[PATCH][SRU][XENIAL] UBUNTU: SAUCE: (noup) zfs to 0.6.5.6-0ubuntu25
Colin King
colin.king at canonical.com
Thu Jul 12 15:48:19 UTC 2018
From: Colin Ian King <colin.king at canonical.com>
BugLink: http://bugs.launchpad.net/bugs/1781364
This is a sync of zfs 0.6.5.6-0ubuntu25 that fixes a mount/umount deadlock
for upstream ZFS commit ac09630d8b0b ("Fix zpl_mount() deadlock")
ZFS commit 93b43af inadvertently introduced the following scenario which
can result in a deadlock. This issue was most easily reproduced by
LXD containers using a ZFS storage backend but should be reproducible
under any workload which is frequently mounting and unmounting.
-- THREAD A --
spa_sync()
spa_sync_upgrades()
rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG); <- Waiting on B
-- THREAD B --
mount_fs()
zpl_mount()
zpl_mount_impl()
dmu_objset_hold()
dmu_objset_hold_flags()
dsl_pool_hold()
dsl_pool_config_enter()
rrw_enter(&dp->dp_config_rwlock, RW_READER, tag);
sget()
sget_userns()
grab_super()
down_write(&s->s_umount); <- Waiting on C
-- THREAD C --
cleanup_mnt()
deactivate_super()
down_write(&s->s_umount);
deactivate_locked_super()
zpl_kill_sb()
kill_anon_super()
generic_shutdown_super()
sync_filesystem()
zpl_sync_fs()
zfs_sync()
zil_commit()
txg_wait_synced() <- Waiting on A
Signed-off-by: Brian Behlendorf <behlendorf1 at llnl.gov>
(backport from ZFS upstream commit ac09630d8b0bf6c92084a30fdaefd03fd0adbdc1)
Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
zfs/META | 2 +-
zfs/include/sys/zfs_vfsops.h | 1 +
zfs/module/zfs/zpl_super.c | 11 ++++++++++-
3 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/zfs/META b/zfs/META
index 6837592..f34a9d6 100644
--- a/zfs/META
+++ b/zfs/META
@@ -2,7 +2,7 @@ Meta: 1
Name: zfs
Branch: 1.0
Version: 0.6.5.6
-Release: 0ubuntu24
+Release: 0ubuntu25
Release-Tags: relext
License: CDDL
Author: OpenZFS on Linux
diff --git a/zfs/include/sys/zfs_vfsops.h b/zfs/include/sys/zfs_vfsops.h
index efaefda..49eefba 100644
--- a/zfs/include/sys/zfs_vfsops.h
+++ b/zfs/include/sys/zfs_vfsops.h
@@ -32,6 +32,7 @@
#include <sys/zil.h>
#include <sys/sa.h>
#include <sys/rrwlock.h>
+#include <sys/dsl_dataset.h>
#include <sys/zfs_ioctl.h>
#ifdef __cplusplus
diff --git a/zfs/module/zfs/zpl_super.c b/zfs/module/zfs/zpl_super.c
index f75a0d8..fc467ae 100644
--- a/zfs/module/zfs/zpl_super.c
+++ b/zfs/module/zfs/zpl_super.c
@@ -467,8 +467,17 @@ zpl_mount_impl(struct file_system_type *fs_type, int flags, zfs_mntopts_t *zmo)
if (err)
return (ERR_PTR(-err));
+ /*
+ * The dsl pool lock must be released prior to calling sget().
+ * It is possible sget() may block on the lock in grab_super()
+ * while deactivate_super() holds that same lock and waits for
+ * a txg sync. If the dsl_pool lock is held over over sget()
+ * this can prevent the pool sync and cause a deadlock.
+ */
+ dsl_pool_rele(dmu_objset_pool(os), FTAG);
s = zpl_sget(fs_type, zpl_test_super, set_anon_super, flags, os);
- dmu_objset_rele(os, FTAG);
+ dsl_dataset_rele(dmu_objset_ds(os), FTAG);
+
if (IS_ERR(s))
return (ERR_CAST(s));
--
2.7.4
More information about the kernel-team
mailing list