the quorum driver provides
.bdrv_co_flush_to_disk (which predates .bdrv_co_flush) instead of
.bdrv_co_flush. Can you try with the following patch instead?

diff --git a/block/quorum.c b/block/quorum.c
index cfc1436abb..f2c0805000 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -1279,7 +1279,7 @@ static BlockDriver bdrv_quorum = {
     .bdrv_dirname                       = quorum_dirname,
     .bdrv_co_block_status               = quorum_co_block_status,
 
-    .bdrv_co_flush_to_disk              = quorum_co_flush,
+    .bdrv_co_flush                      = quorum_co_flush,
 
     .bdrv_getlength                     = quorum_getlength,


> Signed-off-by: Zhang Chen <chen.zhang@intel.com>
> Reported-by: Minghao Yuan <meeho@qq.com>
> ---
>  block/io.c | 31 ++++++++++++++++++++++---------
>  1 file changed, 22 insertions(+), 9 deletions(-)
> 
> diff --git a/block/io.c b/block/io.c
> index 35b6c56efc..4dc1873cb9 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -2849,6 +2849,13 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
>      BdrvChild *child;
>      int current_gen;
>      int ret = 0;
> +    bool no_primary_child = false;
> +
> +    /* Quorum drivers do not have the primary child. */
> +    if (!primary_child) {
> +        primary_child = bs->file;
> +        no_primary_child = true;
> +    }
>  
>      bdrv_inc_in_flight(bs);
>  
> @@ -2886,12 +2893,12 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
>  
>      /* But don't actually force it to the disk with cache=unsafe */
>      if (bs->open_flags & BDRV_O_NO_FLUSH) {
> -        goto flush_children;
> +        goto flush_data;
>      }
>  
>      /* Check if we really need to flush anything */
>      if (bs->flushed_gen == current_gen) {
> -        goto flush_children;
> +        goto flush_data;
>      }
>  
>      BLKDBG_EVENT(primary_child, BLKDBG_FLUSH_TO_DISK);
> @@ -2938,13 +2945,19 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
>      /* Now flush the underlying protocol.  It will also have BDRV_O_NO_FLUSH
>       * in the case of cache=unsafe, so there are no useless flushes.
>       */
> -flush_children:
> -    ret = 0;
> -    QLIST_FOREACH(child, &bs->children, next) {
> -        if (child->perm & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED)) {
> -            int this_child_ret = bdrv_co_flush(child->bs);
> -            if (!ret) {
> -                ret = this_child_ret;
> +flush_data:
> +    if (no_primary_child) {
> +        /* Flush parent */
> +        ret = bs->file ? bdrv_co_flush(bs->file->bs) : 0;
> +    } else {
> +        /* Flush childrens */
> +        ret = 0;
> +        QLIST_FOREACH(child, &bs->children, next) {
> +            if (child->perm & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED)) {
> +                int this_child_ret = bdrv_co_flush(child->bs);
> +                if (!ret) {
> +                    ret = this_child_ret;
> +                }
>              }
>          }
>      }



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