Date: Sun, 18 Feb 2024 15:18:20 GMT From: "Jason A. Harmening" <jah@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 2656fc29be8b - main - unionfs: upgrade the vnode lock during fsync() if necessary Message-ID: <202402181518.41IFIKf4009294@gitrepo.freebsd.org>
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The branch main has been updated by jah: URL: https://cgit.FreeBSD.org/src/commit/?id=2656fc29be8b0fc1cd9e64ed52aa0a61fe87744c commit 2656fc29be8b0fc1cd9e64ed52aa0a61fe87744c Author: Jason A. Harmening <jah@FreeBSD.org> AuthorDate: 2023-12-24 04:42:28 +0000 Commit: Jason A. Harmening <jah@FreeBSD.org> CommitDate: 2024-02-18 15:18:07 +0000 unionfs: upgrade the vnode lock during fsync() if necessary If the underlying upper FS supports shared locking for write ops, as is the case with ZFS, VOP_FSYNC() may only be called with the vnode lock held shared. In this case, temporarily upgrade the lock for those unionfs maintenance operations which require exclusive locking. While here, make unionfs inherit the upper FS' support for shared write locking. Since the upper FS is the target of VOP_GETWRITEMOUNT() this is what will dictate the locking behavior of any unionfs caller that uses vn_start_write() + vn_lktype_write(), so unionfs must be prepared for the caller to only hold a shared vnode lock in these cases. Found in local testing of unionfs atop ZFS with DEBUG_VFS_LOCKS. MFC after: 2 weeks Reviewed by: kib, olce Differential Revision: https://reviews.freebsd.org/D43817 --- sys/fs/unionfs/union_vfsops.c | 3 ++- sys/fs/unionfs/union_vnops.c | 8 ++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/sys/fs/unionfs/union_vfsops.c b/sys/fs/unionfs/union_vfsops.c index 8635600549b1..cb55c2dd6474 100644 --- a/sys/fs/unionfs/union_vfsops.c +++ b/sys/fs/unionfs/union_vfsops.c @@ -348,7 +348,8 @@ unionfs_domount(struct mount *mp) if ((ump->um_lowermp->mnt_flag & MNT_LOCAL) != 0 && (ump->um_uppermp->mnt_flag & MNT_LOCAL) != 0) mp->mnt_flag |= MNT_LOCAL; - mp->mnt_kern_flag |= MNTK_NOMSYNC | MNTK_UNIONFS; + mp->mnt_kern_flag |= MNTK_NOMSYNC | MNTK_UNIONFS | + (ump->um_uppermp->mnt_kern_flag & MNTK_SHARED_WRITES); MNT_IUNLOCK(mp); /* diff --git a/sys/fs/unionfs/union_vnops.c b/sys/fs/unionfs/union_vnops.c index cb2bed925399..3ea427b5b53c 100644 --- a/sys/fs/unionfs/union_vnops.c +++ b/sys/fs/unionfs/union_vnops.c @@ -998,14 +998,22 @@ unionfs_fsync(struct vop_fsync_args *ap) struct unionfs_node *unp; struct unionfs_node_status *unsp; struct vnode *ovp; + enum unionfs_lkupgrade lkstatus; KASSERT_UNIONFS_VNODE(ap->a_vp); unp = VTOUNIONFS(ap->a_vp); + lkstatus = unionfs_upgrade_lock(ap->a_vp); + if (lkstatus == UNIONFS_LKUPGRADE_DOOMED) { + unionfs_downgrade_lock(ap->a_vp, lkstatus); + return (ENOENT); + } unionfs_get_node_status(unp, ap->a_td, &unsp); ovp = (unsp->uns_upper_opencnt ? unp->un_uppervp : unp->un_lowervp); unionfs_tryrem_node_status(unp, unsp); + unionfs_downgrade_lock(ap->a_vp, lkstatus); + if (ovp == NULLVP) return (EBADF);
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