librbd: only clear the needs_refresh flag on successful updates.

To support this, add a refresh_seq counter which is incremented every
time we get a notify. This way we can handle the concern from
7add136f907876a20aa2a68297c66b8259afd9a7, in which we get a notify
in the middle of doing a refresh.

Signed-off-by: Greg Farnum <greg@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/src/librbd.cc b/src/librbd.cc
index 73fd6cbd639c0bbe35ec8461b211c88149f1ca6a..deebd6cde9dcc45a9231a4846d5396e2b41818fe 100644 (file)
--- a/src/librbd.cc
+++ b/src/librbd.cc
@@ -160,6 +160,7 @@ namespace librbd {
     IoCtx data_ctx, md_ctx;
     WatchCtx *wctx;
     bool needs_refresh;
+    int refresh_seq;
     Mutex refresh_lock;
     Mutex lock; // protects access to snapshot and header information
     Mutex cache_lock; // used as client_lock for the ObjectCacher
@@ -182,6 +183,7 @@ namespace librbd {
        snap_exists(true),
        name(imgname),
        needs_refresh(true),
+       refresh_seq(0),
        refresh_lock("librbd::ImageCtx::refresh_lock"),
        lock("librbd::ImageCtx::lock"),
        cache_lock("librbd::ImageCtx::cache_lock"),
@@ -652,6 +654,7 @@ void WatchCtx::notify(uint8_t opcode, uint64_t ver, bufferlist& bl)
   if (valid) {
     Mutex::Locker lictx(ictx->refresh_lock);
     ictx->needs_refresh = true;
+    ++ictx->refresh_seq;
     ictx->perfcounter->inc(l_librbd_notify);
   }
 }
@@ -835,6 +838,7 @@ int notify_change(IoCtx& io_ctx, const string& oid, uint64_t *pver, ImageCtx *ic
     assert(ictx->lock.is_locked());
     ictx->refresh_lock.Lock();
     ictx->needs_refresh = true;
+    ++ictx->refresh_seq;
     ictx->refresh_lock.Unlock();
   }
 
@@ -1345,7 +1349,7 @@ int ictx_refresh(ImageCtx *ictx)
   ldout(cct, 20) << "ictx_refresh " << ictx << dendl;
 
   ictx->refresh_lock.Lock();
-  ictx->needs_refresh = false;
+  int refresh_seq = ictx->refresh_seq;
   ictx->refresh_lock.Unlock();
 
   int r;
@@ -1421,9 +1425,6 @@ int ictx_refresh(ImageCtx *ictx)
 
   if (!ictx->snapc.is_valid()) {
     lderr(cct) << "image snap context is invalid!" << dendl;
-    ictx->refresh_lock.Lock();
-    ictx->needs_refresh = true;
-    ictx->refresh_lock.Unlock();
     return -EIO;
   }
 
@@ -1438,6 +1439,12 @@ int ictx_refresh(ImageCtx *ictx)
 
   ictx->data_ctx.selfmanaged_snap_set_write_ctx(ictx->snapc.seq, ictx->snaps);
 
+  ictx->refresh_lock.Lock();
+  if (refresh_seq == ictx->refresh_seq) {
+    ictx->needs_refresh = false;
+  }
+  ictx->refresh_lock.Unlock();
+
   return 0;
 }