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scsi-disk: bump SCSIRequest reference count until aio completion runs 

In some cases a request may be canceled before the completion callback
runs.  Keep a reference to the request between starting an AIO operation
and the corresponding scsi_req_cancel or scsi_*_complete.

When a request has to be retried, the request can be dropped because
scsi_dma_restart_bh only looks at requests that are enqueued.  As such,
they always have at least a reference.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2011-10-25 12:53:34 +02:00 committed by Kevin Wolf
parent e88c591d63
commit c7bae6a75b
1 changed files with 45 additions and 3 deletions
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48
hw/scsi-disk.c
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@ -102,8 +102,14 @@ static void scsi_cancel_io(SCSIRequest *req)
SCSIDiskReq *r = DO_UPCAST(SCSIDiskReq, req, req);
DPRINTF("Cancel tag=0x%x\n", req->tag);
r->status &= ~(SCSI_REQ_STATUS_RETRY | SCSI_REQ_STATUS_RETRY_TYPE_MASK);
if (r->req.aiocb) {
bdrv_aio_cancel(r->req.aiocb);
/* This reference was left in by scsi_*_data. We take ownership of
* it the moment scsi_req_cancel is called, independent of whether
* bdrv_aio_cancel completes the request or not. */
scsi_req_unref(&r->req);
}
r->req.aiocb = NULL;
}
@ -134,7 +140,7 @@ static void scsi_read_complete(void * opaque, int ret)
if (ret) {
if (scsi_handle_rw_error(r, -ret, SCSI_REQ_STATUS_RETRY_READ)) {
return;
goto done;
}
}
@ -144,6 +150,11 @@ static void scsi_read_complete(void * opaque, int ret)
r->sector += n;
r->sector_count -= n;
scsi_req_data(&r->req, r->qiov.size);
done:
if (!r->req.io_canceled) {
scsi_req_unref(&r->req);
}
}
static void scsi_flush_complete(void * opaque, int ret)
@ -158,11 +169,16 @@ static void scsi_flush_complete(void * opaque, int ret)
if (ret < 0) {
if (scsi_handle_rw_error(r, -ret, SCSI_REQ_STATUS_RETRY_FLUSH)) {
return;
goto done;
}
}
scsi_req_complete(&r->req, GOOD);
done:
if (!r->req.io_canceled) {
scsi_req_unref(&r->req);
}
}
/* Read more data from scsi device into buffer. */
@ -188,6 +204,8 @@ static void scsi_read_data(SCSIRequest *req)
/* No data transfer may already be in progress */
assert(r->req.aiocb == NULL);
/* The request is used as the AIO opaque value, so add a ref. */
scsi_req_ref(&r->req);
if (r->req.cmd.mode == SCSI_XFER_TO_DEV) {
DPRINTF("Data transfer direction invalid\n");
scsi_read_complete(r, -EINVAL);
@ -196,7 +214,9 @@ static void scsi_read_data(SCSIRequest *req)
if (s->tray_open) {
scsi_read_complete(r, -ENOMEDIUM);
return;
}
n = scsi_init_iovec(r);
bdrv_acct_start(s->qdev.conf.bs, &r->acct, n * BDRV_SECTOR_SIZE, BDRV_ACCT_READ);
r->req.aiocb = bdrv_aio_readv(s->qdev.conf.bs, r->sector, &r->qiov, n,
@ -206,6 +226,13 @@ static void scsi_read_data(SCSIRequest *req)
}
}
/*
* scsi_handle_rw_error has two return values. 0 means that the error
* must be ignored, 1 means that the error has been processed and the
* caller should not do anything else for this request. Note that
* scsi_handle_rw_error always manages its reference counts, independent
* of the return value.
*/
static int scsi_handle_rw_error(SCSIDiskReq *r, int error, int type)
{
int is_read = (type == SCSI_REQ_STATUS_RETRY_READ);
@ -226,6 +253,11 @@ static int scsi_handle_rw_error(SCSIDiskReq *r, int error, int type)
bdrv_mon_event(s->qdev.conf.bs, BDRV_ACTION_STOP, is_read);
vm_stop(RUN_STATE_IO_ERROR);
bdrv_iostatus_set_err(s->qdev.conf.bs, error);
/* No need to save a reference, because scsi_dma_restart_bh just
* looks at the request list. If a request is canceled, the
* retry request is just dropped.
*/
} else {
switch (error) {
case ENOMEDIUM:
@ -259,7 +291,7 @@ static void scsi_write_complete(void * opaque, int ret)
if (ret) {
if (scsi_handle_rw_error(r, -ret, SCSI_REQ_STATUS_RETRY_WRITE)) {
return;
goto done;
}
}
@ -273,6 +305,11 @@ static void scsi_write_complete(void * opaque, int ret)
DPRINTF("Write complete tag=0x%x more=%d\n", r->req.tag, r->qiov.size);
scsi_req_data(&r->req, r->qiov.size);
}
done:
if (!r->req.io_canceled) {
scsi_req_unref(&r->req);
}
}
static void scsi_write_data(SCSIRequest *req)
@ -284,6 +321,8 @@ static void scsi_write_data(SCSIRequest *req)
/* No data transfer may already be in progress */
assert(r->req.aiocb == NULL);
/* The request is used as the AIO opaque value, so add a ref. */
scsi_req_ref(&r->req);
if (r->req.cmd.mode != SCSI_XFER_TO_DEV) {
DPRINTF("Data transfer direction invalid\n");
scsi_write_complete(r, -EINVAL);
@ -294,6 +333,7 @@ static void scsi_write_data(SCSIRequest *req)
if (n) {
if (s->tray_open) {
scsi_write_complete(r, -ENOMEDIUM);
return;
}
bdrv_acct_start(s->qdev.conf.bs, &r->acct, n * BDRV_SECTOR_SIZE, BDRV_ACCT_WRITE);
r->req.aiocb = bdrv_aio_writev(s->qdev.conf.bs, r->sector, &r->qiov, n,
@ -1332,6 +1372,8 @@ static int32_t scsi_send_command(SCSIRequest *req, uint8_t *buf)
r->iov.iov_len = rc;
break;
case SYNCHRONIZE_CACHE:
/* The request is used as the AIO opaque value, so add a ref. */
scsi_req_ref(&r->req);
bdrv_acct_start(s->qdev.conf.bs, &r->acct, 0, BDRV_ACCT_FLUSH);
r->req.aiocb = bdrv_aio_flush(s->qdev.conf.bs, scsi_flush_complete, r);
if (r->req.aiocb == NULL) {