From 3e1d0452edceebb903d23db53201013c940bf000 Mon Sep 17 00:00:00 2001 From: "Yan, Zheng" Date: Sat, 18 May 2019 20:39:55 +0800 Subject: ceph: avoid iput_final() while holding mutex or in dispatch thread iput_final() may wait for reahahead pages. The wait can cause deadlock. For example: Workqueue: ceph-msgr ceph_con_workfn [libceph] Call Trace: schedule+0x36/0x80 io_schedule+0x16/0x40 __lock_page+0x101/0x140 truncate_inode_pages_range+0x556/0x9f0 truncate_inode_pages_final+0x4d/0x60 evict+0x182/0x1a0 iput+0x1d2/0x220 iterate_session_caps+0x82/0x230 [ceph] dispatch+0x678/0xa80 [ceph] ceph_con_workfn+0x95b/0x1560 [libceph] process_one_work+0x14d/0x410 worker_thread+0x4b/0x460 kthread+0x105/0x140 ret_from_fork+0x22/0x40 Workqueue: ceph-msgr ceph_con_workfn [libceph] Call Trace: __schedule+0x3d6/0x8b0 schedule+0x36/0x80 schedule_preempt_disabled+0xe/0x10 mutex_lock+0x2f/0x40 ceph_check_caps+0x505/0xa80 [ceph] ceph_put_wrbuffer_cap_refs+0x1e5/0x2c0 [ceph] writepages_finish+0x2d3/0x410 [ceph] __complete_request+0x26/0x60 [libceph] handle_reply+0x6c8/0xa10 [libceph] dispatch+0x29a/0xbb0 [libceph] ceph_con_workfn+0x95b/0x1560 [libceph] process_one_work+0x14d/0x410 worker_thread+0x4b/0x460 kthread+0x105/0x140 ret_from_fork+0x22/0x40 In above example, truncate_inode_pages_range() waits for readahead pages while holding s_mutex. ceph_check_caps() waits for s_mutex and blocks OSD dispatch thread. Later OSD replies (for readahead) can't be handled. ceph_check_caps() also may lock snap_rwsem for read. So similar deadlock can happen if iput_final() is called while holding snap_rwsem. In general, it's not good to call iput_final() inside MDS/OSD dispatch threads or while holding any mutex. The fix is introducing ceph_async_iput(), which calls iput_final() in workqueue. Signed-off-by: "Yan, Zheng" Reviewed-by: Jeff Layton Signed-off-by: Ilya Dryomov --- fs/ceph/quota.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'fs/ceph/quota.c') diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c index c4522212872c..d629fc857450 100644 --- a/fs/ceph/quota.c +++ b/fs/ceph/quota.c @@ -74,7 +74,8 @@ void ceph_handle_quota(struct ceph_mds_client *mdsc, le64_to_cpu(h->max_files)); spin_unlock(&ci->i_ceph_lock); - iput(inode); + /* avoid calling iput_final() in dispatch thread */ + ceph_async_iput(inode); } static struct ceph_quotarealm_inode * @@ -235,7 +236,8 @@ restart: ci = ceph_inode(in); has_quota = __ceph_has_any_quota(ci); - iput(in); + /* avoid calling iput_final() while holding mdsc->snap_rwsem */ + ceph_async_iput(in); next = realm->parent; if (has_quota || !next) @@ -372,7 +374,8 @@ restart: pr_warn("Invalid quota check op (%d)\n", op); exceeded = true; /* Just break the loop */ } - iput(in); + /* avoid calling iput_final() while holding mdsc->snap_rwsem */ + ceph_async_iput(in); next = realm->parent; if (exceeded || !next) -- cgit v1.2.3-59-g8ed1b