The branch main has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=aeabf8d4b9727201648887f8aa7dd1930cf0e154
commit aeabf8d4b9727201648887f8aa7dd1930cf0e154 Author: Mateusz Guzik <[email protected]> AuthorDate: 2022-03-07 11:43:43 +0000 Commit: Mateusz Guzik <[email protected]> CommitDate: 2022-03-19 10:47:10 +0000 nullfs: hash insertion without vnode lock upgrade Use the hash lock to serialize instead. This enables shared-locked ".." lookups. Reviewed by: markj Tested by: pho (previous version) Differential Revision: https://reviews.freebsd.org/D34466 --- sys/fs/nullfs/null_subr.c | 114 ++++++++++++++++++++------------------------ sys/fs/nullfs/null_vfsops.c | 2 +- 2 files changed, 53 insertions(+), 63 deletions(-) diff --git a/sys/fs/nullfs/null_subr.c b/sys/fs/nullfs/null_subr.c index 6b422410b9ec..b2b6e6837b2d 100644 --- a/sys/fs/nullfs/null_subr.c +++ b/sys/fs/nullfs/null_subr.c @@ -65,7 +65,7 @@ static u_long null_hash_mask; static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table"); MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part"); -static struct vnode * null_hashins(struct mount *, struct null_node *); +static void null_hashins(struct mount *, struct null_node *); /* * Initialise cache headers @@ -93,14 +93,15 @@ nullfs_uninit(struct vfsconf *vfsp) * Return a VREF'ed alias for lower vnode if already exists, else 0. * Lower vnode should be locked on entry and will be left locked on exit. */ -struct vnode * -null_hashget(struct mount *mp, struct vnode *lowervp) +static struct vnode * +null_hashget_locked(struct mount *mp, struct vnode *lowervp) { struct null_node_hashhead *hd; struct null_node *a; struct vnode *vp; ASSERT_VOP_LOCKED(lowervp, "null_hashget"); + rw_assert(&null_hash_lock, RA_LOCKED); /* * Find hash base, and then search the (two-way) linked @@ -109,9 +110,6 @@ null_hashget(struct mount *mp, struct vnode *lowervp) * reference count (but NOT the lower vnode's VREF counter). */ hd = NULL_NHASH(lowervp); - if (LIST_EMPTY(hd)) - return (NULLVP); - rw_rlock(&null_hash_lock); LIST_FOREACH(a, hd, null_hash) { if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) { /* @@ -122,43 +120,50 @@ null_hashget(struct mount *mp, struct vnode *lowervp) */ vp = NULLTOV(a); vref(vp); - rw_runlock(&null_hash_lock); return (vp); } } - rw_runlock(&null_hash_lock); return (NULLVP); } -/* - * Act like null_hashget, but add passed null_node to hash if no existing - * node found. - */ -static struct vnode * +struct vnode * +null_hashget(struct mount *mp, struct vnode *lowervp) +{ + struct null_node_hashhead *hd; + struct vnode *vp; + + hd = NULL_NHASH(lowervp); + if (LIST_EMPTY(hd)) + return (NULLVP); + + rw_rlock(&null_hash_lock); + vp = null_hashget_locked(mp, lowervp); + rw_runlock(&null_hash_lock); + + return (vp); +} + +static void null_hashins(struct mount *mp, struct null_node *xp) { struct null_node_hashhead *hd; +#ifdef INVARIANTS struct null_node *oxp; - struct vnode *ovp; +#endif + + rw_assert(&null_hash_lock, RA_WLOCKED); hd = NULL_NHASH(xp->null_lowervp); - rw_wlock(&null_hash_lock); +#ifdef INVARIANTS LIST_FOREACH(oxp, hd, null_hash) { if (oxp->null_lowervp == xp->null_lowervp && NULLTOV(oxp)->v_mount == mp) { - /* - * See null_hashget for a description of this - * operation. - */ - ovp = NULLTOV(oxp); - vref(ovp); - rw_wunlock(&null_hash_lock); - return (ovp); + VNASSERT(0, NULLTOV(oxp), + ("vnode already in hash")); } } +#endif LIST_INSERT_HEAD(hd, xp, null_hash); - rw_wunlock(&null_hash_lock); - return (NULLVP); } static void @@ -201,19 +206,6 @@ null_nodeget(struct mount *mp, struct vnode *lowervp, struct vnode **vpp) return (0); } - /* - * The insmntque1() call below requires the exclusive lock on - * the nullfs vnode. Upgrade the lock now if hash failed to - * provide ready to use vnode. - */ - if (VOP_ISLOCKED(lowervp) != LK_EXCLUSIVE) { - vn_lock(lowervp, LK_UPGRADE | LK_RETRY); - if (VN_IS_DOOMED(lowervp)) { - vput(lowervp); - return (ENOENT); - } - } - /* * We do not serialize vnode creation, instead we will check for * duplicates later, when adding new vnode to hash. @@ -229,20 +221,23 @@ null_nodeget(struct mount *mp, struct vnode *lowervp, struct vnode **vpp) return (error); } + VNPASS(vp->v_object == NULL, vp); + VNPASS((vn_irflag_read(vp) & VIRF_PGREAD) == 0, vp); + + rw_wlock(&null_hash_lock); xp->null_vnode = vp; xp->null_lowervp = lowervp; xp->null_flags = 0; vp->v_type = lowervp->v_type; vp->v_data = xp; vp->v_vnlock = lowervp->v_vnlock; - error = insmntque1(vp, mp); - if (error != 0) { - vput(lowervp); + *vpp = null_hashget_locked(mp, lowervp); + if (*vpp != NULL) { + rw_wunlock(&null_hash_lock); + vrele(lowervp); null_destroy_proto(vp, xp); - return (error); + return (0); } - if (lowervp == MOUNTTONULLMOUNT(mp)->nullm_lowerrootvp) - vp->v_vflag |= VV_ROOT; /* * We might miss the case where lower vnode sets VIRF_PGREAD @@ -251,28 +246,23 @@ null_nodeget(struct mount *mp, struct vnode *lowervp, struct vnode **vpp) */ if ((vn_irflag_read(lowervp) & VIRF_PGREAD) != 0) { MPASS(lowervp->v_object != NULL); - if ((vn_irflag_read(vp) & VIRF_PGREAD) == 0) { - if (vp->v_object == NULL) - vp->v_object = lowervp->v_object; - else - MPASS(vp->v_object == lowervp->v_object); - vn_irflag_set_cond(vp, VIRF_PGREAD); - } else { - MPASS(vp->v_object != NULL); - } + vp->v_object = lowervp->v_object; + vn_irflag_set(vp, VIRF_PGREAD); } + if (lowervp == MOUNTTONULLMOUNT(mp)->nullm_lowerrootvp) + vp->v_vflag |= VV_ROOT; - /* - * Atomically insert our new node into the hash or vget existing - * if someone else has beaten us to it. - */ - *vpp = null_hashins(mp, xp); - if (*vpp != NULL) { - vrele(lowervp); - vp->v_object = NULL; /* in case VIRF_PGREAD set it */ + error = insmntque1(vp, mp); + if (error != 0) { + rw_wunlock(&null_hash_lock); + vput(lowervp); + vp->v_object = NULL; null_destroy_proto(vp, xp); - return (0); + return (error); } + + null_hashins(mp, xp); + rw_wunlock(&null_hash_lock); *vpp = vp; return (0); diff --git a/sys/fs/nullfs/null_vfsops.c b/sys/fs/nullfs/null_vfsops.c index 1dba5f51d619..21a28dd45570 100644 --- a/sys/fs/nullfs/null_vfsops.c +++ b/sys/fs/nullfs/null_vfsops.c @@ -207,7 +207,7 @@ nullfs_mount(struct mount *mp) (MNTK_SHARED_WRITES | MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED); } - mp->mnt_kern_flag |= MNTK_LOOKUP_EXCL_DOTDOT | MNTK_NOMSYNC; + mp->mnt_kern_flag |= MNTK_NOMSYNC | MNTK_UNLOCKED_INSMNTQUE; mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag & (MNTK_USES_BCACHE | MNTK_NO_IOPF | MNTK_UNMAPPED_BUFS); MNT_IUNLOCK(mp);
