From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56843) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WDLJq-00072K-3V for qemu-devel@nongnu.org; Tue, 11 Feb 2014 16:56:48 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WDLJk-0001Zc-3h for qemu-devel@nongnu.org; Tue, 11 Feb 2014 16:56:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:5084) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WDLJj-0001ZR-SW for qemu-devel@nongnu.org; Tue, 11 Feb 2014 16:56:36 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s1BLuXpi022757 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 11 Feb 2014 16:56:34 -0500 From: Juan Quintela Date: Tue, 11 Feb 2014 22:56:31 +0100 Message-Id: <1392155791-30709-1-git-send-email-quintela@redhat.com> Subject: [Qemu-devel] [PATCH] qemu_file: use fwrite() correctly List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org 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 --- qemu-file.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/qemu-file.c b/qemu-file.c index 9473b67..f074af1 100644 --- a/qemu-file.c +++ b/qemu-file.c @@ -100,7 +100,14 @@ 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) -- 1.8.5.3