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From 91a73a0f154a7d8f2c4949ea882f684d55c916e4 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 18 Oct 2013 08:14:47 +0200
Subject: [PATCH 22/81] block: look for zero blocks in bs->file

RH-Author: Paolo Bonzini <pbonzini@redhat.com>
Message-id: <1382084091-16636-23-git-send-email-pbonzini@redhat.com>
Patchwork-id: 55005
O-Subject: [RHEL 7.0 qemu-kvm PATCH 22/26] block: look for zero blocks in bs->file
Bugzilla: 989646
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 5daa74a6ebce7543aaad178c4061dc087bb4c705)
---
 block.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/block.c b/block.c
index 2a4a9dd..f993b2e 100644
--- a/block.c
+++ b/block.c
@@ -3041,7 +3041,7 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
 {
     int64_t length;
     int64_t n;
-    int64_t ret;
+    int64_t ret, ret2;
 
     length = bdrv_getlength(bs);
     if (length < 0) {
@@ -3083,6 +3083,20 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
             }
         }
     }
+
+    if (bs->file &&
+        (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
+        (ret & BDRV_BLOCK_OFFSET_VALID)) {
+        ret2 = bdrv_co_get_block_status(bs->file, ret >> BDRV_SECTOR_BITS,
+                                        *pnum, pnum);
+        if (ret2 >= 0) {
+            /* Ignore errors.  This is just providing extra information, it
+             * is useful but not necessary.
+             */
+            ret |= (ret2 & BDRV_BLOCK_ZERO);
+        }
+    }
+
     return ret;
 }
 
-- 
1.7.1