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D21574.1794792941.diff
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Index: sys/kern/vfs_subr.c
===================================================================
--- sys/kern/vfs_subr.c
+++ sys/kern/vfs_subr.c
@@ -73,6 +73,7 @@
#include <sys/priv.h>
#include <sys/reboot.h>
#include <sys/refcount.h>
+#include <sys/rmlock.h>
#include <sys/rwlock.h>
#include <sys/sched.h>
#include <sys/sleepqueue.h>
@@ -637,10 +638,23 @@
int
vfs_busy(struct mount *mp, int flags)
{
+ struct rm_priotracker tracker;
MPASS((flags & ~MBF_MASK) == 0);
CTR3(KTR_VFS, "%s: mp %p with flags %d", __func__, mp, flags);
+ if (vfs_op_thread_enter(mp, &tracker)) {
+ MPASS((mp->mnt_kern_flag & MNTK_DRAINING) == 0);
+ MPASS((mp->mnt_kern_flag & MNTK_UNMOUNT) == 0);
+ MPASS((mp->mnt_kern_flag & MNTK_REFEXPIRE) == 0);
+ MNT_REF_FASTPATH(mp);
+ atomic_add_int(&mp->mnt_lockref, 1);
+ if (flags & MBF_MNTLSTLOCK)
+ mtx_unlock(&mountlist_mtx);
+ vfs_op_thread_exit(mp, &tracker);
+ return (0);
+ }
+
MNT_ILOCK(mp);
MNT_REF(mp);
/*
@@ -673,7 +687,7 @@
}
if (flags & MBF_MNTLSTLOCK)
mtx_unlock(&mountlist_mtx);
- mp->mnt_lockref++;
+ atomic_add_int(&mp->mnt_lockref, 1);
MNT_IUNLOCK(mp);
return (0);
}
@@ -684,13 +698,25 @@
void
vfs_unbusy(struct mount *mp)
{
+ struct rm_priotracker tracker;
+ int c;
CTR2(KTR_VFS, "%s: mp %p", __func__, mp);
+
+ if (vfs_op_thread_enter(mp, &tracker)) {
+ MPASS((mp->mnt_kern_flag & MNTK_DRAINING) == 0);
+ c = atomic_fetchadd_int(&mp->mnt_lockref, -1) - 1;
+ KASSERT(c >= 0, ("%s: negative mnt_lockref %d\n", __func__, c));
+ MNT_REL_FASTPATH(mp);
+ vfs_op_thread_exit(mp, &tracker);
+ return;
+ }
+
MNT_ILOCK(mp);
MNT_REL(mp);
- KASSERT(mp->mnt_lockref > 0, ("negative mnt_lockref"));
- mp->mnt_lockref--;
- if (mp->mnt_lockref == 0 && (mp->mnt_kern_flag & MNTK_DRAINING) != 0) {
+ c = atomic_fetchadd_int(&mp->mnt_lockref, -1) - 1;
+ KASSERT(c >= 0, ("%s: negative mnt_lockref %d\n", __func__, c));
+ if (c == 0 && (mp->mnt_kern_flag & MNTK_DRAINING) != 0) {
MPASS(mp->mnt_kern_flag & MNTK_UNMOUNT);
CTR1(KTR_VFS, "%s: waking up waiters", __func__);
mp->mnt_kern_flag &= ~MNTK_DRAINING;

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