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authorYan, Zheng <zyan@redhat.com>2019-05-18 20:39:55 +0800
committerIlya Dryomov <idryomov@gmail.com>2019-06-05 20:34:39 +0200
commit3e1d0452edceebb903d23db53201013c940bf000 (patch)
tree1a6065a9b2fcd52395ae35778cf9de0ad43d0b30 /fs/efs
parent1cf89a8dee5e6e9d4fcb81b571a54d40068dfbb7 (diff)
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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" <zyan@redhat.com> Reviewed-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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