ceph: fix rdcache_gen usage and invalidate

We used to use rdcache_gen to indicate whether we "might" have cached
pages.  Now we just look at the mapping to determine that.  However, some
old behavior remains from that transition.

First, rdcache_gen == 0 no longer means we have no pages.  That can happen
at any time (presumably when we carry FILE_CACHE).  We should not reset it
to zero, and we should not check that it is zero.

That means that the only purpose for rdcache_revoking is to resolve races
between new issues of FILE_CACHE and an async invalidate.  If they are
equal, we should invalidate.  On success, we decrement rdcache_revoking,
so that it is no longer equal to rdcache_gen.  Similarly, if we success
in doing a sync invalidate, set revoking = gen - 1.  (This is a small
optimization to avoid doing unnecessary invalidate work and does not
affect correctness.)

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

1 files changed, 1 insertions, 3 deletions

diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 1886294..7f01728 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -293,9 +293,7 @@ struct ceph_inode_info {
 	int i_rd_ref, i_rdcache_ref, i_wr_ref;
 	int i_wrbuffer_ref, i_wrbuffer_ref_head;
 	u32 i_shared_gen;       /* increment each time we get FILE_SHARED */
-	u32 i_rdcache_gen;      /* we increment this each time we get
-				   FILE_CACHE.  If it's non-zero, we
-				   _may_ have cached pages. */
+	u32 i_rdcache_gen;      /* incremented each time we get FILE_CACHE. */
 	u32 i_rdcache_revoking; /* RDCACHE gen to async invalidate, if any */
 
 	struct list_head i_unsafe_writes; /* uncommitted sync writes */