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D28695.1793514173.diff
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Index: sys/kern/vfs_default.c
===================================================================
--- sys/kern/vfs_default.c
+++ sys/kern/vfs_default.c
@@ -665,7 +665,6 @@
} */ *ap;
{
struct mount *mp;
- struct mount_pcpu *mpcpu;
struct vnode *vp;
/*
@@ -678,29 +677,7 @@
* with releasing it.
*/
vp = ap->a_vp;
- mp = vp->v_mount;
- if (mp == NULL) {
- *(ap->a_mpp) = NULL;
- return (0);
- }
- if (vfs_op_thread_enter(mp, mpcpu)) {
- if (mp == vp->v_mount) {
- vfs_mp_count_add_pcpu(mpcpu, ref, 1);
- vfs_op_thread_exit(mp, mpcpu);
- } else {
- vfs_op_thread_exit(mp, mpcpu);
- mp = NULL;
- }
- } else {
- MNT_ILOCK(mp);
- if (mp == vp->v_mount) {
- MNT_REF(mp);
- MNT_IUNLOCK(mp);
- } else {
- MNT_IUNLOCK(mp);
- mp = NULL;
- }
- }
+ mp = vfs_ref_from_vp(vp);
*(ap->a_mpp) = mp;
return (0);
}
Index: sys/kern/vfs_mount.c
===================================================================
--- sys/kern/vfs_mount.c
+++ sys/kern/vfs_mount.c
@@ -449,6 +449,44 @@
* Various utility functions
*/
+/*
+ * Get a reference on a mount point from a vnode.
+ *
+ * The vnode is allowed to be passed unlocked and race against dooming. Note in
+ * such case there are no guarantees the referenced mount point will still be
+ * associated with it after the function returns.
+ */
+struct mount *
+vfs_ref_from_vp(struct vnode *vp)
+{
+ struct mount *mp;
+ struct mount_pcpu *mpcpu;
+
+ mp = atomic_load_ptr(&vp->v_mount);
+ if (__predict_false(mp == NULL)) {
+ return (mp);
+ }
+ if (vfs_op_thread_enter(mp, mpcpu)) {
+ if (__predict_true(mp == vp->v_mount)) {
+ vfs_mp_count_add_pcpu(mpcpu, ref, 1);
+ vfs_op_thread_exit(mp, mpcpu);
+ } else {
+ vfs_op_thread_exit(mp, mpcpu);
+ mp = NULL;
+ }
+ } else {
+ MNT_ILOCK(mp);
+ if (mp == vp->v_mount) {
+ MNT_REF(mp);
+ MNT_IUNLOCK(mp);
+ } else {
+ MNT_IUNLOCK(mp);
+ mp = NULL;
+ }
+ }
+ return (mp);
+}
+
void
vfs_ref(struct mount *mp)
{
Index: sys/kern/vfs_syscalls.c
===================================================================
--- sys/kern/vfs_syscalls.c
+++ sys/kern/vfs_syscalls.c
@@ -333,15 +333,13 @@
struct nameidata nd;
int error;
- NDINIT(&nd, LOOKUP, FOLLOW | LOCKSHARED | LOCKLEAF | AUDITVNODE1,
- pathseg, path, td);
+ NDINIT(&nd, LOOKUP, FOLLOW | AUDITVNODE1, pathseg, path, td);
error = namei(&nd);
if (error != 0)
return (error);
- mp = nd.ni_vp->v_mount;
- vfs_ref(mp);
+ mp = vfs_ref_from_vp(nd.ni_vp);
NDFREE_NOTHING(&nd);
- vput(nd.ni_vp);
+ vrele(nd.ni_vp);
return (kern_do_statfs(td, mp, buf));
}
Index: sys/sys/mount.h
===================================================================
--- sys/sys/mount.h
+++ sys/sys/mount.h
@@ -997,6 +997,7 @@
void vfs_mountroot(void); /* mount our root filesystem */
void vfs_mountedfrom(struct mount *, const char *from);
void vfs_notify_upper(struct vnode *, int);
+struct mount *vfs_ref_from_vp(struct vnode *);
void vfs_ref(struct mount *);
void vfs_rel(struct mount *);
struct mount *vfs_mount_alloc(struct vnode *, struct vfsconf *, const char *,

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