From a78a93e67e883db4d984bf673d1155a6906999fc Mon Sep 17 00:00:00 2001 From: Mateusz Guzik Date: Mon, 26 Apr 2021 21:44:40 +0200 Subject: [PATCH] FreeBSD: damage control racing .. lookups in face of mkdir/rmdir External-issue: https://reviews.freebsd.org/D29769 Reviewed-by: Alexander Motin Reviewed-by: Ryan Moeller Signed-off-by: Mateusz Guzik Closes #11926 --- module/os/freebsd/zfs/zfs_vnops_os.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/module/os/freebsd/zfs/zfs_vnops_os.c b/module/os/freebsd/zfs/zfs_vnops_os.c index eb72f294d5..be8ac1fc6c 100644 --- a/module/os/freebsd/zfs/zfs_vnops_os.c +++ b/module/os/freebsd/zfs/zfs_vnops_os.c @@ -1013,6 +1013,9 @@ zfs_lookup(vnode_t *dvp, const char *nm, vnode_t **vpp, znode_t *zdp = VTOZ(dvp); znode_t *zp; zfsvfs_t *zfsvfs = zdp->z_zfsvfs; +#if __FreeBSD_version > 1300124 + seqc_t dvp_seqc; +#endif int error = 0; /* @@ -1038,6 +1041,10 @@ zfs_lookup(vnode_t *dvp, const char *nm, vnode_t **vpp, ZFS_ENTER(zfsvfs); ZFS_VERIFY_ZP(zdp); +#if __FreeBSD_version > 1300124 + dvp_seqc = vn_seqc_read_notmodify(dvp); +#endif + *vpp = NULL; if (flags & LOOKUP_XATTR) { @@ -1207,6 +1214,26 @@ zfs_lookup(vnode_t *dvp, const char *nm, vnode_t **vpp, } } +#if __FreeBSD_version > 1300124 + if ((cnp->cn_flags & ISDOTDOT) != 0) { + /* + * FIXME: zfs_lookup_lock relocks vnodes and does nothing to + * handle races. In particular different callers may end up + * with different vnodes and will try to add conflicting + * entries to the namecache. + * + * While finding different result may be acceptable in face + * of concurrent modification, adding conflicting entries + * trips over an assert in the namecache. + * + * Ultimately let an entry through once everything settles. + */ + if (!vn_seqc_consistent(dvp, dvp_seqc)) { + cnp->cn_flags &= ~MAKEENTRY; + } + } +#endif + /* Insert name into cache (as non-existent) if appropriate. */ if (zfsvfs->z_use_namecache && !zfsvfs->z_replay && error == ENOENT && (cnp->cn_flags & MAKEENTRY) != 0)