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From 69fe324e32aad7e1afc6ad14021a6a08ad52646c Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Sat, 13 Jun 2015 16:22:27 +0200
Subject: [PATCH 33/42] block: Respect underlying file's EOF

Message-id: <1434212556-3927-34-git-send-email-mreitz@redhat.com>
Patchwork-id: 66052
O-Subject: [RHEL-7.2 qemu-kvm PATCH 33/42] block: Respect underlying file's EOF
Bugzilla: 1129893
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
RH-Acked-by: Fam Zheng <famz@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

BZ: 1129893

When falling through to the underlying file in
bdrv_co_get_block_status(), if it returns that the query offset is
beyond the file end (by setting *pnum to 0), return the range to be
zero and do not let the number of sectors for which information could be
obtained be overwritten.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 59c9a95fd29cfb3296ee58e8a446df251d14a459)

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/block.c b/block.c
index 22ab762..fa6e192 100644
--- a/block.c
+++ b/block.c
@@ -3797,13 +3797,24 @@ 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)) {
+        int file_pnum;
+
         ret2 = bdrv_co_get_block_status(bs->file, ret >> BDRV_SECTOR_BITS,
-                                        *pnum, pnum);
+                                        *pnum, &file_pnum);
         if (ret2 >= 0) {
             /* Ignore errors.  This is just providing extra information, it
              * is useful but not necessary.
              */
-            ret |= (ret2 & BDRV_BLOCK_ZERO);
+            if (!file_pnum) {
+                /* !file_pnum indicates an offset at or beyond the EOF; it is
+                 * perfectly valid for the format block driver to point to such
+                 * offsets, so catch it and mark everything as zero */
+                ret |= BDRV_BLOCK_ZERO;
+            } else {
+                /* Limit request to the range reported by the protocol driver */
+                *pnum = file_pnum;
+                ret |= (ret2 & BDRV_BLOCK_ZERO);
+            }
         }
     }
 
-- 
1.8.3.1