cifs: on CONFIG_HIGHMEM machines, limit the rsize/wsize to the kmap space
We currently rely on being able to kmap all of the pages in an async read or write request. If you're on a machine that has CONFIG_HIGHMEM set then that kmap space is limited, sometimes to as low as 512 slots. With 512 slots, we can only support up to a 2M r/wsize, and that's assuming that we can get our greedy little hands on all of them. There are other users however, so it's possible we'll end up stuck with a size that large. Since we can't handle a rsize or wsize larger than that currently, cap those options at the number of kmap slots we have. We could consider capping it even lower, but we currently default to a max of 1M. Might as well allow those luddites on 32 bit arches enough rope to hang themselves. A more robust fix would be to teach the send and receive routines how to contend with an array of pages so we don't need to marshal up a kvec array at all. That's a fairly significant overhaul though, so we'll need this limit in place until that's ready. Cc: <stable@vger.kernel.org> Reported-by: NJian Li <jiali@redhat.com> Signed-off-by: NJeff Layton <jlayton@redhat.com> Signed-off-by: NSteve French <smfrench@gmail.com>
Showing
想要评论请 注册 或 登录