Commit db0289b9 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

block: Make bdrv_drain_invoke() recursive 



This change separates bdrv_drain_invoke(), which calls the BlockDriver
drain callbacks, from bdrv_drain_recurse(). Instead, the function
performs its own recursion now.

One reason for this is that bdrv_drain_recurse() can be called multiple
times by bdrv_drain_all_begin(), but the callbacks may only be called
once. The separation is necessary to fix this bug.

The other reason is that we intend to go to a model where we call all
driver callbacks first, and only then start polling. This is not fully
achieved yet with this patch, as bdrv_drain_invoke() contains a
BDRV_POLL_WHILE() loop for the block driver callbacks, which can still
call callbacks for any unrelated event. It's a step in this direction
anyway.

Cc: qemu-stable@nongnu.org
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent bff55548

block/io.c

+11 −3
Original line number Diff line number Diff line
@@ -175,8 +175,10 @@ static void coroutine_fn bdrv_drain_invoke_entry(void *opaque) 
    bdrv_wakeup(bs);

}



/* Recursively call BlockDriver.bdrv_co_drain_begin/end callbacks */

static void bdrv_drain_invoke(BlockDriverState *bs, bool begin)

{

    BdrvChild *child, *tmp;

    BdrvCoDrainData data = { .bs = bs, .done = false, .begin = begin};



    if (!bs->drv || (begin && !bs->drv->bdrv_co_drain_begin) ||
@@ -187,6 +189,10 @@ static void bdrv_drain_invoke(BlockDriverState *bs, bool begin) 
    data.co = qemu_coroutine_create(bdrv_drain_invoke_entry, &data);

    bdrv_coroutine_enter(bs, data.co);

    BDRV_POLL_WHILE(bs, !data.done);



    QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) {

        bdrv_drain_invoke(child->bs, begin);

    }

}



static bool bdrv_drain_recurse(BlockDriverState *bs, bool begin)
@@ -194,9 +200,6 @@ static bool bdrv_drain_recurse(BlockDriverState *bs, bool begin) 
    BdrvChild *child, *tmp;

    bool waited;



    /* Ensure any pending metadata writes are submitted to bs->file.  */

    bdrv_drain_invoke(bs, begin);



    /* Wait for drained requests to finish */

    waited = BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0);
@@ -279,6 +282,7 @@ void bdrv_drained_begin(BlockDriverState *bs) 
        bdrv_parent_drained_begin(bs);

    }



    bdrv_drain_invoke(bs, true);

    bdrv_drain_recurse(bs, true);

}
@@ -294,6 +298,7 @@ void bdrv_drained_end(BlockDriverState *bs) 
    }



    bdrv_parent_drained_end(bs);

    bdrv_drain_invoke(bs, false);

    bdrv_drain_recurse(bs, false);

    aio_enable_external(bdrv_get_aio_context(bs));

}
@@ -372,6 +377,8 @@ void bdrv_drain_all_begin(void) 
            aio_context_acquire(aio_context);

            for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {

                if (aio_context == bdrv_get_aio_context(bs)) {

                    /* FIXME Calling this multiple times is wrong */

                    bdrv_drain_invoke(bs, true);

                    waited |= bdrv_drain_recurse(bs, true);

                }

            }
@@ -393,6 +400,7 @@ void bdrv_drain_all_end(void) 
        aio_context_acquire(aio_context);

        aio_enable_external(aio_context);

        bdrv_parent_drained_end(bs);

        bdrv_drain_invoke(bs, false);

        bdrv_drain_recurse(bs, false);

        aio_context_release(aio_context);

    }