Commit e6435f1e authored by David Howells's avatar David Howells
Browse files

fscache: Add a tracepoint for cookie use/unuse 



Add a tracepoint to track fscache_use/unuse_cookie().

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/164021588628.640689.12942919367404043608.stgit@warthog.procyon.org.uk/ # v4
parent e0484344

fs/fscache/cookie.c

+25 −4
Original line number Diff line number Diff line
@@ -556,6 +556,7 @@ void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify) 
{

	enum fscache_cookie_state state;

	bool queue = false;

	int n_active;



	_enter("c=%08x", cookie->debug_id);
@@ -565,7 +566,11 @@ void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify) 


	spin_lock(&cookie->lock);



	atomic_inc(&cookie->n_active);

	n_active = atomic_inc_return(&cookie->n_active);

	trace_fscache_active(cookie->debug_id, refcount_read(&cookie->ref),

			     n_active, atomic_read(&cookie->n_accesses),

			     will_modify ?

			     fscache_active_use_modify : fscache_active_use);



again:

	state = fscache_cookie_state(cookie);
@@ -638,14 +643,30 @@ static void fscache_unuse_cookie_locked(struct fscache_cookie *cookie) 
void __fscache_unuse_cookie(struct fscache_cookie *cookie,

			    const void *aux_data, const loff_t *object_size)

{

	unsigned int debug_id = cookie->debug_id;

	unsigned int r = refcount_read(&cookie->ref);

	unsigned int a = atomic_read(&cookie->n_accesses);

	unsigned int c;



	if (aux_data || object_size)

		__fscache_update_cookie(cookie, aux_data, object_size);



	if (atomic_dec_and_lock(&cookie->n_active, &cookie->lock)) {

	/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */

	c = atomic_fetch_add_unless(&cookie->n_active, -1, 1);

	if (c != 1) {

		trace_fscache_active(debug_id, r, c - 1, a, fscache_active_unuse);

		return;

	}



	spin_lock(&cookie->lock);

	r = refcount_read(&cookie->ref);

	a = atomic_read(&cookie->n_accesses);

	c = atomic_dec_return(&cookie->n_active);

	trace_fscache_active(debug_id, r, c, a, fscache_active_unuse);

	if (c == 0)

		fscache_unuse_cookie_locked(cookie);

	spin_unlock(&cookie->lock);

}

}

EXPORT_SYMBOL(__fscache_unuse_cookie);



/*

include/trace/events/fscache.h

+44 −0
Original line number Diff line number Diff line
@@ -71,6 +71,12 @@ enum fscache_cookie_trace { 
	fscache_cookie_see_work,

};



enum fscache_active_trace {

	fscache_active_use,

	fscache_active_use_modify,

	fscache_active_unuse,

};



enum fscache_access_trace {

	fscache_access_acquire_volume,

	fscache_access_acquire_volume_end,
@@ -146,6 +152,11 @@ enum fscache_access_trace { 
	EM(fscache_cookie_see_withdraw,		"-   x-wth")		\

	E_(fscache_cookie_see_work,		"-   work ")



#define fscache_active_traces		\

	EM(fscache_active_use,			"USE          ")	\

	EM(fscache_active_use_modify,		"USE-m        ")	\

	E_(fscache_active_unuse,		"UNUSE        ")



#define fscache_access_traces		\

	EM(fscache_access_acquire_volume,	"BEGIN acq_vol")	\

	EM(fscache_access_acquire_volume_end,	"END   acq_vol")	\
@@ -264,6 +275,39 @@ TRACE_EVENT(fscache_cookie, 
		      __entry->ref)

	    );



TRACE_EVENT(fscache_active,

	    TP_PROTO(unsigned int cookie_debug_id,

		     int ref,

		     int n_active,

		     int n_accesses,

		     enum fscache_active_trace why),



	    TP_ARGS(cookie_debug_id, ref, n_active, n_accesses, why),



	    TP_STRUCT__entry(

		    __field(unsigned int,		cookie		)

		    __field(int,			ref		)

		    __field(int,			n_active	)

		    __field(int,			n_accesses	)

		    __field(enum fscache_active_trace,	why		)

			     ),



	    TP_fast_assign(

		    __entry->cookie	= cookie_debug_id;

		    __entry->ref	= ref;

		    __entry->n_active	= n_active;

		    __entry->n_accesses	= n_accesses;

		    __entry->why	= why;

			   ),



	    TP_printk("c=%08x %s r=%d a=%d c=%d",

		      __entry->cookie,

		      __print_symbolic(__entry->why, fscache_active_traces),

		      __entry->ref,

		      __entry->n_accesses,

		      __entry->n_active)

	    );



TRACE_EVENT(fscache_access_cache,

	    TP_PROTO(unsigned int cache_debug_id,

		     int ref,