[src/trunk]: src/sys/fs/tmpfs Two fixes from rmind

[skrll <skrll%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/2f58c4701534
branches:  trunk
changeset: 347360:2f58c4701534
user:      skrll <skrll%NetBSD.org@localhost>
date:      Mon Aug 22 23:07:36 2016 +0000

description:
Two fixes from rmind

- tmpfs_node_get: restore (decrement) the node count on the error path.
- tmpfs_bytes_max: save the value of uvmexp.freetarg (since it is
  unlocked/racy).

diffstat:

 sys/fs/tmpfs/tmpfs_mem.c |  10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

diffs (42 lines):

diff -r ef03e6f01eab -r 2f58c4701534 sys/fs/tmpfs/tmpfs_mem.c
--- a/sys/fs/tmpfs/tmpfs_mem.c  Mon Aug 22 22:53:02 2016 +0000
+++ b/sys/fs/tmpfs/tmpfs_mem.c  Mon Aug 22 23:07:36 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tmpfs_mem.c,v 1.8 2014/06/13 11:57:48 pooka Exp $      */
+/*     $NetBSD: tmpfs_mem.c,v 1.9 2016/08/22 23:07:36 skrll Exp $      */
 
 /*
  * Copyright (c) 2010, 2011 The NetBSD Foundation, Inc.
@@ -35,7 +35,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tmpfs_mem.c,v 1.8 2014/06/13 11:57:48 pooka Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tmpfs_mem.c,v 1.9 2016/08/22 23:07:36 skrll Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -116,12 +116,13 @@
 tmpfs_bytes_max(struct tmpfs_mount *mp)
 {
        psize_t freepages = tmpfs_mem_info(false);
+       int freetarg = uvmexp.freetarg; // XXX unlocked
        uint64_t avail_mem;
 
-       if (freepages < uvmexp.freetarg) {
+       if (freepages < freetarg) {
                freepages = 0;
        } else {
-               freepages -= uvmexp.freetarg;
+               freepages -= freetarg;
        }
        avail_mem = round_page(mp->tm_bytes_used) + (freepages << PAGE_SHIFT);
        return MIN(mp->tm_mem_limit, avail_mem);
@@ -187,6 +188,7 @@
                return NULL;
        }
        if (!tmpfs_mem_incr(mp, sizeof(struct tmpfs_node))) {
+               atomic_dec_uint(&mp->tm_nodes_cnt);
                return NULL;
        }
        return pool_get(&tmpfs_node_pool, PR_WAITOK);