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dma-helpers: rewrite completion/cancellation

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This fixes various problems with completion/cancellation:

* if the io_func fails to get an AIOCB, the callback wasn't called

* If DMA encounters a bounce buffer conflict, and the DMA operation is
canceled before the bottom half fires, bad things happen.

* memory is not unmapped after cancellation, again causing problems
when doing DMA to I/O areas

* cancellation could leak the iovec

* the callback was missed if the I/O operation failed without returning
an AIOCB

and probably more that I've missed.  The patch fixes them by sharing
the cleanup code between completion and cancellation.  The dma_bdrv_cb
now returns a boolean completed/not completed flag, and the wrapper
dma_continue takes care of tasks to do upon completion.

Most of these are basically impossible in practice, but it is better
to be tidy...

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2011-09-16 16:40:02 +02:00 committed by Kevin Wolf
parent 10dc8aef41
commit c3adb5b916
1 changed files with 31 additions and 13 deletions
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44
dma-helpers.c
View file

@ -43,6 +43,7 @@ typedef struct {
QEMUSGList *sg;
uint64_t sector_num;
bool to_dev;
bool in_cancel;
int sg_cur_index;
target_phys_addr_t sg_cur_byte;
QEMUIOVector iov;
@ -58,7 +59,7 @@ static void reschedule_dma(void *opaque)
qemu_bh_delete(dbs->bh);
dbs->bh = NULL;
dma_bdrv_cb(opaque, 0);
dma_bdrv_cb(dbs, 0);
}
static void continue_after_map_failure(void *opaque)
@ -78,6 +79,26 @@ static void dma_bdrv_unmap(DMAAIOCB *dbs)
dbs->iov.iov[i].iov_len, !dbs->to_dev,
dbs->iov.iov[i].iov_len);
}
qemu_iovec_reset(&dbs->iov);
}
static void dma_complete(DMAAIOCB *dbs, int ret)
{
dma_bdrv_unmap(dbs);
if (dbs->common.cb) {
dbs->common.cb(dbs->common.opaque, ret);
}
qemu_iovec_destroy(&dbs->iov);
if (dbs->bh) {
qemu_bh_delete(dbs->bh);
dbs->bh = NULL;
}
if (!dbs->in_cancel) {
/* Requests may complete while dma_aio_cancel is in progress. In
* this case, the AIOCB should not be released because it is still
* referenced by dma_aio_cancel. */
qemu_aio_release(dbs);
}
}
static void dma_bdrv_cb(void *opaque, int ret)
@ -89,12 +110,9 @@ static void dma_bdrv_cb(void *opaque, int ret)
dbs->acb = NULL;
dbs->sector_num += dbs->iov.size / 512;
dma_bdrv_unmap(dbs);
qemu_iovec_reset(&dbs->iov);
if (dbs->sg_cur_index == dbs->sg->nsg || ret < 0) {
dbs->common.cb(dbs->common.opaque, ret);
qemu_iovec_destroy(&dbs->iov);
qemu_aio_release(dbs);
dma_complete(dbs, ret);
return;
}
@ -120,9 +138,7 @@ static void dma_bdrv_cb(void *opaque, int ret)
dbs->acb = dbs->io_func(dbs->bs, dbs->sector_num, &dbs->iov,
dbs->iov.size / 512, dma_bdrv_cb, dbs);
if (!dbs->acb) {
dma_bdrv_unmap(dbs);
qemu_iovec_destroy(&dbs->iov);
return;
dma_complete(dbs, -EIO);
}
}
@ -131,8 +147,14 @@ static void dma_aio_cancel(BlockDriverAIOCB *acb)
DMAAIOCB *dbs = container_of(acb, DMAAIOCB, common);
if (dbs->acb) {
bdrv_aio_cancel(dbs->acb);
BlockDriverAIOCB *acb = dbs->acb;
dbs->acb = NULL;
dbs->in_cancel = true;
bdrv_aio_cancel(acb);
dbs->in_cancel = false;
}
dbs->common.cb = NULL;
dma_complete(dbs, 0);
}
static AIOPool dma_aio_pool = {
@ -158,10 +180,6 @@ BlockDriverAIOCB *dma_bdrv_io(
dbs->bh = NULL;
qemu_iovec_init(&dbs->iov, sg->nsg);
dma_bdrv_cb(dbs, 0);
if (!dbs->acb) {
qemu_aio_release(dbs);
return NULL;
}
return &dbs->common;
}