dmu_objset: release bonus buffer in failure path

Reported by kmemleak during testing of a new patch:

```
unreferenced object 0xffff9f1c12e38800 (size 1024):
  comm "z_upgrade", pid 17842, jiffies 4296870904 (age 8746.268s)
  backtrace:
    kmemleak_alloc+0x7a/0x100
    __kmalloc_node+0x26c/0x510
    range_tree_create+0x39/0xa0 [zfs]
    dmu_zfetch_init+0x73/0xe0 [zfs]
    dnode_create+0x12c/0x3b0 [zfs]
    dnode_hold_impl+0x1096/0x1130 [zfs]
    dnode_hold+0x23/0x30 [zfs]
    dmu_bonus_hold_impl+0x6b/0x370 [zfs]
    dmu_bonus_hold+0x1e/0x30 [zfs]
    dmu_objset_space_upgrade+0x114/0x310 [zfs]
    dmu_objset_userobjspace_upgrade_cb+0xd8/0x150 [zfs]
    dmu_objset_upgrade_task_cb+0x136/0x1e0 [zfs]
    kthread+0x119/0x150
```

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Signed-off-by: Gvozden Neskovic <neskovic@gmail.com>
Closes #6575

diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c
index 3faa299d1eac9a61bcb8e4018c660ae96a2f555c..4445121a0664e97fac312914d42079b6a71f1c3d 100644 (file)
--- a/module/zfs/dmu_objset.c
+++ b/module/zfs/dmu_objset.c
@@ -2032,6 +2032,7 @@ dmu_objset_space_upgrade(objset_t *os)
                dmu_tx_hold_bonus(tx, obj);
                objerr = dmu_tx_assign(tx, TXG_WAIT);
                if (objerr != 0) {
+                       dmu_buf_rele(db, FTAG);
                        dmu_tx_abort(tx);
                        continue;
                }