Commit 1f3ddfcb authored by Stefan Hajnoczi's avatar Stefan Hajnoczi
Browse files

Revert "qed: Implement .bdrv_drain" 



This reverts commit df9a681d.

Note that commit df9a681d included some
unrelated hunks, possibly due to a merge failure or an overlooked
squash.  This only reverts the qed .bdrv_drain() implementation.

The qed .bdrv_drain() implementation is unsafe and can lead to a double
request completion.

Paolo Bonzini reports:
"The problem is that bdrv_qed_drain calls qed_plug_allocating_write_reqs
unconditionally, but this is not correct if an allocating write is
queued.  In this case, qed_unplug_allocating_write_reqs will restart the
allocating write and possibly cause it to complete.  The aiocb however
is still in use for the L2/L1 table writes, and will then be completed
again as soon as the table writes are stable."

For QEMU 2.6 we can simply revert this commit.  A full solution for the
qed need check timer may be added if the bdrv_drain() implementation is
extended.

Reported-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-id: 1457431876-8475-1-git-send-email-stefanha@redhat.com
parent 147dfab7

block/qed.c

+0 −13
Original line number Diff line number Diff line
@@ -377,18 +377,6 @@ static void bdrv_qed_attach_aio_context(BlockDriverState *bs, 
    }

}



static void bdrv_qed_drain(BlockDriverState *bs)

{

    BDRVQEDState *s = bs->opaque;



    /* Cancel timer and start doing I/O that were meant to happen as if it

     * fired, that way we get bdrv_drain() taking care of the ongoing requests

     * correctly. */

    qed_cancel_need_check_timer(s);

    qed_plug_allocating_write_reqs(s);

    bdrv_aio_flush(s->bs, qed_clear_need_check, s);

}



static int bdrv_qed_open(BlockDriverState *bs, QDict *options, int flags,

                         Error **errp)

{
@@ -1694,7 +1682,6 @@ static BlockDriver bdrv_qed = { 
    .bdrv_check               = bdrv_qed_check,

    .bdrv_detach_aio_context  = bdrv_qed_detach_aio_context,

    .bdrv_attach_aio_context  = bdrv_qed_attach_aio_context,

    .bdrv_drain               = bdrv_qed_drain,

};



static void bdrv_qed_init(void)