Author: markj
Date: Wed Oct 25 01:07:12 2017
New Revision: 324966
URL: https://svnweb.freebsd.org/changeset/base/324966
Log:
MFC r324704:
Fix a racy VI_DOOMED check in MNT_VNODE_FOREACH_ALL().
Modified:
stable/10/sys/kern/vfs_subr.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/kern/vfs_subr.c
==============================================================================
--- stable/10/sys/kern/vfs_subr.c Wed Oct 25 00:51:00 2017
(r324965)
+++ stable/10/sys/kern/vfs_subr.c Wed Oct 25 01:07:12 2017
(r324966)
@@ -4868,12 +4868,18 @@ __mnt_vnode_next_all(struct vnode **mvp, struct mount
kern_yield(PRI_USER);
MNT_ILOCK(mp);
KASSERT((*mvp)->v_mount == mp, ("marker vnode mount list mismatch"));
- vp = TAILQ_NEXT(*mvp, v_nmntvnodes);
- while (vp != NULL && (vp->v_type == VMARKER ||
- (vp->v_iflag & VI_DOOMED) != 0))
- vp = TAILQ_NEXT(vp, v_nmntvnodes);
-
- /* Check if we are done */
+ for (vp = TAILQ_NEXT(*mvp, v_nmntvnodes); vp != NULL;
+ vp = TAILQ_NEXT(vp, v_nmntvnodes)) {
+ /* Allow a racy peek at VI_DOOMED to save a lock acquisition. */
+ if (vp->v_type == VMARKER || (vp->v_iflag & VI_DOOMED) != 0)
+ continue;
+ VI_LOCK(vp);
+ if ((vp->v_iflag & VI_DOOMED) != 0) {
+ VI_UNLOCK(vp);
+ continue;
+ }
+ break;
+ }
if (vp == NULL) {
__mnt_vnode_markerfree_all(mvp, mp);
/* MNT_IUNLOCK(mp); -- done in above function */
@@ -4882,7 +4888,6 @@ __mnt_vnode_next_all(struct vnode **mvp, struct mount
}
TAILQ_REMOVE(&mp->mnt_nvnodelist, *mvp, v_nmntvnodes);
TAILQ_INSERT_AFTER(&mp->mnt_nvnodelist, vp, *mvp, v_nmntvnodes);
- VI_LOCK(vp);
MNT_IUNLOCK(mp);
return (vp);
}
@@ -4895,14 +4900,20 @@ __mnt_vnode_first_all(struct vnode **mvp, struct mount
*mvp = malloc(sizeof(struct vnode), M_VNODE_MARKER, M_WAITOK | M_ZERO);
MNT_ILOCK(mp);
MNT_REF(mp);
+ (*mvp)->v_mount = mp;
(*mvp)->v_type = VMARKER;
- vp = TAILQ_FIRST(&mp->mnt_nvnodelist);
- while (vp != NULL && (vp->v_type == VMARKER ||
- (vp->v_iflag & VI_DOOMED) != 0))
- vp = TAILQ_NEXT(vp, v_nmntvnodes);
-
- /* Check if we are done */
+ TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes) {
+ /* Allow a racy peek at VI_DOOMED to save a lock acquisition. */
+ if (vp->v_type == VMARKER || (vp->v_iflag & VI_DOOMED) != 0)
+ continue;
+ VI_LOCK(vp);
+ if ((vp->v_iflag & VI_DOOMED) != 0) {
+ VI_UNLOCK(vp);
+ continue;
+ }
+ break;
+ }
if (vp == NULL) {
MNT_REL(mp);
MNT_IUNLOCK(mp);
@@ -4910,13 +4921,10 @@ __mnt_vnode_first_all(struct vnode **mvp, struct mount
*mvp = NULL;
return (NULL);
}
- (*mvp)->v_mount = mp;
TAILQ_INSERT_AFTER(&mp->mnt_nvnodelist, vp, *mvp, v_nmntvnodes);
- VI_LOCK(vp);
MNT_IUNLOCK(mp);
return (vp);
}
-
void
__mnt_vnode_markerfree_all(struct vnode **mvp, struct mount *mp)
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