cfuse: properly invalidate page cache data via callback

The Client has a cache, but it is actually usually duplicating
what the kernel has in the page cache.  Use the Client callback to do a
libfuse upcall to invalidate the kernel page cache when appropriate.

Usually people didn't notice this because we were invalidating the page
cache on every file open. Stop doing that.

This gives us:
 - consistent multi-client semantics for open files
 - fewer read calls because the kernel can (re)use the page cache more
   effectively.

We are still double-caching.  We probably want to be aggressive about not
caching any clean file data in Client from cfuse since the page cache does
a better job than we do.

Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/src/client/fuse_ll.cc b/src/client/fuse_ll.cc
index 1cb79c864f9caa6c342676d7acd805e846ed02c6..9a5f85125fedb32ee25521613683af96bb531869 100644 (file)
--- a/src/client/fuse_ll.cc
+++ b/src/client/fuse_ll.cc
@@ -321,6 +321,7 @@ static void ceph_ll_open(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *
   int r = client->ll_open(fino_vino(ino), fi->flags, &fh, ctx->uid, ctx->gid);
   if (r == 0) {
     fi->fh = (long)fh;
+    fi->keep_cache = 1;
     fuse_reply_open(req, fi);
   } else {
     fuse_reply_err(req, -r);
@@ -460,6 +461,14 @@ static void ceph_ll_statfs(fuse_req_t req, fuse_ino_t ino)
     fuse_reply_err(req, -r);
 }
 
+
+static void invalidate_cb(void *handle, vinodeno_t vino, int64_t off, int64_t len)
+{
+  struct fuse_chan *ch = (struct fuse_chan *)handle;
+  fuse_ino_t fino = make_fake_ino(vino.ino, vino.snapid);
+  fuse_lowlevel_notify_inval_inode(ch, fino, off, len);
+}
+
 int fd_on_success = 0;
 
 static void do_init(void *foo, fuse_conn_info *bar)
@@ -550,7 +559,8 @@ int ceph_fuse_ll_main(Client *c, int argc, const char *argv[], int fd)
 
   //newargv[newargc++] = "-d";
 
-  for (int argctr = 1; argctr < argc; argctr++) newargv[newargc++] = argv[argctr];
+  for (int argctr = 1; argctr < argc; argctr++)
+    newargv[newargc++] = argv[argctr];
 
   // go go gadget fuse
   struct fuse_args args = FUSE_ARGS_INIT(newargc, (char**)newargv);
@@ -588,7 +598,13 @@ int ceph_fuse_ll_main(Client *c, int argc, const char *argv[], int fd)
   }
 
   fuse_session_add_chan(se, ch);
+
+  client->ll_register_ino_invalidate_cb(invalidate_cb, ch);
+
   ret = fuse_session_loop(se);
+
+  client->ll_register_ino_invalidate_cb(NULL, NULL);
+
   fuse_remove_signal_handlers(se);
   fuse_session_remove_chan(ch);