tst-zfs-mount.so: Disable reference count check

Commit 951cca4 ("Revert "vfs/zfs: Sync vnode and znode refcounts")
forgot to disable ZFS reference count test case.

Reported-by: Avi Kivity <avi@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
zfs: Set f_fsid in zfs_statfs

Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
vfs/zfs: Add st_dev field support to stat

Tomek says:

Some programs rely on the fact that the (stat.st_ino, stat.st_dev) pair
uniquely identifies the file.
In OSv only st_ino is set by vn_stat(), st_dev is zeroed. It is possible that
files on different file systems will have the same inode number and hence
appear as referring to the same file.

Spotted during code inspection of openssl and vfs, I didn't run into any issue
related to that yet.

This patch addresses the issue #216

Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
tests: Check st_dev and f_fsid validity

Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Fix uma_zone cache regression

In commit 08835b4e608eddcbd0ce17e3ef7a813d7b239731, we turned off uma
allocation caching when CONF_debug_memory is on because it hid bugs.
Or at least, this is what was *intended*. What the patch actually did
was the opposite - it turned off the cache in the normal compilation!

This caused a deterioration of UDP memcached performance, from 159,000
to 131,000 req/sec. This was the second half of the recent memcached
performance deterioration (see issue #227).

Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>