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FreeBSD: damage control racing .. lookups in face of mkdir/rmdir 

External-issue: https://reviews.freebsd.org/D29769
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Closes #11926
This commit is contained in:
Mateusz Guzik 2021-04-26 21:44:40 +02:00 committed by Brian Behlendorf
parent e5c01296ff
commit 1b7d883eaa
1 changed files with 27 additions and 0 deletions
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27
module/os/freebsd/zfs/zfs_vnops_os.c
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@ -781,6 +781,9 @@ 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;
/*
@ -806,6 +809,10 @@ 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) {
@ -975,6 +982,26 @@ 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)