Merge tag 'for-hubcap-v4.9-readahead' of git://github.com/martinbrandenburg/linux

orangefs: integrate readahead cache changes from out-of-tree

The readahead cache has long been present as a compile time option to
OrangeFS. As it had not been tested in some time, it was disabled by
default. Recently, Walt Ligon started work reviving it, which eventually
culminated in the commit below to OrangeFS SVN.

r12519 | walt | 2016-07-13 14:32:42 -0400 (Wed, 13 Jul 2016) | 1 line
reintegrating readahead cache code

This cache is implemented almost entirely in userspace. There are a few
parameters exposed via sysfs, and the cache must be flushed after an
inode is released.

1 files changed, 62 insertions, 0 deletions

diff --git a/include/linux/ceph/string_table.h b/include/linux/ceph/string_table.h
new file mode 100644
index 000000000000..1b02c96daf75
--- /dev/null
+++ b/include/linux/ceph/string_table.h
@@ -0,0 +1,62 @@
+#ifndef _FS_CEPH_STRING_TABLE_H
+#define _FS_CEPH_STRING_TABLE_H
+
+#include <linux/types.h>
+#include <linux/kref.h>
+#include <linux/rbtree.h>
+#include <linux/rcupdate.h>
+
+struct ceph_string {
+	struct kref kref;
+	union {
+		struct rb_node node;
+		struct rcu_head rcu;
+	};
+	size_t len;
+	char str[];
+};
+
+extern void ceph_release_string(struct kref *ref);
+extern struct ceph_string *ceph_find_or_create_string(const char *str,
+						      size_t len);
+extern bool ceph_strings_empty(void);
+
+static inline struct ceph_string *ceph_get_string(struct ceph_string *str)
+{
+	kref_get(&str->kref);
+	return str;
+}
+
+static inline void ceph_put_string(struct ceph_string *str)
+{
+	if (!str)
+		return;
+	kref_put(&str->kref, ceph_release_string);
+}
+
+static inline int ceph_compare_string(struct ceph_string *cs,
+				      const char* str, size_t len)
+{
+	size_t cs_len = cs ? cs->len : 0;
+	if (cs_len != len)
+		return cs_len - len;
+	if (len == 0)
+		return 0;
+	return strncmp(cs->str, str, len);
+}
+
+#define ceph_try_get_string(x)					\
+({								\
+	struct ceph_string *___str;				\
+	rcu_read_lock();					\
+	for (;;) {						\
+		___str = rcu_dereference(x);			\
+		if (!___str ||					\
+		    kref_get_unless_zero(&___str->kref))	\
+			break;					\
+	}							\
+	rcu_read_unlock();					\
+	(___str);						\
+})
+
+#endif