open-behind: rewrite of internal logic

There was a critical flaw in the previous implementation of open-behind.

When an open is done in the background, it's necessary to take a
reference on the fd_t object because once we "fake" the open answer,
the fd could be destroyed. However as long as there's a reference,
the release function won't be called. So, if the application closes
the file descriptor without having actually opened it, there will
always remain at least 1 reference, causing a leak.

To avoid this problem, the previous implementation didn't take a
reference on the fd_t, so there were races where the fd could be
destroyed while it was still in use.

To fix this, I've implemented a new xlator cbk that gets called from
fuse when the application closes a file descriptor.

The whole logic of handling background opens have been simplified and
it's more efficient now. Only if the fop needs to be delayed until an
open completes, a stub is created. Otherwise no memory allocations are
needed.

Correctly handling the close request while the open is still pending
has added a bit of complexity, but overall normal operation is simpler.

Change-Id: I6376a5491368e0e1c283cc452849032636261592
Fixes: #1225
Signed-off-by: Xavi Hernandez <xhernandez@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/xlators/mount/fuse/src/fuse-bridge.c b/xlators/mount/fuse/src/fuse-bridge.c
index 108c44e4a32..8fac0745e21 100644
--- a/xlators/mount/fuse/src/fuse-bridge.c
+++ b/xlators/mount/fuse/src/fuse-bridge.c
@@ -3410,6 +3410,8 @@ fuse_release(xlator_t *this, fuse_in_header_t *finh, void *msg,
     gf_log("glusterfs-fuse", GF_LOG_TRACE,
            "finh->unique: %" PRIu64 ": RELEASE %p", finh->unique, state->fd);
 
+    fd_close(state->fd);
+
     fuse_fd_ctx_destroy(this, state->fd);
     fd_unref(fd);