[FreeBSD] zfs_znode_alloc: lock the vnode earlier

This is needed because of a possible error path where zfs_vnode_forget()
is called.  That function calls vgone() and vput(), the former requires
the vnode to be exclusively locked and the latter expects it to be
locked.

It should be safe to lock the vnode as early as possible because it is
not yet visible, so there is no interaction with other locks.

While here, remove a tautological assignment to 'vp'.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Signed-off-by: Andriy Gapon <avg@FreeBSD.org>
Closes #14565

diff --git a/module/os/freebsd/zfs/zfs_znode.c b/module/os/freebsd/zfs/zfs_znode.c
index 76ae09f811ebf63d5ff34aae9937ebe63b39615f..304bc71f90dbd4afcffce4ed925e19fca953b80c 100644 (file)
--- a/module/os/freebsd/zfs/zfs_znode.c
+++ b/module/os/freebsd/zfs/zfs_znode.c
@@ -448,6 +448,13 @@ zfs_znode_alloc(zfsvfs_t *zfsvfs, dmu_buf_t *db, int blksz,
        zp->z_vnode = vp;
        vp->v_data = zp;
 
+       /*
+        * Acquire the vnode lock before any possible interaction with the
+        * outside world.  Specifically, there is an error path that calls
+        * zfs_vnode_forget() and the vnode should be exclusively locked.
+        */
+       vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+
        ASSERT(!POINTER_IS_VALID(zp->z_zfsvfs));
 
        zp->z_sa_hdl = NULL;
@@ -464,8 +471,6 @@ zfs_znode_alloc(zfsvfs_t *zfsvfs, dmu_buf_t *db, int blksz,
        atomic_store_ptr(&zp->z_cached_symlink, NULL);
 #endif
 
-       vp = ZTOV(zp);
-
        zfs_znode_sa_init(zfsvfs, zp, db, obj_type, hdl);
 
        SA_ADD_BULK_ATTR(bulk, count, SA_ZPL_MODE(zfsvfs), NULL, &mode, 8);
@@ -535,10 +540,6 @@ zfs_znode_alloc(zfsvfs_t *zfsvfs, dmu_buf_t *db, int blksz,
        zp->z_zfsvfs = zfsvfs;
        mutex_exit(&zfsvfs->z_znodes_lock);
 
-       /*
-        * Acquire vnode lock before making it available to the world.
-        */
-       vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 #if __FreeBSD_version >= 1400077
        vn_set_state(vp, VSTATE_CONSTRUCTED);
 #endif