ceph: fix check for invalidate_mapping_pages success

We need to know whether there was any page left behind, and not the
return value (the total number of pages invalidated).  Look at the mapping
to see if we were successful or not.

Move it all into a helper to simplify the two callers.

Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/caps.c

@@ -1361,6 +1361,41 @@ static int __mark_caps_flushing(struct inode *inode,
 	return flushing;
 }
 
+/*
+ * try to invalidate mapping pages without blocking.
+ */
+static int mapping_is_empty(struct address_space *mapping)
+{
+	struct page *page = find_get_page(mapping, 0);
+
+	if (!page)
+		return 1;
+
+	put_page(page);
+	return 0;
+}
+
+static int try_nonblocking_invalidate(struct inode *inode)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	u32 invalidating_gen = ci->i_rdcache_gen;
+
+	spin_unlock(&inode->i_lock);
+	invalidate_mapping_pages(&inode->i_data, 0, -1);
+	spin_lock(&inode->i_lock);
+
+	if (mapping_is_empty(&inode->i_data) &&
+	    invalidating_gen == ci->i_rdcache_gen) {
+		/* success. */
+		dout("try_nonblocking_invalidate %p success\n", inode);
+		ci->i_rdcache_gen = 0;
+		ci->i_rdcache_revoking = 0;
+		return 0;
+	}
+	dout("try_nonblocking_invalidate %p failed\n", inode);
+	return -1;
+}
+
 /*
  * Swiss army knife function to examine currently used and wanted
  * versus held caps.  Release, flush, ack revoked caps to mds as
@@ -1451,27 +1486,19 @@ void ceph_check_caps(struct ceph_inode_info *ci, int flags,
 	    (file_wanted == 0 ||                     /* no open files */
 	     (revoking & CEPH_CAP_FILE_CACHE)) &&     /*  or revoking cache */
 	    !tried_invalidate) {
-		u32 invalidating_gen = ci->i_rdcache_gen;
-		int ret;
-
 		dout("check_caps trying to invalidate on %p\n", inode);
-		spin_unlock(&inode->i_lock);
-		ret = invalidate_mapping_pages(&inode->i_data, 0, -1);
-		spin_lock(&inode->i_lock);
-		if (ret == 0 && invalidating_gen == ci->i_rdcache_gen) {
-			/* success. */
-			ci->i_rdcache_gen = 0;
-			ci->i_rdcache_revoking = 0;
-		} else if (revoking & CEPH_CAP_FILE_CACHE) {
-			dout("check_caps queuing invalidate\n");
-			queue_invalidate = 1;
-			ci->i_rdcache_revoking = ci->i_rdcache_gen;
-		} else {
-			dout("check_caps failed to invalidate pages\n");
-			/* we failed to invalidate pages.  check these
-			   caps again later. */
-			force_requeue = 1;
-			__cap_set_timeouts(mdsc, ci);
+		if (try_nonblocking_invalidate(inode) < 0) {
+			if (revoking & CEPH_CAP_FILE_CACHE) {
+				dout("check_caps queuing invalidate\n");
+				queue_invalidate = 1;
+				ci->i_rdcache_revoking = ci->i_rdcache_gen;
+			} else {
+				dout("check_caps failed to invalidate pages\n");
+				/* we failed to invalidate pages.  check these
+				   caps again later. */
+				force_requeue = 1;
+				__cap_set_timeouts(mdsc, ci);
+			}
 		}
 		tried_invalidate = 1;
 		goto retry_locked;
@@ -2184,7 +2211,6 @@ static int handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
 	int revoked_rdcache = 0;
 	int queue_invalidate = 0;
 	int tried_invalidate = 0;
-	int ret;
 
 	dout("handle_cap_grant inode %p cap %p mds%d seq %d %s\n",
 	     inode, cap, mds, seq, ceph_cap_string(newcaps));
@@ -2199,24 +2225,16 @@ static int handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
 restart:
 	if (((cap->issued & ~newcaps) & CEPH_CAP_FILE_CACHE) &&
 	    !ci->i_wrbuffer_ref && !tried_invalidate) {
-		dout("CACHE invalidation\n");
-		spin_unlock(&inode->i_lock);
 		tried_invalidate = 1;
-
-		ret = invalidate_mapping_pages(&inode->i_data, 0, -1);
-		spin_lock(&inode->i_lock);
-		if (ret < 0) {
+		if (try_nonblocking_invalidate(inode) == 0) {
+			revoked_rdcache = 1;
+		} else {
 			/* there were locked pages.. invalidate later
 			   in a separate thread. */
 			if (ci->i_rdcache_revoking != ci->i_rdcache_gen) {
 				queue_invalidate = 1;
 				ci->i_rdcache_revoking = ci->i_rdcache_gen;
 			}
-		} else {
-			/* we successfully invalidated those pages */
-			revoked_rdcache = 1;
-			ci->i_rdcache_gen = 0;
-			ci->i_rdcache_revoking = 0;
 		}
 		goto restart;
 	}