From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60148) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WFnzI-00012N-OJ for qemu-devel@nongnu.org; Tue, 18 Feb 2014 11:57:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WFnzC-0000ug-JP for qemu-devel@nongnu.org; Tue, 18 Feb 2014 11:57:40 -0500 Received: from mx1.redhat.com ([209.132.183.28]:3305) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WFnzC-0000uW-BR for qemu-devel@nongnu.org; Tue, 18 Feb 2014 11:57:34 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s1IGe1WC016691 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 18 Feb 2014 11:40:02 -0500 From: Markus Armbruster References: <1392163249-6983-1-git-send-email-quintela@redhat.com> Date: Tue, 18 Feb 2014 17:39:58 +0100 In-Reply-To: <1392163249-6983-1-git-send-email-quintela@redhat.com> (Juan Quintela's message of "Wed, 12 Feb 2014 01:00:49 +0100") Message-ID: <87ob24qsrl.fsf@blackfin.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v2] qemu_file: use fwrite() correctly List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Juan Quintela Cc: qemu-devel@nongnu.org Juan Quintela writes: > 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, the 1st > time it returns 0, after that it returns 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). On the 1st fwrite() for the read-only filesystem, > it returns an errno of -EPIPE, that is exactly what has failed. > > 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 Reviewed-by: Markus Armbruster