[src/trunk]: src/sys/kern Protect attaching and detaching lwp_info to mount w...

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

details:   https://anonhg.NetBSD.org/src/rev/81ee67f92bb7
branches:  trunk
changeset: 821780:81ee67f92bb7
user:      hannken <hannken%NetBSD.org@localhost>
date:      Fri Feb 17 08:24:07 2017 +0000

description:
Protect attaching and detaching lwp_info to mount with a mutex.

diffstat:

 sys/kern/vfs_trans.c |  47 +++++++++++++++++++++++++++++++----------------
 1 files changed, 31 insertions(+), 16 deletions(-)

diffs (141 lines):

diff -r c1fc5daa72aa -r 81ee67f92bb7 sys/kern/vfs_trans.c
--- a/sys/kern/vfs_trans.c      Fri Feb 17 07:21:28 2017 +0000
+++ b/sys/kern/vfs_trans.c      Fri Feb 17 08:24:07 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_trans.c,v 1.34 2015/08/24 22:50:32 pooka Exp $     */
+/*     $NetBSD: vfs_trans.c,v 1.35 2017/02/17 08:24:07 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 1.34 2015/08/24 22:50:32 pooka Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_trans.c,v 1.35 2017/02/17 08:24:07 hannken Exp $");
 
 /*
  * File system transaction operations.
@@ -78,6 +78,7 @@
 static specificdata_key_t lwp_data_key;        /* Our specific data key. */
 static kmutex_t vfs_suspend_lock;      /* Serialize suspensions. */
 static kmutex_t fstrans_lock;          /* Fstrans big lock. */
+static kmutex_t fstrans_mount_lock;    /* Fstrans mount big lock. */
 static kcondvar_t fstrans_state_cv;    /* Fstrans or cow state changed. */
 static kcondvar_t fstrans_count_cv;    /* Fstrans or cow count changed. */
 static pserialize_t fstrans_psz;       /* Pserialize state. */
@@ -106,6 +107,7 @@
 
        mutex_init(&vfs_suspend_lock, MUTEX_DEFAULT, IPL_NONE);
        mutex_init(&fstrans_lock, MUTEX_DEFAULT, IPL_NONE);
+       mutex_init(&fstrans_mount_lock, MUTEX_DEFAULT, IPL_NONE);
        cv_init(&fstrans_state_cv, "fstchg");
        cv_init(&fstrans_count_cv, "fstcnt");
        fstrans_psz = pserialize_create();
@@ -140,17 +142,25 @@
 {
        struct fstrans_mount_info *fmi;
 
+       mutex_enter(&fstrans_mount_lock);
+
        fmi = mp->mnt_transinfo;
-       if (atomic_dec_uint_nv(&fmi->fmi_ref_cnt) > 0)
+       KASSERT(fmi != NULL);
+       fmi->fmi_ref_cnt -= 1;
+       if (fmi->fmi_ref_cnt > 0) {
+               mutex_exit(&fstrans_mount_lock);
                return;
+       }
 
        KASSERT(fmi->fmi_state == FSTRANS_NORMAL);
        KASSERT(LIST_FIRST(&fmi->fmi_cow_handler) == NULL);
 
-       kmem_free(fmi, sizeof(*fmi));
        mp->mnt_iflag &= ~IMNT_HAS_TRANS;
        mp->mnt_transinfo = NULL;
 
+       mutex_exit(&fstrans_mount_lock);
+
+       kmem_free(fmi, sizeof(*fmi));
        vfs_destroy(mp);
 }
 
@@ -172,8 +182,10 @@
        LIST_INIT(&newfmi->fmi_cow_handler);
        newfmi->fmi_cow_change = false;
 
+       mutex_enter(&fstrans_mount_lock);
        mp->mnt_transinfo = newfmi;
        mp->mnt_iflag |= IMNT_HAS_TRANS;
+       mutex_exit(&fstrans_mount_lock);
 
        vfs_unbusy(mp, true, NULL);
 
@@ -236,6 +248,7 @@
                mutex_enter(&fstrans_lock);
                LIST_FOREACH(fli, &fstrans_fli_head, fli_list) {
                        if (fli->fli_self == NULL) {
+                               KASSERT(fli->fli_mount == NULL);
                                KASSERT(fli->fli_trans_cnt == 0);
                                KASSERT(fli->fli_cow_cnt == 0);
                                fli->fli_self = curlwp;
@@ -260,9 +273,16 @@
        /*
         * Attach the entry to the mount.
         */
-       fmi = mp->mnt_transinfo;
-       fli->fli_mount = mp;
-       atomic_inc_uint(&fmi->fmi_ref_cnt);
+       mutex_enter(&fstrans_mount_lock);
+       if (mp == NULL || (mp->mnt_iflag & IMNT_HAS_TRANS) == 0) {
+               fli = NULL;
+       } else {
+               fmi = mp->mnt_transinfo;
+               KASSERT(fmi != NULL);
+               fli->fli_mount = mp;
+               fmi->fmi_ref_cnt += 1;
+       }
+       mutex_exit(&fstrans_mount_lock);
 
        return fli;
 }
@@ -297,11 +317,9 @@
 
        ASSERT_SLEEPABLE();
 
-       if (mp == NULL || (mp->mnt_iflag & IMNT_HAS_TRANS) == 0)
+       if (mp == NULL || (fli = fstrans_get_lwp_info(mp, true)) == NULL)
                return 0;
 
-       fli = fstrans_get_lwp_info(mp, true);
-
        if (fli->fli_trans_cnt > 0) {
                KASSERT(lock_type != FSTRANS_EXCL);
                fli->fli_trans_cnt += 1;
@@ -343,11 +361,9 @@
        struct fstrans_lwp_info *fli;
        struct fstrans_mount_info *fmi;
 
-       if (mp == NULL || (mp->mnt_iflag & IMNT_HAS_TRANS) == 0)
+       if (mp == NULL || (fli = fstrans_get_lwp_info(mp, true)) == NULL)
                return;
 
-       fli = fstrans_get_lwp_info(mp, false);
-       KASSERT(fli != NULL);
        KASSERT(fli->fli_trans_cnt > 0);
 
        if (fli->fli_trans_cnt > 1) {
@@ -380,11 +396,10 @@
 {
        struct fstrans_lwp_info *fli;
 
-       if (mp == NULL || (mp->mnt_iflag & IMNT_HAS_TRANS) == 0)
+       if (mp == NULL || (fli = fstrans_get_lwp_info(mp, false)) == NULL)
                return 0;
 
-       fli = fstrans_get_lwp_info(mp, false);
-       if (fli == NULL || fli->fli_trans_cnt == 0)
+       if (fli->fli_trans_cnt == 0)
                return 0;
 
        KASSERT(fli->fli_mount == mp);