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nullfs: reduce areas protected by vnode interlock

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Some places only take the interlock to hold the vnode, which was a requiremnt
before they started being manipulated with atomics. Use the newly introduced
vholdnz to bump the count.

Reviewed by:	kib
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D21358
This commit is contained in:
Mateusz Guzik 2019-08-25 05:13:15 +00:00
parent 0256405e98
commit 33d46a3cef
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=351472
1 changed files with 4 additions and 21 deletions
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25
sys/fs/nullfs/null_vnops.c
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@ -668,7 +668,7 @@ null_lock(struct vop_lock1_args *ap)
* We prevent it from being recycled by holding the vnode
* here.
*/
vholdl(lvp);
vholdnz(lvp);
error = VOP_LOCK(lvp, flags);
/*
@ -710,31 +710,16 @@ static int
null_unlock(struct vop_unlock_args *ap)
{
struct vnode *vp = ap->a_vp;
int flags = ap->a_flags;
int mtxlkflag = 0;
struct null_node *nn;
struct vnode *lvp;
int error;
if ((flags & LK_INTERLOCK) != 0)
mtxlkflag = 1;
else if (mtx_owned(VI_MTX(vp)) == 0) {
VI_LOCK(vp);
mtxlkflag = 2;
}
nn = VTONULL(vp);
if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) {
VI_LOCK_FLAGS(lvp, MTX_DUPOK);
flags |= LK_INTERLOCK;
vholdl(lvp);
VI_UNLOCK(vp);
error = VOP_UNLOCK(lvp, flags);
vholdnz(lvp);
error = VOP_UNLOCK(lvp, 0);
vdrop(lvp);
if (mtxlkflag == 0)
VI_LOCK(vp);
} else {
if (mtxlkflag == 2)
VI_UNLOCK(vp);
error = vop_stdunlock(ap);
}
@ -845,10 +830,8 @@ null_getwritemount(struct vop_getwritemount_args *ap)
VI_LOCK(vp);
xp = VTONULL(vp);
if (xp && (lowervp = xp->null_lowervp)) {
VI_LOCK_FLAGS(lowervp, MTX_DUPOK);
vholdnz(lowervp);
VI_UNLOCK(vp);
vholdl(lowervp);
VI_UNLOCK(lowervp);
VOP_GETWRITEMOUNT(lowervp, ap->a_mpp);
vdrop(lowervp);
} else {