From 630c26893d6dc7713c0fcfc3c09d6bfe536a6ce3 Mon Sep 17 00:00:00 2001 From: Sripathi Kodi Date: Fri, 20 Aug 2010 16:17:47 +0530 Subject: [PATCH] virtio-9p: Change handling of flags in open() path for 9P2000.L This patch applies on top of 9P2000.L patches that we have on the list. I took a look at how 9P server is handling open() flags in 9P2000.L path. I think we can do away with the valid_flags() function and simplify the code. The reasoning is as follows: O_NOCTTY: (If the file is a terminal, don't make it the controlling terminal of the process even though the process does not have a controlling terminal) By the time the control reaches 9P client it is clear that what we have is not a terminal device. Hence it does not matter what we do with this flag. In any case 9P server can filter this flag out before making the syscall. O_NONBLOCK: (Don't block if i) Can't read/write to the file ii) Can't get locks) This has an impact on FIFOs, but also on file locks. Hence we can pass it down to the system call. O_ASYNC: From the manpage: O_ASYNC Enable signal-driven I/O: generate a signal (SIGIO by default, but this can be changed via fcntl(2)) when input or output becomes pos- sible on this file descriptor. This feature is only available for terminals, pseudo-terminals, sockets, and (since Linux 2.6) pipes and FIFOs. See fcntl(2) for further details. Again, this does not make any impact on regular files handled by 9P. Also, we don't want 9P server to receive SIGIO. Hence I think 9P server can filter this flag out before making the syscall. O_CLOEXEC: This flag makes sense only on the client. If guest user space sets this flag the guest VFS will take care of calling close() on the fd if an exec() happens. Hence 9P client need not be bothered with this flag. Also I think QEMU will not do an exec, but if it does, it makes sense to close these fds. Hence we can pass this flag down to the syscall. O_CREAT: Since we are in open() path it means we have confirmed that the file exists. Hence there is no need to pass O_CREAT flag down to the system. In fact on some versions of glibc this causes problems, because we pass O_CREAT flag, but don't have permission bits. Hence we can just mask this flag out. So in summary: Mask out: O_NOCTTY O_ASYNC O_CREAT Pass-through: O_NONBLOCK O_CLOEXEC Signed-off-by: Sripathi Kodi Signed-off-by: Venkateswararao Jujjuri --- hw/virtio-9p.c | 14 +------------- 1 file changed, 1 insertion(+), 13 deletions(-) diff --git a/hw/virtio-9p.c b/hw/virtio-9p.c index 4b15ce7197..32fa3bcc5c 100644 --- a/hw/virtio-9p.c +++ b/hw/virtio-9p.c @@ -1684,15 +1684,6 @@ out: qemu_free(vs); } -static inline int valid_flags(int flag) -{ - if (flag & O_NOCTTY || flag & O_NONBLOCK || flag & O_ASYNC || - flag & O_CLOEXEC) - return 0; - else - return 1; -} - static void v9fs_open_post_lstat(V9fsState *s, V9fsOpenState *vs, int err) { int flags; @@ -1709,11 +1700,8 @@ static void v9fs_open_post_lstat(V9fsState *s, V9fsOpenState *vs, int err) v9fs_open_post_opendir(s, vs, err); } else { if (s->proto_version == V9FS_PROTO_2000L) { - if (!valid_flags(vs->mode)) { - err = -EINVAL; - goto out; - } flags = vs->mode; + flags &= ~(O_NOCTTY | O_ASYNC | O_CREAT); } else { flags = omode_to_uflags(vs->mode); } -- GitLab