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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: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2017-12-05 12:52:09 +01:00
parent bff5554843
commit db0289b9b2
1 changed files with 11 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
block/io.c
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@ -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);
}