[src/trunk]: src/sys/kern Add reference counting to alias states to prevent t...

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

details:   https://anonhg.NetBSD.org/src/rev/b7fcd91853ab
branches:  trunk
changeset: 455831:b7fcd91853ab
user:      hannken <hannken%NetBSD.org@localhost>
date:      Mon Apr 15 13:01:08 2019 +0000

description:
Add reference counting to alias states to prevent them disappearing
while still in use.

diffstat:

 sys/kern/vfs_trans.c |  20 ++++++++++++++++----
 1 files changed, 16 insertions(+), 4 deletions(-)

diffs (83 lines):

diff -r 85375f1f7de4 -r b7fcd91853ab sys/kern/vfs_trans.c
--- a/sys/kern/vfs_trans.c      Mon Apr 15 12:59:38 2019 +0000
+++ b/sys/kern/vfs_trans.c      Mon Apr 15 13:01:08 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_trans.c,v 1.58 2019/03/07 11:09:10 hannken Exp $   */
+/*     $NetBSD: vfs_trans.c,v 1.59 2019/04/15 13:01:08 hannken Exp $   */
 
 /*-
  * Copyright (c) 2007 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_trans.c,v 1.58 2019/03/07 11:09:10 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_trans.c,v 1.59 2019/04/15 13:01:08 hannken Exp $");
 
 /*
  * File system transaction operations.
@@ -71,6 +71,7 @@
        struct fstrans_lwp_info *fli_alias;
        struct fstrans_mount_info *fli_mountinfo;
        int fli_trans_cnt;
+       int fli_alias_cnt;
        int fli_cow_cnt;
        enum fstrans_lock_type fli_lock_type;
        LIST_ENTRY(fstrans_lwp_info) fli_list;
@@ -203,6 +204,7 @@
                if (fli->fli_mount != NULL)
                        fstrans_mount_dtor(fli->fli_mountinfo);
                fli_next = fli->fli_succ;
+               fli->fli_alias_cnt = 0;
                fli->fli_mount = NULL;
                fli->fli_alias = NULL;
                fli->fli_mountinfo = NULL;
@@ -300,14 +302,21 @@
                fli = *p;
                if (fli->fli_mount != NULL &&
                    fli->fli_mountinfo->fmi_gone &&
-                   fli->fli_trans_cnt == 0 && fli->fli_cow_cnt == 0) {
+                   fli->fli_trans_cnt == 0 &&
+                   fli->fli_cow_cnt == 0 &&
+                   fli->fli_alias_cnt == 0) {
                        *p = (*p)->fli_succ;
                        fstrans_mount_dtor(fli->fli_mountinfo);
+                       if (fli->fli_alias) {
+                               KASSERT(fli->fli_alias->fli_alias_cnt > 0);
+                               fli->fli_alias->fli_alias_cnt--;
+                       }
                        fli->fli_mount = NULL;
                        fli->fli_alias = NULL;
                        fli->fli_mountinfo = NULL;
                        membar_sync();
                        fli->fli_self = NULL;
+                       p = &curlwp->l_fstrans;
                } else {
                        p = &(*p)->fli_succ;
                }
@@ -343,6 +352,7 @@
                        KASSERT(fli->fli_mount == NULL);
                        KASSERT(fli->fli_trans_cnt == 0);
                        KASSERT(fli->fli_cow_cnt == 0);
+                       KASSERT(fli->fli_alias_cnt == 0);
                        fli->fli_self = curlwp;
                        fli->fli_succ = curlwp->l_fstrans;
                        curlwp->l_fstrans = fli;
@@ -378,6 +388,7 @@
 
        if (mp) {
                fli->fli_alias = fstrans_alloc_lwp_info(mp);
+               fli->fli_alias->fli_alias_cnt++;
                fli = fli->fli_alias;
        }
 
@@ -971,7 +982,8 @@
                                break;
                        }
                }
-               printf(" %d cow %d\n", fli->fli_trans_cnt, fli->fli_cow_cnt);
+               printf(" %d cow %d alias %d\n",
+                   fli->fli_trans_cnt, fli->fli_cow_cnt, fli->fli_alias_cnt);
                prefix[0] = '\0';
        }
 }