From 8406a85d6b78d2f3478a204b5eab0cd714fe9aa4 Mon Sep 17 00:00:00 2001
From: Markus Armbruster <armbru@redhat.com>
Date: Fri, 31 Oct 2014 16:29:53 +0100
Subject: [PATCH 16/19] virtio-blk: Bypass error action and I/O accounting on
 invalid r/w

Message-id: <1414772996-17272-3-git-send-email-armbru@redhat.com>
Patchwork-id: 62014
O-Subject: [PATCH RHEL-7.1 qemu-kvm 2/5] virtio-blk: Bypass error action and I/O accounting on invalid r/w
Bugzilla: 1085232
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Fam Zheng <famz@redhat.com>

When a device model's I/O operation fails, we execute the error
action.  This lets layers above QEMU implement thin provisioning, or
attempt to correct errors before they reach the guest.  But when the
I/O operation fails because it's invalid, reporting the error to the
guest is the only sensible action.

If the guest's read or write asks for an invalid sector range, fail
the request right away, without considering the error action.  No
change with error action BDRV_ACTION_REPORT.

Furthermore, bypass I/O accounting, because we want to track only I/O
that actually reaches the block layer.

The next commit will extend "invalid sector range" to cover attempts
to read/write beyond the end of the medium.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 42e38c1fd0199155d32f3464aedce282d3d7f6a1)

Straightforward semantic conflict: requests still have to be freed
with g_free() because we don't have commit 671ec3f.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/block/virtio-blk.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 0f1d3ec..ffb311c 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -300,15 +300,16 @@ static void virtio_blk_handle_write(VirtIOBlockReq *req, MultiReqBuffer *mrb)
 
     sector = ldq_p(&req->out->sector);
 
-    bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_WRITE);
-
     trace_virtio_blk_handle_write(req, sector, req->qiov.size / 512);
 
     if (!virtio_blk_sect_range_ok(req->dev, sector, req->qiov.size)) {
-        virtio_blk_rw_complete(req, -EIO);
+        virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
+        g_free(req);
         return;
     }
 
+    bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_WRITE);
+
     if (mrb->num_writes == 32) {
         virtio_submit_multiwrite(req->dev->bs, mrb);
     }
@@ -330,14 +331,15 @@ static void virtio_blk_handle_read(VirtIOBlockReq *req)
 
     sector = ldq_p(&req->out->sector);
 
-    bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_READ);
-
     trace_virtio_blk_handle_read(req, sector, req->qiov.size / 512);
 
     if (!virtio_blk_sect_range_ok(req->dev, sector, req->qiov.size)) {
-        virtio_blk_rw_complete(req, -EIO);
+        virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
+        g_free(req);
         return;
     }
+
+    bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_READ);
     bdrv_aio_readv(req->dev->bs, sector, &req->qiov,
                    req->qiov.size / BDRV_SECTOR_SIZE,
                    virtio_blk_rw_complete, req);
-- 
1.8.3.1