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

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Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D29769
This commit is contained in:
Mateusz Guzik 2021-04-15 09:54:18 +02:00
parent 54f98c4dbf
commit 9c651561a2
1 changed files with 21 additions and 0 deletions
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21
sys/contrib/openzfs/module/os/freebsd/zfs/zfs_vnops_os.c
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@ -781,6 +781,7 @@ 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;
seqc_t dvp_seqc;
int error = 0;
/*
@ -806,6 +807,8 @@ zfs_lookup(vnode_t *dvp, const char *nm, vnode_t **vpp,
ZFS_ENTER(zfsvfs);
ZFS_VERIFY_ZP(zdp);
dvp_seqc = vn_seqc_read_any(dvp);
*vpp = NULL;
if (flags & LOOKUP_XATTR) {
@ -975,6 +978,24 @@ zfs_lookup(vnode_t *dvp, const char *nm, vnode_t **vpp,
}
}
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;
}
}
/* Insert name into cache (as non-existent) if appropriate. */
if (zfsvfs->z_use_namecache && !zfsvfs->z_replay &&
error == ENOENT && (cnp->cn_flags & MAKEENTRY) != 0)