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libceph: defer __complete_request() to a workqueue

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In the common case, req->r_callback is called by handle_reply() on the
ceph-msgr worker thread without any locks.  If handle_reply() fails, it
is called with both osd->lock and osdc->lock.  In the map check case,
it is called with just osdc->lock but held for write.  Finally, if the
request is aborted because of -ENOSPC or by ceph_osdc_abort_requests(),
it is called directly on the submitter's thread, again with both locks.

req->r_callback on the submitter's thread is relatively new (introduced
in 4.12) and ripe for deadlocks -- e.g. writeback worker thread waiting
on itself:

  inode_wait_for_writeback+0x26/0x40
  evict+0xb5/0x1a0
  iput+0x1d2/0x220
  ceph_put_wrbuffer_cap_refs+0xe0/0x2c0 [ceph]
  writepages_finish+0x2d3/0x410 [ceph]
  __complete_request+0x26/0x60 [libceph]
  complete_request+0x2e/0x70 [libceph]
  __submit_request+0x256/0x330 [libceph]
  submit_request+0x2b/0x30 [libceph]
  ceph_osdc_start_request+0x25/0x40 [libceph]
  ceph_writepages_start+0xdfe/0x1320 [ceph]
  do_writepages+0x1f/0x70
  __writeback_single_inode+0x45/0x330
  writeback_sb_inodes+0x26a/0x600
  __writeback_inodes_wb+0x92/0xc0
  wb_writeback+0x274/0x330
  wb_workfn+0x2d5/0x3b0

Defer __complete_request() to a workqueue in all failure cases so it's
never on the same thread as ceph_osdc_start_request() and always called
with no locks held.

Link: http://tracker.ceph.com/issues/23978
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
This commit is contained in:
Ilya Dryomov 2018-05-21 16:00:29 +02:00
parent 26df726bcd
commit 88bc1922c2
2 changed files with 20 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

2
include/linux/ceph/osd_client.h
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@ -170,6 +170,7 @@ struct ceph_osd_request {
u64 r_tid; /* unique for this client */
struct rb_node r_node;
struct rb_node r_mc_node; /* map check */
struct work_struct r_complete_work;
struct ceph_osd *r_osd;
struct ceph_osd_request_target r_t;
@ -360,6 +361,7 @@ struct ceph_osd_client {
struct ceph_msgpool msgpool_op_reply;
struct workqueue_struct *notify_wq;
struct workqueue_struct *completion_wq;
};
static inline bool ceph_osdmap_flag(struct ceph_osd_client *osdc, int flag)