git: bb24eaea4982 - main - vn_lock_pair(): allow to request shared locking
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Date: Fri, 07 Apr 2023 22:59:39 UTC
The branch main has been updated by kib:
URL: https://cgit.FreeBSD.org/src/commit/?id=bb24eaea498268572aa140c35c02e02884cdf930
commit bb24eaea498268572aa140c35c02e02884cdf930
Author: Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2023-04-06 04:11:08 +0000
Commit: Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2023-04-07 22:58:26 +0000
vn_lock_pair(): allow to request shared locking
If either of vnodes is shared locked, lock must not be recursed.
Requested by: rmacklem
Reviewed by: markj, rmacklem
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D39444
---
sys/fs/unionfs/union_subr.c | 3 +-
sys/kern/vfs_mount.c | 2 +-
sys/kern/vfs_vnops.c | 86 +++++++++++++++++++++++++++++++--------------
sys/sys/vnode.h | 4 +--
sys/ufs/ffs/ffs_softdep.c | 10 +++---
sys/ufs/ufs/ufs_vnops.c | 2 +-
6 files changed, 71 insertions(+), 36 deletions(-)
diff --git a/sys/fs/unionfs/union_subr.c b/sys/fs/unionfs/union_subr.c
index 42437f1e3840..264d37634949 100644
--- a/sys/fs/unionfs/union_subr.c
+++ b/sys/fs/unionfs/union_subr.c
@@ -388,7 +388,8 @@ unionfs_nodeget(struct mount *mp, struct vnode *uppervp,
KASSERT(dvp != NULL || (vp->v_vflag & VV_ROOT) != 0,
("%s: NULL dvp for non-root vp %p", __func__, vp));
- vn_lock_pair(lowervp, false, uppervp, false);
+ vn_lock_pair(lowervp, false, LK_EXCLUSIVE, uppervp, false,
+ LK_EXCLUSIVE);
error = insmntque1(vp, mp);
if (error != 0) {
unionfs_nodeget_cleanup(vp, unp);
diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index 6233d4c3741a..bf532df335bf 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -1273,7 +1273,7 @@ vfs_domount_first(
* Use vn_lock_pair to avoid establishing an ordering between vnodes
* from different filesystems.
*/
- vn_lock_pair(vp, false, newdp, false);
+ vn_lock_pair(vp, false, LK_EXCLUSIVE, newdp, false, LK_EXCLUSIVE);
VI_LOCK(vp);
vp->v_iflag &= ~VI_MOUNT;
diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index 1d90f76f9cd6..05cc0cfda16e 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -3753,50 +3753,74 @@ vn_lock_pair_pause(const char *wmesg)
/*
* Lock pair of vnodes vp1, vp2, avoiding lock order reversal.
- * vp1_locked indicates whether vp1 is exclusively locked; if not, vp1
- * must be unlocked. Same for vp2 and vp2_locked. One of the vnodes
- * can be NULL.
+ * vp1_locked indicates whether vp1 is locked; if not, vp1 must be
+ * unlocked. Same for vp2 and vp2_locked. One of the vnodes can be
+ * NULL.
*
- * The function returns with both vnodes exclusively locked, and
- * guarantees that it does not create lock order reversal with other
- * threads during its execution. Both vnodes could be unlocked
- * temporary (and reclaimed).
+ * The function returns with both vnodes exclusively or shared locked,
+ * according to corresponding lkflags, and guarantees that it does not
+ * create lock order reversal with other threads during its execution.
+ * Both vnodes could be unlocked temporary (and reclaimed).
+ *
+ * If requesting shared locking, locked vnode lock must not be recursed.
*/
void
-vn_lock_pair(struct vnode *vp1, bool vp1_locked, struct vnode *vp2,
- bool vp2_locked)
+vn_lock_pair(struct vnode *vp1, bool vp1_locked, int lkflags1,
+ struct vnode *vp2, bool vp2_locked, int lkflags2)
{
int error;
+ MPASS(lkflags1 == LK_SHARED || lkflags1 == LK_EXCLUSIVE);
+ MPASS(lkflags2 == LK_SHARED || lkflags2 == LK_EXCLUSIVE);
+
if (vp1 == NULL && vp2 == NULL)
return;
+
if (vp1 != NULL) {
- if (vp1_locked)
- ASSERT_VOP_ELOCKED(vp1, "vp1");
- else
+ if (lkflags1 == LK_SHARED &&
+ (vp1->v_vnlock->lock_object.lo_flags & LK_NOSHARE) != 0)
+ lkflags1 = LK_EXCLUSIVE;
+ if (vp1_locked && VOP_ISLOCKED(vp1) != LK_EXCLUSIVE) {
+ ASSERT_VOP_LOCKED(vp1, "vp1");
+ if (lkflags1 == LK_EXCLUSIVE) {
+ VOP_UNLOCK(vp1);
+ ASSERT_VOP_UNLOCKED(vp1,
+ "vp1 shared recursed");
+ vp1_locked = false;
+ }
+ } else if (!vp1_locked)
ASSERT_VOP_UNLOCKED(vp1, "vp1");
} else {
vp1_locked = true;
}
+
if (vp2 != NULL) {
- if (vp2_locked)
- ASSERT_VOP_ELOCKED(vp2, "vp2");
- else
+ if (lkflags2 == LK_SHARED &&
+ (vp2->v_vnlock->lock_object.lo_flags & LK_NOSHARE) != 0)
+ lkflags2 = LK_EXCLUSIVE;
+ if (vp2_locked && VOP_ISLOCKED(vp2) != LK_EXCLUSIVE) {
+ ASSERT_VOP_LOCKED(vp2, "vp2");
+ if (lkflags2 == LK_EXCLUSIVE) {
+ VOP_UNLOCK(vp2);
+ ASSERT_VOP_UNLOCKED(vp2,
+ "vp2 shared recursed");
+ vp2_locked = false;
+ }
+ } else if (!vp2_locked)
ASSERT_VOP_UNLOCKED(vp2, "vp2");
} else {
vp2_locked = true;
}
+
if (!vp1_locked && !vp2_locked) {
- vn_lock(vp1, LK_EXCLUSIVE | LK_RETRY);
+ vn_lock(vp1, lkflags1 | LK_RETRY);
vp1_locked = true;
}
- for (;;) {
- if (vp1_locked && vp2_locked)
- break;
+ while (!vp1_locked || !vp2_locked) {
if (vp1_locked && vp2 != NULL) {
if (vp1 != NULL) {
- error = VOP_LOCK1(vp2, LK_EXCLUSIVE | LK_NOWAIT,
+ error = VOP_LOCK1(vp2, lkflags2 | LK_NOWAIT,
__FILE__, __LINE__);
if (error == 0)
break;
@@ -3804,12 +3828,12 @@ vn_lock_pair(struct vnode *vp1, bool vp1_locked, struct vnode *vp2,
vp1_locked = false;
vn_lock_pair_pause("vlp1");
}
- vn_lock(vp2, LK_EXCLUSIVE | LK_RETRY);
+ vn_lock(vp2, lkflags2 | LK_RETRY);
vp2_locked = true;
}
if (vp2_locked && vp1 != NULL) {
if (vp2 != NULL) {
- error = VOP_LOCK1(vp1, LK_EXCLUSIVE | LK_NOWAIT,
+ error = VOP_LOCK1(vp1, lkflags1 | LK_NOWAIT,
__FILE__, __LINE__);
if (error == 0)
break;
@@ -3817,14 +3841,22 @@ vn_lock_pair(struct vnode *vp1, bool vp1_locked, struct vnode *vp2,
vp2_locked = false;
vn_lock_pair_pause("vlp2");
}
- vn_lock(vp1, LK_EXCLUSIVE | LK_RETRY);
+ vn_lock(vp1, lkflags1 | LK_RETRY);
vp1_locked = true;
}
}
- if (vp1 != NULL)
- ASSERT_VOP_ELOCKED(vp1, "vp1 ret");
- if (vp2 != NULL)
- ASSERT_VOP_ELOCKED(vp2, "vp2 ret");
+ if (vp1 != NULL) {
+ if (lkflags1 == LK_EXCLUSIVE)
+ ASSERT_VOP_ELOCKED(vp1, "vp1 ret");
+ else
+ ASSERT_VOP_LOCKED(vp1, "vp1 ret");
+ }
+ if (vp2 != NULL) {
+ if (lkflags2 == LK_EXCLUSIVE)
+ ASSERT_VOP_ELOCKED(vp2, "vp2 ret");
+ else
+ ASSERT_VOP_LOCKED(vp2, "vp2 ret");
+ }
}
int
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index 74514654713a..5e3f81de0236 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -757,8 +757,8 @@ bool vn_isdisk_error(struct vnode *vp, int *errp);
bool vn_isdisk(struct vnode *vp);
int _vn_lock(struct vnode *vp, int flags, const char *file, int line);
#define vn_lock(vp, flags) _vn_lock(vp, flags, __FILE__, __LINE__)
-void vn_lock_pair(struct vnode *vp1, bool vp1_locked, struct vnode *vp2,
- bool vp2_locked);
+void vn_lock_pair(struct vnode *vp1, bool vp1_locked, int lkflags1,
+ struct vnode *vp2, bool vp2_locked, int lkflags2);
int vn_open(struct nameidata *ndp, int *flagp, int cmode, struct file *fp);
int vn_open_cred(struct nameidata *ndp, int *flagp, int cmode,
u_int vn_open_flags, struct ucred *cred, struct file *fp);
diff --git a/sys/ufs/ffs/ffs_softdep.c b/sys/ufs/ffs/ffs_softdep.c
index 1e245d82f8b8..9f3644477038 100644
--- a/sys/ufs/ffs/ffs_softdep.c
+++ b/sys/ufs/ffs/ffs_softdep.c
@@ -3323,7 +3323,7 @@ softdep_prelink(struct vnode *dvp,
if (vp != NULL) {
VOP_UNLOCK(dvp);
ffs_syncvnode(vp, MNT_NOWAIT, 0);
- vn_lock_pair(dvp, false, vp, true);
+ vn_lock_pair(dvp, false, LK_EXCLUSIVE, vp, true, LK_EXCLUSIVE);
if (dvp->v_data == NULL)
goto out;
}
@@ -3335,7 +3335,8 @@ softdep_prelink(struct vnode *dvp,
VOP_UNLOCK(dvp);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
if (vp->v_data == NULL) {
- vn_lock_pair(dvp, false, vp, true);
+ vn_lock_pair(dvp, false, LK_EXCLUSIVE, vp, true,
+ LK_EXCLUSIVE);
goto out;
}
ACQUIRE_LOCK(ump);
@@ -3345,7 +3346,8 @@ softdep_prelink(struct vnode *dvp,
VOP_UNLOCK(vp);
vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
if (dvp->v_data == NULL) {
- vn_lock_pair(dvp, true, vp, false);
+ vn_lock_pair(dvp, true, LK_EXCLUSIVE, vp, false,
+ LK_EXCLUSIVE);
goto out;
}
}
@@ -3360,7 +3362,7 @@ softdep_prelink(struct vnode *dvp,
journal_check_space(ump);
FREE_LOCK(ump);
- vn_lock_pair(dvp, false, vp, false);
+ vn_lock_pair(dvp, false, LK_EXCLUSIVE, vp, false, LK_EXCLUSIVE);
out:
ndp->ni_dvp_seqc = vn_seqc_read_any(dvp);
if (vp != NULL)
diff --git a/sys/ufs/ufs/ufs_vnops.c b/sys/ufs/ufs/ufs_vnops.c
index 0a34eee310b4..1982e183ca04 100644
--- a/sys/ufs/ufs/ufs_vnops.c
+++ b/sys/ufs/ufs/ufs_vnops.c
@@ -235,7 +235,7 @@ ufs_sync_nlink(struct vnode *vp, struct vnode *vp1)
if (vp1 != NULL)
VOP_UNLOCK(vp1);
error = ufs_sync_nlink1(mp);
- vn_lock_pair(vp, false, vp1, false);
+ vn_lock_pair(vp, false, LK_EXCLUSIVE, vp1, false, LK_EXCLUSIVE);
return (error);
}