diff options
| author | Rohan Puri <[email protected]> | 2018-07-28 18:32:12 +0530 |
|---|---|---|
| committer | Brian Behlendorf <[email protected]> | 2018-08-01 15:00:02 -0700 |
| commit | fd7265c646f40e364396af5014bbb83e809e124a (patch) | |
| tree | 4f4d7f280ce699992cbb0224a2951c2eb101d0d4 /module/zfs/zfs_ctldir.c | |
| parent | 492f64e941e3d6b947d1cc387a1a380c0c738b09 (diff) | |
Fix deadlock between zfs umount & snapentry_expire
zfs umount -> zfsctl_destroy() takes the zfs_snapshot_lock as a
writer and calls zfsctl_snapshot_unmount_cancel(), which waits
for snapentry_expire() if present (when snap is automounted).
This snapentry_expire() itself then waits for zfs_snapshot_lock
as a reader, resulting in a deadlock.
The fix is to only hold the zfs_snapshot_lock over the tree
lookup and removal. After a successful lookup the lock can
be dropped and zfs_snapentry_t will remain valid until the
reference taken by the lookup is released.
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Rohan Puri <[email protected]>
Closes #7751
Closes #7752
Diffstat (limited to 'module/zfs/zfs_ctldir.c')
| -rw-r--r-- | module/zfs/zfs_ctldir.c | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/module/zfs/zfs_ctldir.c b/module/zfs/zfs_ctldir.c index baa72863e..8a35c9947 100644 --- a/module/zfs/zfs_ctldir.c +++ b/module/zfs/zfs_ctldir.c @@ -355,8 +355,6 @@ snapentry_expire(void *data) static void zfsctl_snapshot_unmount_cancel(zfs_snapentry_t *se) { - ASSERT(RW_LOCK_HELD(&zfs_snapshot_lock)); - if (taskq_cancel_id(system_delay_taskq, se->se_taskqid) == 0) { se->se_taskqid = TASKQID_INVALID; zfsctl_snapshot_rele(se); @@ -567,13 +565,14 @@ zfsctl_destroy(zfsvfs_t *zfsvfs) uint64_t objsetid = dmu_objset_id(zfsvfs->z_os); rw_enter(&zfs_snapshot_lock, RW_WRITER); - if ((se = zfsctl_snapshot_find_by_objsetid(spa, objsetid)) - != NULL) { - zfsctl_snapshot_unmount_cancel(se); + se = zfsctl_snapshot_find_by_objsetid(spa, objsetid); + if (se != NULL) zfsctl_snapshot_remove(se); + rw_exit(&zfs_snapshot_lock); + if (se != NULL) { + zfsctl_snapshot_unmount_cancel(se); zfsctl_snapshot_rele(se); } - rw_exit(&zfs_snapshot_lock); } else if (zfsvfs->z_ctldir) { iput(zfsvfs->z_ctldir); zfsvfs->z_ctldir = NULL; |