git: 39a2dc44f8d9 - main - unionfs: allow vnode lock to be held shared during VOP_OPEN
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Date: Wed, 12 Jan 2022 02:36:56 UTC
The branch main has been updated by jah:
URL: https://cgit.FreeBSD.org/src/commit/?id=39a2dc44f8d97d7db991a772d24cc119f33cf6b3
commit 39a2dc44f8d97d7db991a772d24cc119f33cf6b3
Author: Jason A. Harmening <jah@FreeBSD.org>
AuthorDate: 2022-01-03 14:47:02 +0000
Commit: Jason A. Harmening <jah@FreeBSD.org>
CommitDate: 2022-01-12 02:44:03 +0000
unionfs: allow vnode lock to be held shared during VOP_OPEN
do_execve() will hold the vnode lock shared when it calls VOP_OPEN(),
but unionfs_open() requires the lock to be held exclusive to
correctly synchronize node status updates. This requirement is
asserted in unionfs_get_node_status().
Change unionfs_open() to temporarily upgrade the lock as is already
done in unionfs_close(). Related to this, fix various cases throughout
unionfs in which vnodes are not checked for reclamation following lock
upgrades that may have temporarily dropped the lock. Also fix another
related issue in which unionfs_lock() can incorrectly add LK_NOWAIT
during a downgrade operation, which trips a lockmgr assertion.
Reviewed by: kib (prior version), markj, pho
Reported by: pho
Differential Revision: https://reviews.freebsd.org/D33729
---
sys/fs/unionfs/union_subr.c | 5 +-
sys/fs/unionfs/union_vnops.c | 129 +++++++++++++++++++++++++++++++------------
2 files changed, 96 insertions(+), 38 deletions(-)
diff --git a/sys/fs/unionfs/union_subr.c b/sys/fs/unionfs/union_subr.c
index 9a706d79f9f7..c70e8eae5580 100644
--- a/sys/fs/unionfs/union_subr.c
+++ b/sys/fs/unionfs/union_subr.c
@@ -525,8 +525,9 @@ unionfs_noderem(struct vnode *vp)
}
/*
- * Get the unionfs node status.
- * You need exclusive lock this vnode.
+ * Get the unionfs node status object for the vnode corresponding to unp,
+ * for the process that owns td. Allocate a new status object if one
+ * does not already exist.
*/
void
unionfs_get_node_status(struct unionfs_node *unp, struct thread *td,
diff --git a/sys/fs/unionfs/union_vnops.c b/sys/fs/unionfs/union_vnops.c
index 43cf415ca755..19779112941e 100644
--- a/sys/fs/unionfs/union_vnops.c
+++ b/sys/fs/unionfs/union_vnops.c
@@ -470,30 +470,73 @@ unionfs_mknod_abort:
return (error);
}
+enum unionfs_lkupgrade {
+ UNIONFS_LKUPGRADE_SUCCESS, /* lock successfully upgraded */
+ UNIONFS_LKUPGRADE_ALREADY, /* lock already held exclusive */
+ UNIONFS_LKUPGRADE_DOOMED /* lock was upgraded, but vnode reclaimed */
+};
+
+static inline enum unionfs_lkupgrade
+unionfs_upgrade_lock(struct vnode *vp)
+{
+ ASSERT_VOP_LOCKED(vp, __func__);
+
+ if (VOP_ISLOCKED(vp) == LK_EXCLUSIVE)
+ return (UNIONFS_LKUPGRADE_ALREADY);
+
+ if (vn_lock(vp, LK_UPGRADE) != 0) {
+ vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+ if (VN_IS_DOOMED(vp))
+ return (UNIONFS_LKUPGRADE_DOOMED);
+ }
+ return (UNIONFS_LKUPGRADE_SUCCESS);
+}
+
+static inline void
+unionfs_downgrade_lock(struct vnode *vp, enum unionfs_lkupgrade status)
+{
+ if (status != UNIONFS_LKUPGRADE_ALREADY)
+ vn_lock(vp, LK_DOWNGRADE | LK_RETRY);
+}
+
static int
unionfs_open(struct vop_open_args *ap)
{
struct unionfs_node *unp;
struct unionfs_node_status *unsp;
+ struct vnode *vp;
struct vnode *uvp;
struct vnode *lvp;
struct vnode *targetvp;
struct ucred *cred;
struct thread *td;
int error;
+ enum unionfs_lkupgrade lkstatus;
UNIONFS_INTERNAL_DEBUG("unionfs_open: enter\n");
KASSERT_UNIONFS_VNODE(ap->a_vp);
error = 0;
- unp = VTOUNIONFS(ap->a_vp);
- uvp = unp->un_uppervp;
- lvp = unp->un_lowervp;
+ vp = ap->a_vp;
targetvp = NULLVP;
cred = ap->a_cred;
td = ap->a_td;
+ /*
+ * The executable loader path may call this function with vp locked
+ * shared. If the vnode is reclaimed while upgrading, we can't safely
+ * use unp or do anything else unionfs- specific.
+ */
+ lkstatus = unionfs_upgrade_lock(vp);
+ if (lkstatus == UNIONFS_LKUPGRADE_DOOMED) {
+ error = ENOENT;
+ goto unionfs_open_cleanup;
+ }
+
+ unp = VTOUNIONFS(vp);
+ uvp = unp->un_uppervp;
+ lvp = unp->un_lowervp;
unionfs_get_node_status(unp, td, &unsp);
if (unsp->uns_lower_opencnt > 0 || unsp->uns_upper_opencnt > 0) {
@@ -540,13 +583,16 @@ unionfs_open(struct vop_open_args *ap)
unsp->uns_lower_opencnt++;
unsp->uns_lower_openmode = ap->a_mode;
}
- ap->a_vp->v_object = targetvp->v_object;
+ vp->v_object = targetvp->v_object;
}
unionfs_open_abort:
if (error != 0)
unionfs_tryrem_node_status(unp, unsp);
+unionfs_open_cleanup:
+ unionfs_downgrade_lock(vp, lkstatus);
+
UNIONFS_INTERNAL_DEBUG("unionfs_open: leave (%d)\n", error);
return (error);
@@ -562,23 +608,26 @@ unionfs_close(struct vop_close_args *ap)
struct vnode *vp;
struct vnode *ovp;
int error;
- int locked;
+ enum unionfs_lkupgrade lkstatus;;
UNIONFS_INTERNAL_DEBUG("unionfs_close: enter\n");
KASSERT_UNIONFS_VNODE(ap->a_vp);
- locked = 0;
vp = ap->a_vp;
- unp = VTOUNIONFS(vp);
cred = ap->a_cred;
td = ap->a_td;
+ error = 0;
- if (VOP_ISLOCKED(vp) != LK_EXCLUSIVE) {
- if (vn_lock(vp, LK_UPGRADE) != 0)
- vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
- locked = 1;
- }
+ /*
+ * If the vnode is reclaimed while upgrading, we can't safely use unp
+ * or do anything else unionfs- specific.
+ */
+ lkstatus = unionfs_upgrade_lock(vp);
+ if (lkstatus == UNIONFS_LKUPGRADE_DOOMED)
+ goto unionfs_close_cleanup;
+
+ unp = VTOUNIONFS(vp);
unionfs_get_node_status(unp, td, &unsp);
if (unsp->uns_lower_opencnt <= 0 && unsp->uns_upper_opencnt <= 0) {
@@ -618,8 +667,8 @@ unionfs_close(struct vop_close_args *ap)
unionfs_close_abort:
unionfs_tryrem_node_status(unp, unsp);
- if (locked != 0)
- vn_lock(vp, LK_DOWNGRADE | LK_RETRY);
+unionfs_close_cleanup:
+ unionfs_downgrade_lock(vp, lkstatus);
UNIONFS_INTERNAL_DEBUG("unionfs_close: leave (%d)\n", error);
@@ -1444,6 +1493,11 @@ unionfs_rmdir(struct vop_rmdir_args *ap)
VNPASS(vrefcnt(ap->a_vp) > 0, ap->a_vp);
error = unionfs_relookup_for_delete(ap->a_dvp, cnp, td);
vn_lock(ap->a_vp, LK_EXCLUSIVE | LK_RETRY);
+ /*
+ * VOP_RMDIR is dispatched against udvp, so if uvp became
+ * doomed while the lock was dropped above the target
+ * filesystem may not be able to cope.
+ */
if (error == 0 && VN_IS_DOOMED(uvp))
error = ENOENT;
if (error == 0)
@@ -1514,9 +1568,9 @@ unionfs_readdir(struct vop_readdir_args *ap)
uint64_t *cookies_bk;
int error;
int eofflag;
- int locked;
int ncookies_bk;
int uio_offset_bk;
+ enum unionfs_lkupgrade lkstatus;
UNIONFS_INTERNAL_DEBUG("unionfs_readdir: enter\n");
@@ -1524,7 +1578,6 @@ unionfs_readdir(struct vop_readdir_args *ap)
error = 0;
eofflag = 0;
- locked = 0;
uio_offset_bk = 0;
uio = ap->a_uio;
uvp = NULLVP;
@@ -1537,18 +1590,18 @@ unionfs_readdir(struct vop_readdir_args *ap)
if (vp->v_type != VDIR)
return (ENOTDIR);
- /* check the open count. unionfs needs to open before readdir. */
- if (VOP_ISLOCKED(vp) != LK_EXCLUSIVE) {
- if (vn_lock(vp, LK_UPGRADE) != 0)
- vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
- locked = 1;
- }
- unp = VTOUNIONFS(vp);
- if (unp == NULL)
+ /*
+ * If the vnode is reclaimed while upgrading, we can't safely use unp
+ * or do anything else unionfs- specific.
+ */
+ lkstatus = unionfs_upgrade_lock(vp);
+ if (lkstatus == UNIONFS_LKUPGRADE_DOOMED)
error = EBADF;
- else {
+ if (error == 0) {
+ unp = VTOUNIONFS(vp);
uvp = unp->un_uppervp;
lvp = unp->un_lowervp;
+ /* check the open count. unionfs needs open before readdir. */
unionfs_get_node_status(unp, td, &unsp);
if ((uvp != NULLVP && unsp->uns_upper_opencnt <= 0) ||
(lvp != NULLVP && unsp->uns_lower_opencnt <= 0)) {
@@ -1556,8 +1609,7 @@ unionfs_readdir(struct vop_readdir_args *ap)
error = EBADF;
}
}
- if (locked)
- vn_lock(vp, LK_DOWNGRADE | LK_RETRY);
+ unionfs_downgrade_lock(vp, lkstatus);
if (error != 0)
goto unionfs_readdir_exit;
@@ -1906,7 +1958,8 @@ unionfs_lock(struct vop_lock1_args *ap)
if ((revlock = unionfs_get_llt_revlock(vp, flags)) == 0)
panic("unknown lock type: 0x%x", flags & LK_TYPE_MASK);
- if ((vp->v_iflag & VI_OWEINACT) != 0)
+ if ((flags & LK_TYPE_MASK) != LK_DOWNGRADE &&
+ (vp->v_iflag & VI_OWEINACT) != 0)
flags |= LK_NOWAIT;
/*
@@ -2251,10 +2304,12 @@ unionfs_openextattr(struct vop_openextattr_args *ap)
if (error == 0) {
if (vn_lock(vp, LK_UPGRADE) != 0)
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
- if (tvp == unp->un_uppervp)
- unp->un_flag |= UNIONFS_OPENEXTU;
- else
- unp->un_flag |= UNIONFS_OPENEXTL;
+ if (!VN_IS_DOOMED(vp)) {
+ if (tvp == unp->un_uppervp)
+ unp->un_flag |= UNIONFS_OPENEXTU;
+ else
+ unp->un_flag |= UNIONFS_OPENEXTL;
+ }
vn_lock(vp, LK_DOWNGRADE | LK_RETRY);
}
@@ -2288,10 +2343,12 @@ unionfs_closeextattr(struct vop_closeextattr_args *ap)
if (error == 0) {
if (vn_lock(vp, LK_UPGRADE) != 0)
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
- if (tvp == unp->un_uppervp)
- unp->un_flag &= ~UNIONFS_OPENEXTU;
- else
- unp->un_flag &= ~UNIONFS_OPENEXTL;
+ if (!VN_IS_DOOMED(vp)) {
+ if (tvp == unp->un_uppervp)
+ unp->un_flag &= ~UNIONFS_OPENEXTU;
+ else
+ unp->un_flag &= ~UNIONFS_OPENEXTL;
+ }
vn_lock(vp, LK_DOWNGRADE | LK_RETRY);
}