On 2020/5/21 16:45, Yan, Zheng wrote:
On Thu, May 21, 2020 at 3:39 PM <xiubli@xxxxxxxxxx> wrote:
From: Xiubo Li <xiubli@xxxxxxxxxx>
In the ceph_check_caps() it may call the session lock/unlock stuff.
There have some deadlock cases, like:
handle_forward()
...
mutex_lock(&mdsc->mutex)
...
ceph_mdsc_put_request()
--> ceph_mdsc_release_request()
--> ceph_put_cap_request()
--> ceph_put_cap_refs()
--> ceph_check_caps()
...
mutex_unlock(&mdsc->mutex)
For this case, it's better to call ceph_mdsc_put_request() after
unlock mdsc->mutex
Hi Zheng Yan, Jeff
For this case there at least have 6 places, for some cases we can call
ceph_mdsc_put_request() after unlock mdsc->mutex very easily, but for
the others like:
cleanup_session_requests()
--> mutex_lock(&mdsc->mutex);
--> __unregister_request()
--> ceph_mdsc_put_request() ===> will call session lock/unlock pair
--> mutex_unlock(&mdsc->mutex);
There also has some more complicated cases, such as in handle_session(do
the mdsc->mutex lock/unlock pair) --> __wake_requests() -->
__do_request() --> __unregister_request() --> ceph_mdsc_put_request().
Maybe using the ceph_async_check_caps() is a better choice here, any idea ?
Thanks
BRs
Xiubo
And also there maybe has some double session lock cases, like:
send_mds_reconnect()
...
mutex_lock(&session->s_mutex);
...
--> replay_unsafe_requests()
--> ceph_mdsc_release_dir_caps()
--> ceph_put_cap_refs()
--> ceph_check_caps()
...
mutex_unlock(&session->s_mutex);
There is no point to check_caps() and send cap message while
reconnecting caps. So I think it's better to just skip calling
ceph_check_caps() for this case.
Regards
Yan, Zheng
URL: https://tracker.ceph.com/issues/45635
Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
---
fs/ceph/caps.c | 2 +-
fs/ceph/inode.c | 10 ++++++++++
fs/ceph/super.h | 12 ++++++++++++
3 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 27c2e60..08194c4 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -3073,7 +3073,7 @@ void ceph_put_cap_refs(struct ceph_inode_info *ci, int had)
last ? " last" : "", put ? " put" : "");
if (last)
- ceph_check_caps(ci, 0, NULL);
+ ceph_async_check_caps(ci);
else if (flushsnaps)
ceph_flush_snaps(ci, NULL);
if (wake)
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 357c937..84a61d4 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -35,6 +35,7 @@
static const struct inode_operations ceph_symlink_iops;
static void ceph_inode_work(struct work_struct *work);
+static void ceph_check_caps_work(struct work_struct *work);
/*
* find or create an inode, given the ceph ino number
@@ -518,6 +519,7 @@ struct inode *ceph_alloc_inode(struct super_block *sb)
INIT_LIST_HEAD(&ci->i_snap_flush_item);
INIT_WORK(&ci->i_work, ceph_inode_work);
+ INIT_WORK(&ci->check_caps_work, ceph_check_caps_work);
ci->i_work_mask = 0;
memset(&ci->i_btime, '\0', sizeof(ci->i_btime));
@@ -2012,6 +2014,14 @@ static void ceph_inode_work(struct work_struct *work)
iput(inode);
}
+static void ceph_check_caps_work(struct work_struct *work)
+{
+ struct ceph_inode_info *ci = container_of(work, struct ceph_inode_info,
+ check_caps_work);
+
+ ceph_check_caps(ci, 0, NULL);
+}
+
/*
* symlinks
*/
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 226f19c..96d0e41 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -421,6 +421,8 @@ struct ceph_inode_info {
struct timespec64 i_btime;
struct timespec64 i_snap_btime;
+ struct work_struct check_caps_work;
+
struct work_struct i_work;
unsigned long i_work_mask;
@@ -1102,6 +1104,16 @@ extern void ceph_flush_snaps(struct ceph_inode_info *ci,
extern bool __ceph_should_report_size(struct ceph_inode_info *ci);
extern void ceph_check_caps(struct ceph_inode_info *ci, int flags,
struct ceph_mds_session *session);
+static void inline
+ceph_async_check_caps(struct ceph_inode_info *ci)
+{
+ struct inode *inode = &ci->vfs_inode;
+
+ /* It's okay if queue_work fails */
+ queue_work(ceph_inode_to_client(inode)->inode_wq,
+ &ceph_inode(inode)->check_caps_work);
+}
+
extern void ceph_check_delayed_caps(struct ceph_mds_client *mdsc);
extern void ceph_flush_dirty_caps(struct ceph_mds_client *mdsc);
extern int ceph_drop_caps_for_unlink(struct inode *inode);
--
1.8.3.1
