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Simplify/fix dnode_move() for dn_zfetch 

Previous code tried to keep prefetch streams while moving dnode.  But
it was at least not updating per-stream zs_fetchback pointers, causing
use-after-free on next access.  Instead of that I see much easier and
cleaner to just drop old prefetch state and start new from scratch.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored-By: iXsystems, Inc.
Closes #11936
Closes #11998
This commit is contained in:
Alexander Motin 2021-05-07 18:07:03 -04:00 committed by Brian Behlendorf
parent 85071b2ff5
commit 0db64e9036
1 changed files with 1 additions and 7 deletions
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8
module/zfs/dnode.c
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@ -754,7 +754,6 @@ dnode_move_impl(dnode_t *odn, dnode_t *ndn)
ASSERT(!RW_LOCK_HELD(&odn->dn_struct_rwlock));
ASSERT(MUTEX_NOT_HELD(&odn->dn_mtx));
ASSERT(MUTEX_NOT_HELD(&odn->dn_dbufs_mtx));
ASSERT(!MUTEX_HELD(&odn->dn_zfetch.zf_lock));
/* Copy fields. */
ndn->dn_objset = odn->dn_objset;
@ -822,9 +821,7 @@ dnode_move_impl(dnode_t *odn, dnode_t *ndn)
ndn->dn_newgid = odn->dn_newgid;
ndn->dn_newprojid = odn->dn_newprojid;
ndn->dn_id_flags = odn->dn_id_flags;
dmu_zfetch_init(&ndn->dn_zfetch, NULL);
list_move_tail(&ndn->dn_zfetch.zf_stream, &odn->dn_zfetch.zf_stream);
ndn->dn_zfetch.zf_dnode = odn->dn_zfetch.zf_dnode;
dmu_zfetch_init(&ndn->dn_zfetch, ndn);
/*
* Update back pointers. Updating the handle fixes the back pointer of
@ -832,9 +829,6 @@ dnode_move_impl(dnode_t *odn, dnode_t *ndn)
*/
ASSERT(ndn->dn_handle->dnh_dnode == odn);
ndn->dn_handle->dnh_dnode = ndn;
if (ndn->dn_zfetch.zf_dnode == odn) {
ndn->dn_zfetch.zf_dnode = ndn;
}
/*
* Invalidate the original dnode by clearing all of its back pointers.