diff options
| author | John Poduska <[email protected]> | 2020-03-12 13:25:56 -0400 |
|---|---|---|
| committer | GitHub <[email protected]> | 2020-03-12 10:25:56 -0700 |
| commit | e6b28efccc4853b4f2715c2d37ab05cead2e1c3e (patch) | |
| tree | 106de4649fcdb96798b03a92309b1e9ffa9540ef /module | |
| parent | 1e9231ada893d43bdbfa8ef3a11f1e423296981d (diff) | |
Prevent race condition in dnode_dest (#10101)
dnode_special_close() waits for the refcount of dn_holds to go to zero
without holding the dn_mtx. dnode_rele_and_unlock() does the final
remove to dn_holds with dn_mtx being held:
refs = zfs_refcount_remove(&dn->dn_holds, tag);
mutex_exit(&dn->dn_mtx);
So, there is a race condition after the remove until dn_mtx is
dropped. During that time, dnode_destroy() can get called, which ends
up in dnode_dest() calling mutex_destroy() and a panic since the lock
is still held.
This change adds a condvar to wait for the final dnode_rele_and_unlock()
to release the dn_mtx before calling dnode_destroy().
Reviewed-by: Paul Dagnelie <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Matthew Ahrens <[email protected]>
Signed-off-by: John Poduska <[email protected]>
Closes #7814
Closes #10101
Diffstat (limited to 'module')
| -rw-r--r-- | module/zfs/dnode.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/module/zfs/dnode.c b/module/zfs/dnode.c index 5a3de232c..138f50630 100644 --- a/module/zfs/dnode.c +++ b/module/zfs/dnode.c @@ -119,6 +119,7 @@ dnode_cons(void *arg, void *unused, int kmflag) mutex_init(&dn->dn_mtx, NULL, MUTEX_DEFAULT, NULL); mutex_init(&dn->dn_dbufs_mtx, NULL, MUTEX_DEFAULT, NULL); cv_init(&dn->dn_notxholds, NULL, CV_DEFAULT, NULL); + cv_init(&dn->dn_nodnholds, NULL, CV_DEFAULT, NULL); /* * Every dbuf has a reference, and dropping a tracked reference is @@ -183,6 +184,7 @@ dnode_dest(void *arg, void *unused) mutex_destroy(&dn->dn_mtx); mutex_destroy(&dn->dn_dbufs_mtx); cv_destroy(&dn->dn_notxholds); + cv_destroy(&dn->dn_nodnholds); zfs_refcount_destroy(&dn->dn_holds); zfs_refcount_destroy(&dn->dn_tx_holds); ASSERT(!list_link_active(&dn->dn_link)); @@ -1171,13 +1173,15 @@ dnode_special_close(dnode_handle_t *dnh) dnode_t *dn = dnh->dnh_dnode; /* - * Wait for final references to the dnode to clear. This can - * only happen if the arc is asynchronously evicting state that - * has a hold on this dnode while we are trying to evict this - * dnode. + * Ensure dnode_rele_and_unlock() has released dn_mtx, after final + * zfs_refcount_remove() */ - while (zfs_refcount_count(&dn->dn_holds) > 0) - delay(1); + mutex_enter(&dn->dn_mtx); + if (zfs_refcount_count(&dn->dn_holds) > 0) + cv_wait(&dn->dn_nodnholds, &dn->dn_mtx); + mutex_exit(&dn->dn_mtx); + ASSERT3U(zfs_refcount_count(&dn->dn_holds), ==, 0); + ASSERT(dn->dn_dbuf == NULL || dmu_buf_get_user(&dn->dn_dbuf->db) == NULL); zrl_add(&dnh->dnh_zrlock); @@ -1606,7 +1610,10 @@ dnode_rele_and_unlock(dnode_t *dn, void *tag, boolean_t evicting) dnode_handle_t *dnh = dn->dn_handle; refs = zfs_refcount_remove(&dn->dn_holds, tag); + if (refs == 0) + cv_broadcast(&dn->dn_nodnholds); mutex_exit(&dn->dn_mtx); + /* dnode could get destroyed at this point, so don't use it anymore */ /* * It's unsafe to release the last hold on a dnode by dnode_rele() or |