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vn_lock_pair(): allow to request shared locking

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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
This commit is contained in:
Konstantin Belousov 2023-04-06 07:11:08 +03:00
parent d6e2490134
commit bb24eaea49
6 changed files with 71 additions and 36 deletions
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3
sys/fs/unionfs/union_subr.c
View file

@ -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);

2
sys/kern/vfs_mount.c
View file

@ -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;

86
sys/kern/vfs_vnops.c
View file

@ -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

4
sys/sys/vnode.h
View file

@ -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);

10
sys/ufs/ffs/ffs_softdep.c
View file

@ -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)

2
sys/ufs/ufs/ufs_vnops.c
View file

@ -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);
}