From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41571) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XorSo-00041Y-EZ for qemu-devel@nongnu.org; Thu, 13 Nov 2014 05:17:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XorSg-0004JG-NH for qemu-devel@nongnu.org; Thu, 13 Nov 2014 05:17:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47235) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XorSg-0004Iw-G1 for qemu-devel@nongnu.org; Thu, 13 Nov 2014 05:17:10 -0500 From: Markus Armbruster Date: Thu, 13 Nov 2014 11:17:02 +0100 Message-Id: <1415873823-13844-4-git-send-email-armbru@redhat.com> In-Reply-To: <1415873823-13844-1-git-send-email-armbru@redhat.com> References: <1415873823-13844-1-git-send-email-armbru@redhat.com> Subject: [Qemu-devel] [PATCH v2 3/4] raw-posix: Fix try_seek_hole()'s handling of SEEK_DATA failure List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, famz@redhat.com, tony@bakeyournoodle.com, mreitz@redhat.com, stefanha@redhat.com, pbonzini@redhat.com When SEEK_HOLE tells us we're in a hole, we try SEEK_DATA to find its end. When that fails, we pretend the hole extends to the end of file. Wrong. Except when SEEK_END fails, we screw up and claim it extends to offset -1. More wrong. Fortunately, these seeks are very unlikely to fail. Fix it anyway, by returning failure. The caller will then pretend there are no holes. Inaccurate, but safe. Signed-off-by: Markus Armbruster --- block/raw-posix.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/block/raw-posix.c b/block/raw-posix.c index fd80d84..2a12a50 100644 --- a/block/raw-posix.c +++ b/block/raw-posix.c @@ -1494,8 +1494,9 @@ static int try_seek_hole(BlockDriverState *bs, off_t start, off_t *data, } else { /* On a hole. We need another syscall to find its end. */ *data = lseek(s->fd, start, SEEK_DATA); - if (*data == -1) { - *data = lseek(s->fd, 0, SEEK_END); + if (*data < 0) { + /* no idea where the hole ends, give up (unlikely to happen) */ + return -errno; } } -- 1.9.3