fscache: Implement cache registration

Implement a register of caches and provide functions to manage it.

Two functions are provided for the cache backend to use:

 (1) Acquire a cache cookie:

	struct fscache_cache *fscache_acquire_cache(const char *name)

     This gets the cache cookie for a cache of the specified name and moves
     it to the preparation state.  If a nameless cache cookie exists, that
     will be given this name and used.

 (2) Relinquish a cache cookie:

	void fscache_relinquish_cache(struct fscache_cache *cache);

     This relinquishes a cache cookie, cleans it and makes it available if
     it's still referenced by a network filesystem.

Note that network filesystems don't deal with cache cookies directly, but
rather go straight to the volume registration.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819587157.215744.13523139317322503286.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906889665.143852.10378009165231294456.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967085081.1823006.2218944206363626210.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021494847.640689.10109692261640524343.stgit@warthog.procyon.org.uk/ # v4

1 files changed, 43 insertions, 0 deletions

diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h
index fe214c5cc87f..3b8e0597b2c1 100644
--- a/include/trace/events/fscache.h
+++ b/include/trace/events/fscache.h
@@ -19,11 +19,27 @@
 #ifndef __FSCACHE_DECLARE_TRACE_ENUMS_ONCE_ONLY
 #define __FSCACHE_DECLARE_TRACE_ENUMS_ONCE_ONLY
 
+enum fscache_cache_trace {
+	fscache_cache_collision,
+	fscache_cache_get_acquire,
+	fscache_cache_new_acquire,
+	fscache_cache_put_cache,
+	fscache_cache_put_prep_failed,
+	fscache_cache_put_relinquish,
+};
+
 #endif
 
 /*
  * Declare tracing information enums and their string mappings for display.
  */
+#define fscache_cache_traces						\
+	EM(fscache_cache_collision,		"*COLLIDE*")		\
+	EM(fscache_cache_get_acquire,		"GET acq  ")		\
+	EM(fscache_cache_new_acquire,		"NEW acq  ")		\
+	EM(fscache_cache_put_cache,		"PUT cache")		\
+	EM(fscache_cache_put_prep_failed,	"PUT pfail")		\
+	E_(fscache_cache_put_relinquish,	"PUT relnq")
 
 /*
  * Export enum symbols via userspace.
@@ -33,6 +49,8 @@
 #define EM(a, b) TRACE_DEFINE_ENUM(a);
 #define E_(a, b) TRACE_DEFINE_ENUM(a);
 
+fscache_cache_traces;
+
 /*
  * Now redefine the EM() and E_() macros to map the enums to the strings that
  * will be printed in the output.
@@ -43,6 +61,31 @@
 #define E_(a, b)	{ a, b }
 
 
+TRACE_EVENT(fscache_cache,
+	    TP_PROTO(unsigned int cache_debug_id,
+		     int usage,
+		     enum fscache_cache_trace where),
+
+	    TP_ARGS(cache_debug_id, usage, where),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned int,		cache		)
+		    __field(int,			usage		)
+		    __field(enum fscache_cache_trace,	where		)
+			     ),
+
+	    TP_fast_assign(
+		    __entry->cache	= cache_debug_id;
+		    __entry->usage	= usage;
+		    __entry->where	= where;
+			   ),
+
+	    TP_printk("C=%08x %s r=%d",
+		      __entry->cache,
+		      __print_symbolic(__entry->where, fscache_cache_traces),
+		      __entry->usage)
+	    );
+
 #endif /* _TRACE_FSCACHE_H */
 
 /* This part must be outside protection */