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authorAlex Elder <elder@inktank.com>2013-04-15 11:20:42 -0500
committerSage Weil <sage@inktank.com>2013-05-01 21:18:52 -0700
commit26be88087ae8a04a5b576aa2f490597b649fc132 (patch)
parent7d7d51ce14fde491a6d0677d9bded9b3bd0d21d9 (diff)
libceph: change how "safe" callback is used
An osd request currently has two callbacks. They inform the initiator of the request when we've received confirmation for the target osd that a request was received, and when the osd indicates all changes described by the request are durable. The only time the second callback is used is in the ceph file system for a synchronous write. There's a race that makes some handling of this case unsafe. This patch addresses this problem. The error handling for this callback is also kind of gross, and this patch changes that as well. In ceph_sync_write(), if a safe callback is requested we want to add the request on the ceph inode's unsafe items list. Because items on this list must have their tid set (by ceph_osd_start_request()), the request added *after* the call to that function returns. The problem with this is that there's a race between starting the request and adding it to the unsafe items list; the request may already be complete before ceph_sync_write() even begins to put it on the list. To address this, we change the way the "safe" callback is used. Rather than just calling it when the request is "safe", we use it to notify the initiator the bounds (start and end) of the period during which the request is *unsafe*. So the initiator gets notified just before the request gets sent to the osd (when it is "unsafe"), and again when it's known the results are durable (it's no longer unsafe). The first call will get made in __send_request(), just before the request message gets sent to the messenger for the first time. That function is only called by __send_queued(), which is always called with the osd client's request mutex held. We then have this callback function insert the request on the ceph inode's unsafe list when we're told the request is unsafe. This will avoid the race because this call will be made under protection of the osd client's request mutex. It also nicely groups the setup and cleanup of the state associated with managing unsafe requests. The name of the "safe" callback field is changed to "unsafe" to better reflect its new purpose. It has a Boolean "unsafe" parameter to indicate whether the request is becoming unsafe or is now safe. Because the "msg" parameter wasn't used, we drop that. This resolves the original problem reportedin: http://tracker.ceph.com/issues/4706 Reported-by: Yan, Zheng <zheng.z.yan@intel.com> Signed-off-by: Alex Elder <elder@inktank.com> Reviewed-by: Yan, Zheng <zheng.z.yan@intel.com> Reviewed-by: Sage Weil <sage@inktank.com>
3 files changed, 40 insertions, 28 deletions
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index ae23e31a8f38..a65acf355384 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -446,19 +446,35 @@ done:
- * Write commit callback, called if we requested both an ACK and
- * ONDISK commit reply from the OSD.
+ * Write commit request unsafe callback, called to tell us when a
+ * request is unsafe (that is, in flight--has been handed to the
+ * messenger to send to its target osd). It is called again when
+ * we've received a response message indicating the request is
+ * "safe" (its CEPH_OSD_FLAG_ONDISK flag is set), or when a request
+ * is completed early (and unsuccessfully) due to a timeout or
+ * interrupt.
+ *
+ * This is used if we requested both an ACK and ONDISK commit reply
+ * from the OSD.
-static void sync_write_commit(struct ceph_osd_request *req,
- struct ceph_msg *msg)
+static void ceph_sync_write_unsafe(struct ceph_osd_request *req, bool unsafe)
struct ceph_inode_info *ci = ceph_inode(req->r_inode);
- dout("sync_write_commit %p tid %llu\n", req, req->r_tid);
- spin_lock(&ci->i_unsafe_lock);
- list_del_init(&req->r_unsafe_item);
- spin_unlock(&ci->i_unsafe_lock);
- ceph_put_cap_refs(ci, CEPH_CAP_FILE_WR);
+ dout("%s %p tid %llu %ssafe\n", __func__, req, req->r_tid,
+ unsafe ? "un" : "");
+ if (unsafe) {
+ ceph_get_cap_refs(ci, CEPH_CAP_FILE_WR);
+ spin_lock(&ci->i_unsafe_lock);
+ list_add_tail(&req->r_unsafe_item,
+ &ci->i_unsafe_writes);
+ spin_unlock(&ci->i_unsafe_lock);
+ } else {
+ spin_lock(&ci->i_unsafe_lock);
+ list_del_init(&req->r_unsafe_item);
+ spin_unlock(&ci->i_unsafe_lock);
+ ceph_put_cap_refs(ci, CEPH_CAP_FILE_WR);
+ }
@@ -570,7 +586,8 @@ more:
if ((file->f_flags & O_SYNC) == 0) {
/* get a second commit callback */
- req->r_safe_callback = sync_write_commit;
+ req->r_unsafe_callback = ceph_sync_write_unsafe;
+ req->r_inode = inode;
own_pages = true;
@@ -581,21 +598,8 @@ more:
ceph_osdc_build_request(req, pos, snapc, vino.snap, &mtime);
ret = ceph_osdc_start_request(&fsc->client->osdc, req, false);
- if (!ret) {
- if (req->r_safe_callback) {
- /*
- * Add to inode unsafe list only after we
- * start_request so that a tid has been assigned.
- */
- spin_lock(&ci->i_unsafe_lock);
- list_add_tail(&req->r_unsafe_item,
- &ci->i_unsafe_writes);
- spin_unlock(&ci->i_unsafe_lock);
- ceph_get_cap_refs(ci, CEPH_CAP_FILE_WR);
- }
+ if (!ret)
ret = ceph_osdc_wait_request(&fsc->client->osdc, req);
- }
if (file->f_flags & O_DIRECT)
ceph_put_page_vector(pages, num_pages, false);
diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
index 2a68a7465c18..0d3358ef5285 100644
--- a/include/linux/ceph/osd_client.h
+++ b/include/linux/ceph/osd_client.h
@@ -29,6 +29,7 @@ struct ceph_authorizer;
typedef void (*ceph_osdc_callback_t)(struct ceph_osd_request *,
struct ceph_msg *);
+typedef void (*ceph_osdc_unsafe_callback_t)(struct ceph_osd_request *, bool);
/* a given osd we're communicating with */
struct ceph_osd {
@@ -149,7 +150,8 @@ struct ceph_osd_request {
struct kref r_kref;
bool r_mempool;
struct completion r_completion, r_safe_completion;
- ceph_osdc_callback_t r_callback, r_safe_callback;
+ ceph_osdc_callback_t r_callback;
+ ceph_osdc_unsafe_callback_t r_unsafe_callback;
struct ceph_eversion r_reassert_version;
struct list_head r_unsafe_item;
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 939be67199ca..0c5bf2fb5075 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -1314,8 +1314,14 @@ static void __send_request(struct ceph_osd_client *osdc,
list_move_tail(&req->r_req_lru_item, &osdc->req_lru);
ceph_msg_get(req->r_request); /* send consumes a ref */
- ceph_con_send(&req->r_osd->o_con, req->r_request);
+ /* Mark the request unsafe if this is the first timet's being sent. */
+ if (!req->r_sent && req->r_unsafe_callback)
+ req->r_unsafe_callback(req, true);
req->r_sent = req->r_osd->o_incarnation;
+ ceph_con_send(&req->r_osd->o_con, req->r_request);
@@ -1403,8 +1409,8 @@ static void handle_osds_timeout(struct work_struct *work)
static void complete_request(struct ceph_osd_request *req)
- if (req->r_safe_callback)
- req->r_safe_callback(req, NULL);
+ if (req->r_unsafe_callback)
+ req->r_unsafe_callback(req, false);
complete_all(&req->r_safe_completion); /* fsync waiter */

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