From 34c73d82ed02209bd8933da2f1f4761bb464d1d7 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Tue, 13 Jun 2017 08:39:08 -0400 Subject: umount.nfs: assume path name is canonical. /usr/bin/umount will always pass a canonical name to umount.nfs, so it is safe to disable canonicalization. When umounting an NFS filesystem, it is generally safest to not "stat" the mountpoint at all as that can block indefinitely. umount() will not block, but lstat() etc can. By disabling canonicalization in libmount, we discourage it from ever calling 'stat' family operations, and thus reduce the chance of a hang. Note that to be fully effective, this requires changes to util-linux which have not yet been accepted. When both that change and this are in effect, automounters can use "umount -c $PATH" to safely unmount a filesystem without blocking. Signed-off-by: NeilBrown Signed-off-by: Steve Dickson --- utils/mount/mount_libmount.c | 1 + 1 file changed, 1 insertion(+) diff --git a/utils/mount/mount_libmount.c b/utils/mount/mount_libmount.c index 1f01f7f..2d40657 100644 --- a/utils/mount/mount_libmount.c +++ b/utils/mount/mount_libmount.c @@ -188,6 +188,7 @@ static int umount_main(struct libmnt_context *cxt, int argc, char **argv) }; mnt_context_init_helper(cxt, MNT_ACT_UMOUNT, 0); + mnt_context_disable_canonicalize(cxt, 1); while ((c = getopt_long (argc, argv, "fvnrlh", longopts, NULL)) != -1) { -- cgit