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Re: [Qemu-devel] [Qemu-block] [PATCH] block: use drained section in bdrv
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [Qemu-block] [PATCH] block: use drained section in bdrv_close |
Date: |
Wed, 23 Dec 2015 16:55:02 -0500 (EST) |
> On 23.12.2015 11:48, Paolo Bonzini wrote:
> > bdrv_close is used when ejecting a medium.
>
> Is it still? Other than it maybe being indirectly called through
> bdrv_delete(), it shouldn't be.
Yes, through blk_remove_bs -> bdrv_unref -> bdrv_delete.
> > Use a drained section to ensure
> > that all I/O goes to either the old medium or the bitbucket.
>
> Since the BDS will be deleted after bdrv_close() has been called, where
> else would the I/O go now?
The ioeventfd could be processed during bs->drv->bdrv_close. For
example I/O could be submitted while qcow2_close's qcow2_cache_flush
yields, and the result would probably be corrupted metadata.
Paolo
> Max
>
> > Signed-off-by: Paolo Bonzini <address@hidden>
> > ---
> > block.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/block.c b/block.c
> > index 411edbf..01655de 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -2154,9 +2154,10 @@ void bdrv_close(BlockDriverState *bs)
> > bdrv_io_limits_disable(bs);
> > }
> >
> > - bdrv_drain(bs); /* complete I/O */
> > + bdrv_drained_begin(bs); /* complete I/O */
> > bdrv_flush(bs);
> > bdrv_drain(bs); /* in case flush left pending I/O */
> > +
> > notifier_list_notify(&bs->close_notifiers, bs);
> >
> > if (bs->blk) {
> > @@ -2206,6 +2207,7 @@ void bdrv_close(BlockDriverState *bs)
> > g_free(ban);
> > }
> > QLIST_INIT(&bs->aio_notifiers);
> > + bdrv_drained_end(bs);
> > }
> >
> > void bdrv_close_all(void)
> >
>
>
>