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| author |   Yan, Zheng <zyan@redhat.com> | 2019-05-18 20:39:55 +0800 |
|---|---|---|
| committer |   Ilya Dryomov <idryomov@gmail.com> | 2019-06-05 20:34:39 +0200 |
| commit | 3e1d0452edceebb903d23db53201013c940bf000 (patch) | |
| tree | 1a6065a9b2fcd52395ae35778cf9de0ad43d0b30 /fs/ceph/quota.c | |
| parent | ceph: single workqueue for inode related works (diff) | |
| download | wireguard-linux-3e1d0452edceebb903d23db53201013c940bf000.tar.xz wireguard-linux-3e1d0452edceebb903d23db53201013c940bf000.zip | |
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>
Diffstat (limited to 'fs/ceph/quota.c')
| -rw-r--r-- | fs/ceph/quota.c | 9 |
1 files changed, 6 insertions, 3 deletions
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) |