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Revert "qed: Implement .bdrv_drain"

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This reverts commit df9a681dc9.

Note that commit df9a681dc9 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: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1457431876-8475-1-git-send-email-stefanha@redhat.com
This commit is contained in:
Stefan Hajnoczi 2016-03-08 10:11:16 +00:00
parent 147dfab747
commit 1f3ddfcb25
1 changed files with 0 additions and 13 deletions
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13
block/qed.c
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@ -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)