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From 2f66e62873ef54bd27ec6e063c8b4f3f11e2413d Mon Sep 17 00:00:00 2001
From: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
Date: Mon, 10 Mar 2014 17:41:43 +0100
Subject: [PATCH 15/16] qemu_file: use fwrite() correctly

RH-Author: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
Message-id: <1394473304-7190-2-git-send-email-dgilbert@redhat.com>
Patchwork-id: 58073
O-Subject: [RHEL-7.0 qemu-kvm PATCH v2 1/2] qemu_file: use fwrite() correctly
Bugzilla: 1005103
RH-Acked-by: Juan Quintela <quintela@redhat.com>
RH-Acked-by: Eric Blake <eblake@redhat.com>
RH-Acked-by: Amit Shah <amit.shah@redhat.com>

From: Juan Quintela <quintela@redhat.com>

fwrite() returns the number of items written.  But when there is one
error, it can return a short write.

In the particular bug that I was tracking, I did a migration to a
read-only filesystem.  And it was able to finish the migration
correctly.  fwrite() never returned a negative error code, nor zero,
always 4096. (migration writes chunks of about 14000 bytes).  And it
was able to "complete" the migration with success (yes, reading the
file was a bit more difficult).

To add insult to injury, if your amount of memory was big enough (12GB
on my case), it overwrote some important structure, and from them,
malloc failed.  This check makes the problem go away.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
(cherry picked from commit aded6539d983280212e08d09f14157b1cb4d58cc)

Conflicts:
	qemu-file.c

Code still in savevm.c
---
 savevm.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 savevm.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/savevm.c b/savevm.c
index bd37959..94121a2 100644
--- a/savevm.c
+++ b/savevm.c
@@ -211,7 +211,14 @@ static int stdio_get_fd(void *opaque)
 static int stdio_put_buffer(void *opaque, const uint8_t *buf, int64_t pos, int size)
 {
     QEMUFileStdio *s = opaque;
-    return fwrite(buf, 1, size, s->stdio_file);
+    int res;
+
+    res = fwrite(buf, 1, size, s->stdio_file);
+
+    if (res != size) {
+        return -EIO;	/* fake errno value */
+    }
+    return res;
 }
 
 static int stdio_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
-- 
1.7.1