From nobody Wed Dec 08 00:12:46 2021 X-Original-To: dev-commits-src-main@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 20D2518C34FD; Wed, 8 Dec 2021 00:12:48 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4J7yKq1XZXz4YPv; Wed, 8 Dec 2021 00:12:47 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id CBD01D7F; Wed, 8 Dec 2021 00:12:46 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.16.1/8.16.1) with ESMTP id 1B80CkVL029125; Wed, 8 Dec 2021 00:12:46 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 1B80CkCw029124; Wed, 8 Dec 2021 00:12:46 GMT (envelope-from git) Date: Wed, 8 Dec 2021 00:12:46 GMT Message-Id: <202112080012.1B80CkCw029124@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: "Jason A. Harmening" Subject: git: cfc2cfeca195 - main - unionfs: implement VOP_VPUT_PAIR List-Id: Commit messages for the main branch of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-main List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-dev-commits-src-main@freebsd.org X-BeenThere: dev-commits-src-main@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: jah X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: cfc2cfeca195c9ad4a4b50aaf87b466cb9458f05 Auto-Submitted: auto-generated ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1638922367; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=+B/tC8TvfTmbVW/49OkgdQdkOSPDMl1QgZ+gJU+peS4=; b=qmf/XX8e3Ah5hH9Fi2RbsveGgneh8MZsP+gwKm9qoqr7mQDz3RuskZfD51BdpzAtkj9Pn9 PV6h4edDQrPBu35HBngv7cGmOqj/K4iO1PdkJgFN48etCij3JdfDgdhRBV/xUwjyFB8HpE nR7VJaLfV4lg7PcWckpbF+X5YlOuWvkGALgENsvtggeuDaJMiUGSL+jTI9ZUuJHhis6AFE fAsta2sC2D5WJcEPk0MjbAKPw5A5/ovy6LMD1+ASsbGYqbygneGY6rkPxIEluyzjVVwLYr OnkK36AvLcuI+AOlFjAvNJym3BILFOb1YhgXgmJvAZZVxvJhtn3eZ0PnhbX+QQ== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1638922367; a=rsa-sha256; cv=none; b=bU/IMOSgJpnvpzXy7wCXuWm68FGKg1ryx4OxLDkz/CFrI6LDQs5BCzGrJ14WaqtJ/8k+cx 000LuSSlOfcGiBpCQl/RCNBQ5BwPfWM4SiWqJuunZAR9pgd7IXhPAT+J5tnbb3gC8Vth/b XA777IZM40B/FWb6M7FZfWje8CpdJ4SLtCvOCOXxHQlzF+Yh3WZa5WrkzBdTEdTEOaZ06l lOUikEb+vbt9Wbl3pob+NZr7PEeMSfhQycYeBomjqvP/JXO3PPdT+d6hoqjohfXuBVsDoI hEYbzjxHJKSCOKkO3iDIK6Gg0RDTeZ/dR3fJMC2j0JDsxW08Hcu4H4VkAeJcig== ARC-Authentication-Results: i=1; mx1.freebsd.org; none X-ThisMailContainsUnwantedMimeParts: N The branch main has been updated by jah: URL: https://cgit.FreeBSD.org/src/commit/?id=cfc2cfeca195c9ad4a4b50aaf87b466cb9458f05 commit cfc2cfeca195c9ad4a4b50aaf87b466cb9458f05 Author: Jason A. Harmening AuthorDate: 2021-11-15 16:45:20 +0000 Commit: Jason A. Harmening CommitDate: 2021-12-08 00:20:02 +0000 unionfs: implement VOP_VPUT_PAIR unionfs must pass VOP_VPUT_PAIR directly to the underlying FS so that it can have a chance to manage any special locking considerations that may be necessary. The unionfs implementation is based heavily on the corresponding nullfs implementation. Also note some outstanding issues with the unionfs locking scheme, as a first step in fixing those issues in a future change. Discussed with: kib Tested by: pho Differential Revision: https://reviews.freebsd.org/D33008 --- sys/fs/unionfs/union_vnops.c | 133 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 133 insertions(+) diff --git a/sys/fs/unionfs/union_vnops.c b/sys/fs/unionfs/union_vnops.c index 381e413e18ba..ef0c4300ff0b 100644 --- a/sys/fs/unionfs/union_vnops.c +++ b/sys/fs/unionfs/union_vnops.c @@ -1868,6 +1868,16 @@ unionfs_lock(struct vop_lock1_args *ap) KASSERT_UNIONFS_VNODE(ap->a_vp); + /* + * TODO: rework the unionfs locking scheme. + * It's not guaranteed to be safe to blindly lock two vnodes on + * different mounts as is done here. Further, the entanglement + * of locking both vnodes with the various options that can be + * passed to VOP_LOCK() makes this code hard to reason about. + * Instead, consider locking only the upper vnode, or the lower + * vnode is the upper is not present, and taking separate measures + * to lock both vnodes in the few cases when that is needed. + */ error = 0; interlock = 1; uhold = 0; @@ -2535,6 +2545,128 @@ unionfs_add_writecount(struct vop_add_writecount_args *ap) return (error); } +static int +unionfs_vput_pair(struct vop_vput_pair_args *ap) +{ + struct mount *mp; + struct vnode *dvp, *vp, **vpp, *lvp, *ldvp, *uvp, *udvp, *tempvp; + struct unionfs_node *dunp, *unp; + int error, res; + + dvp = ap->a_dvp; + vpp = ap->a_vpp; + vp = NULLVP; + lvp = NULLVP; + uvp = NULLVP; + unp = NULL; + + dunp = VTOUNIONFS(dvp); + udvp = dunp->un_uppervp; + ldvp = dunp->un_lowervp; + + /* + * Underlying vnodes should be locked because the encompassing unionfs + * node is locked, but will not be referenced, as the reference will + * only be on the unionfs node. Reference them now so that the vput()s + * performed by VOP_VPUT_PAIR() will have a reference to drop. + */ + if (udvp != NULLVP) + vref(udvp); + if (ldvp != NULLVP) + vref(ldvp); + + if (vpp != NULL) + vp = *vpp; + + if (vp != NULLVP) { + unp = VTOUNIONFS(vp); + uvp = unp->un_uppervp; + lvp = unp->un_lowervp; + if (uvp != NULLVP) + vref(uvp); + if (lvp != NULLVP) + vref(lvp); + + /* + * If we're being asked to return a locked child vnode, then + * we may need to create a replacement vnode in case the + * original is reclaimed while the lock is dropped. In that + * case we'll need to ensure the mount and the underlying + * vnodes aren't also recycled during that window. + */ + if (!ap->a_unlock_vp) { + vhold(vp); + if (uvp != NULLVP) + vhold(uvp); + if (lvp != NULLVP) + vhold(lvp); + mp = vp->v_mount; + vfs_ref(mp); + } + } + + /* + * TODO: Because unionfs_lock() locks both the lower and upper vnodes + * (if available), we must also call VOP_VPUT_PAIR() on both the lower + * and upper parent/child pairs. If unionfs_lock() is reworked to lock + * only a single vnode, this code will need to change to also only + * operate on one vnode pair. + */ + ASSERT_VOP_LOCKED(ldvp, __func__); + ASSERT_VOP_LOCKED(udvp, __func__); + ASSERT_VOP_LOCKED(lvp, __func__); + ASSERT_VOP_LOCKED(uvp, __func__); + + KASSERT(lvp == NULLVP || ldvp != NULLVP, + ("%s: NULL ldvp with non-NULL lvp", __func__)); + if (ldvp != NULLVP) + res = VOP_VPUT_PAIR(ldvp, lvp != NULLVP ? &lvp : NULL, true); + KASSERT(uvp == NULLVP || udvp != NULLVP, + ("%s: NULL udvp with non-NULL uvp", __func__)); + if (udvp != NULLVP) + res = VOP_VPUT_PAIR(udvp, uvp != NULLVP ? &uvp : NULL, true); + + ASSERT_VOP_UNLOCKED(ldvp, __func__); + ASSERT_VOP_UNLOCKED(udvp, __func__); + ASSERT_VOP_UNLOCKED(lvp, __func__); + ASSERT_VOP_UNLOCKED(uvp, __func__); + + /* + * VOP_VPUT_PAIR() dropped the references we added to the underlying + * vnodes, now drop the caller's reference to the unionfs vnodes. + */ + if (vp != NULLVP && ap->a_unlock_vp) + vrele(vp); + vrele(dvp); + + if (vp == NULLVP || ap->a_unlock_vp) + return (res); + + /* + * We're being asked to return a locked vnode. At this point, the + * underlying vnodes have been unlocked, so vp may have been reclaimed. + */ + vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); + if (vp->v_data == NULL && vfs_busy(mp, MBF_NOWAIT) == 0) { + vput(vp); + error = unionfs_nodeget(mp, uvp, lvp, dvp, &tempvp, NULL); + if (error == 0) { + vn_lock(tempvp, LK_EXCLUSIVE | LK_RETRY); + *vpp = tempvp; + } else + vget(vp, LK_EXCLUSIVE | LK_RETRY); + vfs_unbusy(mp); + } + if (lvp != NULLVP) + vdrop(lvp); + if (uvp != NULLVP) + vdrop(uvp); + vdrop(vp); + vfs_rel(mp); + + return (res); +} + struct vop_vector unionfs_vnodeops = { .vop_default = &default_vnodeops, @@ -2585,5 +2717,6 @@ struct vop_vector unionfs_vnodeops = { .vop_write = unionfs_write, .vop_vptofh = unionfs_vptofh, .vop_add_writecount = unionfs_add_writecount, + .vop_vput_pair = unionfs_vput_pair, }; VFS_VOP_VECTOR_REGISTER(unionfs_vnodeops);