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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>
This commit is contained in:
Yan, Zheng 2019-05-18 20:39:55 +08:00 committed by Ilya Dryomov
parent 1cf89a8dee
commit 3e1d0452ed
6 changed files with 71 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
fs/ceph/caps.c
View File

@ -2992,8 +2992,10 @@ void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr,
}
if (complete_capsnap)
wake_up_all(&ci->i_cap_wq);
while (put-- > 0)
iput(inode);
while (put-- > 0) {
/* avoid calling iput_final() in osd dispatch threads */
ceph_async_iput(inode);
}
}
/*
@ -3964,8 +3966,9 @@ void ceph_handle_caps(struct ceph_mds_session *session,
done:
mutex_unlock(&session->s_mutex);
done_unlocked:
iput(inode);
ceph_put_string(extra_info.pool_ns);
/* avoid calling iput_final() in mds dispatch threads */
ceph_async_iput(inode);
return;
flush_cap_releases:
@ -4011,7 +4014,8 @@ void ceph_check_delayed_caps(struct ceph_mds_client *mdsc)
if (inode) {
dout("check_delayed_caps on %p\n", inode);
ceph_check_caps(ci, flags, NULL);
iput(inode);
/* avoid calling iput_final() in tick thread */
ceph_async_iput(inode);
}
}
spin_unlock(&mdsc->cap_delay_lock);

31
fs/ceph/inode.c
View File

@ -1476,7 +1476,8 @@ static int readdir_prepopulate_inodes_only(struct ceph_mds_request *req,
pr_err("fill_inode badness on %p got %d\n", in, rc);
err = rc;
}
iput(in);
/* avoid calling iput_final() in mds dispatch threads */
ceph_async_iput(in);
}
return err;
@ -1674,8 +1675,11 @@ retry_lookup:
&req->r_caps_reservation);
if (ret < 0) {
pr_err("fill_inode badness on %p\n", in);
if (d_really_is_negative(dn))
iput(in);
if (d_really_is_negative(dn)) {
/* avoid calling iput_final() in mds
* dispatch threads */
ceph_async_iput(in);
}
d_drop(dn);
err = ret;
goto next_item;
@ -1685,7 +1689,7 @@ retry_lookup:
if (ceph_security_xattr_deadlock(in)) {
dout(" skip splicing dn %p to inode %p"
" (security xattr deadlock)\n", dn, in);
iput(in);
ceph_async_iput(in);
skipped++;
goto next_item;
}
@ -1736,6 +1740,25 @@ bool ceph_inode_set_size(struct inode *inode, loff_t size)
return ret;
}
/*
* Put reference to inode, but avoid calling iput_final() in current thread.
* iput_final() may wait for reahahead pages. The wait can cause deadlock in
* some contexts.
*/
void ceph_async_iput(struct inode *inode)
{
if (!inode)
return;
for (;;) {
if (atomic_add_unless(&inode->i_count, -1, 1))
break;
if (queue_work(ceph_inode_to_client(inode)->inode_wq,
&ceph_inode(inode)->i_work))
break;
/* queue work failed, i_count must be at least 2 */
}
}
/*
* Write back inode data in a worker thread. (This can't be done
* in the message handler context.)

28
fs/ceph/mds_client.c
View File

@ -690,11 +690,12 @@ void ceph_mdsc_release_request(struct kref *kref)
ceph_msg_put(req->r_reply);
if (req->r_inode) {
ceph_put_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
iput(req->r_inode);
/* avoid calling iput_final() in mds dispatch threads */
ceph_async_iput(req->r_inode);
}
if (req->r_parent)
ceph_put_cap_refs(ceph_inode(req->r_parent), CEPH_CAP_PIN);
iput(req->r_target_inode);
ceph_async_iput(req->r_target_inode);
if (req->r_dentry)
dput(req->r_dentry);
if (req->r_old_dentry)
@ -708,7 +709,7 @@ void ceph_mdsc_release_request(struct kref *kref)
*/
ceph_put_cap_refs(ceph_inode(req->r_old_dentry_dir),
CEPH_CAP_PIN);
iput(req->r_old_dentry_dir);
ceph_async_iput(req->r_old_dentry_dir);
}
kfree(req->r_path1);
kfree(req->r_path2);
@ -818,7 +819,8 @@ static void __unregister_request(struct ceph_mds_client *mdsc,
}
if (req->r_unsafe_dir) {
iput(req->r_unsafe_dir);
/* avoid calling iput_final() in mds dispatch threads */
ceph_async_iput(req->r_unsafe_dir);
req->r_unsafe_dir = NULL;
}
@ -983,7 +985,7 @@ static int __choose_mds(struct ceph_mds_client *mdsc,
cap = rb_entry(rb_first(&ci->i_caps), struct ceph_cap, ci_node);
if (!cap) {
spin_unlock(&ci->i_ceph_lock);
iput(inode);
ceph_async_iput(inode);
goto random;
}
mds = cap->session->s_mds;
@ -992,7 +994,9 @@ static int __choose_mds(struct ceph_mds_client *mdsc,
cap == ci->i_auth_cap ? "auth " : "", cap);
spin_unlock(&ci->i_ceph_lock);
out:
iput(inode);
/* avoid calling iput_final() while holding mdsc->mutex or
* in mds dispatch threads */
ceph_async_iput(inode);
return mds;
random:
@ -1302,7 +1306,9 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session,
spin_unlock(&session->s_cap_lock);
if (last_inode) {
iput(last_inode);
/* avoid calling iput_final() while holding
* s_mutex or in mds dispatch threads */
ceph_async_iput(last_inode);
last_inode = NULL;
}
if (old_cap) {
@ -1335,7 +1341,7 @@ out:
session->s_cap_iterator = NULL;
spin_unlock(&session->s_cap_lock);
iput(last_inode);
ceph_async_iput(last_inode);
if (old_cap)
ceph_put_cap(session->s_mdsc, old_cap);
@ -1471,7 +1477,8 @@ static void remove_session_caps(struct ceph_mds_session *session)
spin_unlock(&session->s_cap_lock);
inode = ceph_find_inode(sb, vino);
iput(inode);
/* avoid calling iput_final() while holding s_mutex */
ceph_async_iput(inode);
spin_lock(&session->s_cap_lock);
}
@ -3912,8 +3919,9 @@ release:
ceph_con_send(&session->s_con, msg);
out:
iput(inode);
mutex_unlock(&session->s_mutex);
/* avoid calling iput_final() in mds dispatch threads */
ceph_async_iput(inode);
return;
bad:

9
fs/ceph/quota.c
View File

@ -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)

16
fs/ceph/snap.c
View File

@ -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. */

2
fs/ceph/super.h
View File

@ -899,9 +899,9 @@ extern int ceph_inode_holds_cap(struct inode *inode, int mask);
extern bool ceph_inode_set_size(struct inode *inode, loff_t size);
extern void __ceph_do_pending_vmtruncate(struct inode *inode);
extern void ceph_queue_vmtruncate(struct inode *inode);
extern void ceph_queue_invalidate(struct inode *inode);
extern void ceph_queue_writeback(struct inode *inode);
extern void ceph_async_iput(struct inode *inode);
extern int __ceph_do_getattr(struct inode *inode, struct page *locked_page,
int mask, bool force);