diff options
| author | Yan, Zheng <zyan@redhat.com> | 2019-05-18 15:39:55 +0300 |
|---|---|---|
| committer | Ilya Dryomov <idryomov@gmail.com> | 2019-06-05 21:34:39 +0300 |
| commit | 3e1d0452edceebb903d23db53201013c940bf000 (patch) | |
| tree | 1a6065a9b2fcd52395ae35778cf9de0ad43d0b30 /fs/ceph/snap.c | |
| parent | 1cf89a8dee5e6e9d4fcb81b571a54d40068dfbb7 (diff) | |
| download | linux-3e1d0452edceebb903d23db53201013c940bf000.tar.xz | |
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/snap.c')
| -rw-r--r-- | fs/ceph/snap.c | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c index b26e12cd8ec3..72c6c022f02b 100644 --- a/fs/ceph/snap.c +++ b/fs/ceph/snap.c @@ -648,13 +648,15 @@ static void queue_realm_cap_snaps(struct ceph_snap_realm *realm) if (!inode) continue; spin_unlock(&realm->inodes_with_caps_lock); - iput(lastinode); + /* avoid calling iput_final() while holding + * mdsc->snap_rwsem or in mds dispatch threads */ + ceph_async_iput(lastinode); lastinode = inode; ceph_queue_cap_snap(ci); spin_lock(&realm->inodes_with_caps_lock); } spin_unlock(&realm->inodes_with_caps_lock); - iput(lastinode); + ceph_async_iput(lastinode); dout("queue_realm_cap_snaps %p %llx done\n", realm, realm->ino); } @@ -806,7 +808,9 @@ static void flush_snaps(struct ceph_mds_client *mdsc) ihold(inode); spin_unlock(&mdsc->snap_flush_lock); ceph_flush_snaps(ci, &session); - iput(inode); + /* avoid calling iput_final() while holding + * session->s_mutex or in mds dispatch threads */ + ceph_async_iput(inode); spin_lock(&mdsc->snap_flush_lock); } spin_unlock(&mdsc->snap_flush_lock); @@ -950,12 +954,14 @@ void ceph_handle_snap(struct ceph_mds_client *mdsc, ceph_get_snap_realm(mdsc, realm); ceph_put_snap_realm(mdsc, oldrealm); - iput(inode); + /* avoid calling iput_final() while holding + * mdsc->snap_rwsem or mds in dispatch threads */ + ceph_async_iput(inode); continue; skip_inode: spin_unlock(&ci->i_ceph_lock); - iput(inode); + ceph_async_iput(inode); } /* we may have taken some of the old realm's children. */ |