projects / zfsonlinux.git / blame
| Commit | Line | Data |
|---|---|---|
| 76a4c29a SI |
1 | From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 |
| 2 | From: Rohan Puri <rohan.puri15@gmail.com> | |
| 3 | Date: Sat, 28 Jul 2018 18:32:12 +0530 | |
| 4 | Subject: [PATCH] Fix deadlock between zfs umount & snapentry_expire | |
| 5 | ||
| 6 | zfs umount -> zfsctl_destroy() takes the zfs_snapshot_lock as a | |
| 7 | writer and calls zfsctl_snapshot_unmount_cancel(), which waits | |
| 8 | for snapentry_expire() if present (when snap is automounted). | |
| 9 | This snapentry_expire() itself then waits for zfs_snapshot_lock | |
| 10 | as a reader, resulting in a deadlock. | |
| 11 | ||
| 12 | The fix is to only hold the zfs_snapshot_lock over the tree | |
| 13 | lookup and removal. After a successful lookup the lock can | |
| 14 | be dropped and zfs_snapentry_t will remain valid until the | |
| 15 | reference taken by the lookup is released. | |
| 16 | ||
| 17 | Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> | |
| 18 | Signed-off-by: Rohan Puri <rohan.puri15@gmail.com> | |
| 19 | Closes #7751 | |
| 20 | Closes #7752 | |
| 21 | ||
| 22 | (Cherry-picked from fd7265c646f40e364396af5014bbb83e809e124a) | |
| f587002c SI |
23 | Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com> |
| 24 | ||
| 76a4c29a SI |
25 | Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com> |
| 26 | --- | |
| 27 | module/zfs/zfs_ctldir.c | 11 +++++------ | |
| 28 | 1 file changed, 5 insertions(+), 6 deletions(-) | |
| 29 | ||
| 30 | diff --git a/module/zfs/zfs_ctldir.c b/module/zfs/zfs_ctldir.c | |
| f587002c | 31 | index 98897fe6..0ab5b4f0 100644 |
| 76a4c29a SI |
32 | --- a/module/zfs/zfs_ctldir.c |
| 33 | +++ b/module/zfs/zfs_ctldir.c | |
| 34 | @@ -358,8 +358,6 @@ snapentry_expire(void *data) | |
| 35 | static void | |
| 36 | zfsctl_snapshot_unmount_cancel(zfs_snapentry_t *se) | |
| 37 | { | |
| 38 | - ASSERT(RW_LOCK_HELD(&zfs_snapshot_lock)); | |
| 39 | - | |
| 40 | if (taskq_cancel_id(system_delay_taskq, se->se_taskqid) == 0) { | |
| 41 | se->se_taskqid = TASKQID_INVALID; | |
| 42 | zfsctl_snapshot_rele(se); | |
| 43 | @@ -570,13 +568,14 @@ zfsctl_destroy(zfsvfs_t *zfsvfs) | |
| 44 | uint64_t objsetid = dmu_objset_id(zfsvfs->z_os); | |
| 45 | ||
| 46 | rw_enter(&zfs_snapshot_lock, RW_WRITER); | |
| 47 | - if ((se = zfsctl_snapshot_find_by_objsetid(spa, objsetid)) | |
| 48 | - != NULL) { | |
| 49 | - zfsctl_snapshot_unmount_cancel(se); | |
| 50 | + se = zfsctl_snapshot_find_by_objsetid(spa, objsetid); | |
| 51 | + if (se != NULL) | |
| 52 | zfsctl_snapshot_remove(se); | |
| 53 | + rw_exit(&zfs_snapshot_lock); | |
| 54 | + if (se != NULL) { | |
| 55 | + zfsctl_snapshot_unmount_cancel(se); | |
| 56 | zfsctl_snapshot_rele(se); | |
| 57 | } | |
| 58 | - rw_exit(&zfs_snapshot_lock); | |
| 59 | } else if (zfsvfs->z_ctldir) { | |
| 60 | iput(zfsvfs->z_ctldir); | |
| 61 | zfsvfs->z_ctldir = NULL; |