librbd: add an interface to invalidate cached data

This is useful for qemu to guarantee live migration with caching is
safe, by invalidating the cache on the destination before starting it.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
(cherry picked from commit 5d340d26dd70192eb0e4f3f240e3433fb9a24154)

diff --git a/src/include/rbd/librbd.h b/src/include/rbd/librbd.h
index 5be82033390e81f335a01c962c765a1708bfb904..1e87af9d1944f997d34329fb5629baa8bba06457 100644 (file)
--- a/src/include/rbd/librbd.h
+++ b/src/include/rbd/librbd.h
@@ -39,6 +39,7 @@ extern "C" {
 
 #define LIBRBD_SUPPORTS_WATCH 0
 #define LIBRBD_SUPPORTS_AIO_FLUSH 1
+#define LIBRBD_SUPPORTS_INVALIDATE 1
 
 typedef void *rbd_snap_t;
 typedef void *rbd_image_t;
@@ -376,6 +377,14 @@ int rbd_flush(rbd_image_t image);
  */
 int rbd_aio_flush(rbd_image_t image, rbd_completion_t c);
 
+/**
+ * Drop any cached data for an image
+ *
+ * @param image the image to invalidate cached data for
+ * @returns 0 on success, negative error code on failure
+ */
+int rbd_invalidate_cache(rbd_image_t image);
+
 #ifdef __cplusplus
 }
 #endif

diff --git a/src/include/rbd/librbd.hpp b/src/include/rbd/librbd.hpp
index 697fc6ccc41e9ce1c3fe3bccbfd2b9847c613420..caf61a65f706918baa17040985141f6c05023de8 100644 (file)
--- a/src/include/rbd/librbd.hpp
+++ b/src/include/rbd/librbd.hpp
@@ -216,6 +216,14 @@ public:
    */
   int aio_flush(RBD::AioCompletion *c);
 
+  /**
+   * Drop any cached data for an image
+   *
+   * @param image the image to invalidate cached data for
+   * @returns 0 on success, negative error code on failure
+   */
+  int invalidate_cache();
+
 private:
   friend class RBD;
 

diff --git a/src/librbd/internal.cc b/src/librbd/internal.cc
index b13ff97cd9aeb095f14b0624deee18968ce49564..e56ef0897f48c3ddf5e7766f01f95a7592a3a588 100644 (file)
--- a/src/librbd/internal.cc
+++ b/src/librbd/internal.cc
@@ -2881,6 +2881,19 @@ reprotect_and_return_err:
     return r;
   }
 
+  int invalidate_cache(ImageCtx *ictx)
+  {
+    CephContext *cct = ictx->cct;
+    ldout(cct, 20) << "invalidate_cache " << ictx << dendl;
+
+    int r = ictx_check(ictx);
+    if (r < 0)
+      return r;
+
+    RWLock::WLocker l(ictx->md_lock);
+    return ictx->invalidate_cache();
+  }
+
   int aio_write(ImageCtx *ictx, uint64_t off, size_t len, const char *buf,
                AioCompletion *c)
   {

diff --git a/src/librbd/internal.h b/src/librbd/internal.h
index 43458886b430b3f423d4b22a4db890d1f5410c5a..6fb1af4617573566e9cec061125c85ca7fd34263 100644 (file)
--- a/src/librbd/internal.h
+++ b/src/librbd/internal.h
@@ -188,6 +188,7 @@ namespace librbd {
   int aio_flush(ImageCtx *ictx, AioCompletion *c);
   int flush(ImageCtx *ictx);
   int _flush(ImageCtx *ictx);
+  int invalidate_cache(ImageCtx *ictx);
 
   ssize_t handle_sparse_read(CephContext *cct,
                             ceph::bufferlist data_bl,

diff --git a/src/librbd/librbd.cc b/src/librbd/librbd.cc
index cad0c5eb17294400d9972736774090c9a8c260e3..658f24b85ca794a11e7c2d4a3f98044c2f95805d 100644 (file)
--- a/src/librbd/librbd.cc
+++ b/src/librbd/librbd.cc
@@ -514,6 +514,12 @@ namespace librbd {
     return librbd::aio_flush(ictx, (librbd::AioCompletion *)c->pc);
   }
 
+  int Image::invalidate_cache()
+  {
+    ImageCtx *ictx = (ImageCtx *)ctx;
+    return librbd::invalidate_cache(ictx);
+  }
+
 } // namespace librbd
 
 extern "C" void rbd_version(int *major, int *minor, int *extra)
@@ -1130,6 +1136,12 @@ extern "C" int rbd_aio_flush(rbd_image_t image, rbd_completion_t c)
   return librbd::aio_flush(ictx, (librbd::AioCompletion *)comp->pc);
 }
 
+extern "C" int rbd_invalidate_cache(rbd_image_t image)
+{
+  librbd::ImageCtx *ictx = (librbd::ImageCtx *)image;
+  return librbd::invalidate_cache(ictx);
+}
+
 extern "C" int rbd_aio_is_complete(rbd_completion_t c)
 {
   librbd::RBD::AioCompletion *comp = (librbd::RBD::AioCompletion *)c;

diff --git a/src/pybind/rbd.py b/src/pybind/rbd.py
index bf075769d8be07d54ae2f1ae624e0b9bb0ad1928..ab093ce30abd764ee4250764e6515d103d8a18c3 100644 (file)
--- a/src/pybind/rbd.py
+++ b/src/pybind/rbd.py
@@ -750,6 +750,14 @@ written." % (self.name, ret, length))
         if ret < 0:
             raise make_ex(ret, 'error flushing image')
 
+    def invalidate_cache(self):
+        """
+        Drop any cached data for the image.
+        """
+        ret = self.librbd.rbd_invalidate_cache(self.image)
+        if ret < 0:
+            raise make_ex(ret, 'error invalidating cache')
+
     def stripe_unit(self):
         """
         Returns the stripe unit used for the image.

diff --git a/src/test/pybind/test_rbd.py b/src/test/pybind/test_rbd.py
index f45391835183d764200d4dfef513015ebab4c711..11591820641d5c3e5ec4903760c8b28a43aeddde 100644 (file)
--- a/src/test/pybind/test_rbd.py
+++ b/src/test/pybind/test_rbd.py
@@ -229,6 +229,12 @@ class TestImage(object):
         self.image.close()
         remove_image()
 
+    def test_invalidate_cache(self):
+        self.image.write('abc', 0)
+        eq('abc', self.image.read(0, 3))
+        self.image.invalidate_cache()
+        eq('abc', self.image.read(0, 3))
+
     def test_stat(self):
         info = self.image.stat()
         check_stat(info, IMG_SIZE, IMG_ORDER)