Add a tracepoint to track fscache_use/unuse_cookie().
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: linux-cachefs@xxxxxxxxxx
---
fs/fscache/cookie.c | 29 +++++++++++++++++++++++---
include/trace/events/fscache.h | 44 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 69 insertions(+), 4 deletions(-)
diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index a7ea7d1db032..9bb1ab5fe5ed 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -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);
@@ -638,13 +643,29 @@ 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)) {
- fscache_unuse_cookie_locked(cookie);
- spin_unlock(&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);
diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h
index 1594aefadeac..cb3fb337e880 100644
--- a/include/trace/events/fscache.h
+++ b/include/trace/events/fscache.h
@@ -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,
--
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