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From 5bd906f28072f5d071705801cc1dd2e9084057bc Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Wed, 6 Nov 2013 16:53:43 +0100
Subject: [PATCH 86/87] vmdk: Only read cid from image file when opening

RH-Author: Max Reitz <mreitz@redhat.com>
Message-id: <1383756824-6921-21-git-send-email-mreitz@redhat.com>
Patchwork-id: 55575
O-Subject: [RHEL-7.0 qemu-kvm PATCH v2 20/21] vmdk: Only read cid from image file when opening
Bugzilla: 980771
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Fam Zheng <famz@redhat.com>
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>

From: Fam Zheng <famz@redhat.com>

BZ: 980771

Previously cid of parent is parsed from image file for every IO request.
We already have L1/L2 cache and don't have assumption that parent image
can be updated behind us, so remove this to get more efficiency.

The parent CID is checked only for once after opening.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit c338b6ad609699cf352c8dd6338360b7e3895ad0)

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/vmdk.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block/vmdk.c |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/block/vmdk.c b/block/vmdk.c
index ccbb0c9..8bef9f2 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -112,6 +112,7 @@ typedef struct BDRVVmdkState {
     CoMutex lock;
     uint64_t desc_offset;
     bool cid_updated;
+    bool cid_checked;
     uint32_t parent_cid;
     int num_extents;
     /* Extent array with num_extents entries, ascend ordered by address */
@@ -197,8 +198,6 @@ static int vmdk_probe(const uint8_t *buf, int buf_size, const char *filename)
     }
 }
 
-#define CHECK_CID 1
-
 #define SECTOR_SIZE 512
 #define DESC_SIZE (20 * SECTOR_SIZE)    /* 20 sectors of 512 bytes each */
 #define BUF_SIZE 4096
@@ -301,19 +300,18 @@ static int vmdk_write_cid(BlockDriverState *bs, uint32_t cid)
 
 static int vmdk_is_cid_valid(BlockDriverState *bs)
 {
-#ifdef CHECK_CID
     BDRVVmdkState *s = bs->opaque;
     BlockDriverState *p_bs = bs->backing_hd;
     uint32_t cur_pcid;
 
-    if (p_bs) {
+    if (!s->cid_checked && p_bs) {
         cur_pcid = vmdk_read_cid(p_bs, 0);
         if (s->parent_cid != cur_pcid) {
             /* CID not valid */
             return 0;
         }
     }
-#endif
+    s->cid_checked = true;
     /* CID valid */
     return 1;
 }
-- 
1.7.1