On 03.04.20 12:44, Kevin Wolf wrote:
> Calling blk_wait_while_drained() while blk->in_flight is increased for
> the current request is wrong because it will cause the drain operation
> to deadlock.
> 
> Many callers of blk_wait_while_drained() have already increased
> blk->in_flight when called in a blk_aio_*() path, but can also be called
> in synchonous code paths where blk->in_flight isn't increased. This
> means that these calls of blk_wait_while_drained() are wrong at least in
> some cases.
> 
> In order to fix this, increase blk->in_flight even for synchronous
> operations and temporarily decrease the counter again in
> blk_wait_while_drained().
> 
> Fixes: cf3129323f900ef5ddbccbe86e4fa801e88c566e
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/block-backend.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

blk_co_pdiscard() and blk_co_flush() are called from outside of
block-backend.c (namely from mirror.c and nbd/server.c).  Is that OK?

Max