fscache: Use refcount_t for the cookie refcount instead of atomic_t

Use refcount_t for the fscache_cookie refcount instead of atomic_t and
rename the 'usage' member to 'ref' in such cases.  The tracepoints that
reference it change from showing "u=%d" to "r=%d".

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/162431204358.2908479.8006938388213098079.stgit@warthog.procyon.org.uk/

diff --git a/fs/fscache/cache.c b/fs/fscache/cache.c
index e7a5d7a..bd4f44c 100644 (file)
--- a/fs/fscache/cache.c
+++ b/fs/fscache/cache.c
@@ -269,7 +269,7 @@ int fscache_add_cache(struct fscache_cache *cache,
        hlist_add_head(&ifsdef->cookie_link,
                       &fscache_fsdef_index.backing_objects);
 
-       atomic_inc(&fscache_fsdef_index.usage);
+       refcount_inc(&fscache_fsdef_index.ref);
 
        /* done */
        spin_unlock(&fscache_fsdef_index.lock);

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 6df3732..cd42be6 100644 (file)
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -164,7 +164,7 @@ struct fscache_cookie *fscache_alloc_cookie(
                        goto nomem;
        }
 
-       atomic_set(&cookie->usage, 1);
+       refcount_set(&cookie->ref, 1);
        atomic_set(&cookie->n_children, 0);
        cookie->debug_id = atomic_inc_return(&fscache_cookie_debug_id);
 
@@ -225,7 +225,7 @@ struct fscache_cookie *fscache_hash_cookie(struct fscache_cookie *candidate)
 
 collision:
        if (test_and_set_bit(FSCACHE_COOKIE_ACQUIRED, &cursor->flags)) {
-               trace_fscache_cookie(cursor->debug_id, atomic_read(&cursor->usage),
+               trace_fscache_cookie(cursor->debug_id, refcount_read(&cursor->ref),
                                     fscache_cookie_collision);
                pr_err("Duplicate cookie detected\n");
                fscache_print_cookie(cursor, 'O');
@@ -826,13 +826,12 @@ void __fscache_relinquish_cookie(struct fscache_cookie *cookie,
        BUG_ON(!radix_tree_empty(&cookie->stores));
 
        if (cookie->parent) {
-               ASSERTCMP(atomic_read(&cookie->parent->usage), >, 0);
+               ASSERTCMP(refcount_read(&cookie->parent->ref), >, 0);
                ASSERTCMP(atomic_read(&cookie->parent->n_children), >, 0);
                atomic_dec(&cookie->parent->n_children);
        }
 
        /* Dispose of the netfs's link to the cookie */
-       ASSERTCMP(atomic_read(&cookie->usage), >, 0);
        fscache_cookie_put(cookie, fscache_cookie_put_relinquish);
 
        _leave("");
@@ -862,18 +861,17 @@ void fscache_cookie_put(struct fscache_cookie *cookie,
                        enum fscache_cookie_trace where)
 {
        struct fscache_cookie *parent;
-       int usage;
+       int ref;
 
        _enter("%x", cookie->debug_id);
 
        do {
                unsigned int cookie_debug_id = cookie->debug_id;
-               usage = atomic_dec_return(&cookie->usage);
-               trace_fscache_cookie(cookie_debug_id, usage, where);
+               bool zero = __refcount_dec_and_test(&cookie->ref, &ref);
 
-               if (usage > 0)
+               trace_fscache_cookie(cookie_debug_id, ref - 1, where);
+               if (!zero)
                        return;
-               BUG_ON(usage < 0);
 
                parent = cookie->parent;
                fscache_unhash_cookie(cookie);
@@ -886,6 +884,19 @@ void fscache_cookie_put(struct fscache_cookie *cookie,
        _leave("");
 }
 
+/*
+ * Get a reference to a cookie.
+ */
+struct fscache_cookie *fscache_cookie_get(struct fscache_cookie *cookie,
+                                         enum fscache_cookie_trace where)
+{
+       int ref;
+
+       __refcount_inc(&cookie->ref, &ref);
+       trace_fscache_cookie(cookie->debug_id, ref + 1, where);
+       return cookie;
+}
+
 /*
  * check the consistency between the netfs inode and the backing cache
  *
@@ -1003,7 +1014,7 @@ static int fscache_cookies_seq_show(struct seq_file *m, void *v)
                   "%08x %08x %5u %5u %3u %s %03lx %-16s %px",
                   cookie->debug_id,
                   cookie->parent ? cookie->parent->debug_id : 0,
-                  atomic_read(&cookie->usage),
+                  refcount_read(&cookie->ref),
                   atomic_read(&cookie->n_children),
                   atomic_read(&cookie->n_active),
                   type,

diff --git a/fs/fscache/fsdef.c b/fs/fscache/fsdef.c
index 5f8f6fe..0402673 100644 (file)
--- a/fs/fscache/fsdef.c
+++ b/fs/fscache/fsdef.c
@@ -46,7 +46,7 @@ static struct fscache_cookie_def fscache_fsdef_index_def = {
 
 struct fscache_cookie fscache_fsdef_index = {
        .debug_id       = 1,
-       .usage          = ATOMIC_INIT(1),
+       .ref            = REFCOUNT_INIT(1),
        .n_active       = ATOMIC_INIT(1),
        .lock           = __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
        .backing_objects = HLIST_HEAD_INIT,

diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 345105d..c3e4804 100644 (file)
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -54,9 +54,18 @@ extern struct fscache_cookie *fscache_alloc_cookie(struct fscache_cookie *,
                                                   const void *, size_t,
                                                   void *, loff_t);
 extern struct fscache_cookie *fscache_hash_cookie(struct fscache_cookie *);
+extern struct fscache_cookie *fscache_cookie_get(struct fscache_cookie *,
+                                                enum fscache_cookie_trace);
 extern void fscache_cookie_put(struct fscache_cookie *,
                               enum fscache_cookie_trace);
 
+static inline void fscache_cookie_see(struct fscache_cookie *cookie,
+                                     enum fscache_cookie_trace where)
+{
+       trace_fscache_cookie(cookie->debug_id, refcount_read(&cookie->ref),
+                            where);
+}
+
 /*
  * fsdef.c
  */
@@ -286,14 +295,6 @@ static inline void fscache_raise_event(struct fscache_object *object,
                fscache_enqueue_object(object);
 }
 
-static inline void fscache_cookie_get(struct fscache_cookie *cookie,
-                                     enum fscache_cookie_trace where)
-{
-       int usage = atomic_inc_return(&cookie->usage);
-
-       trace_fscache_cookie(cookie->debug_id, usage, where);
-}
-
 /*
  * get an extra reference to a netfs retrieval context
  */

diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index ea61e54..a4dab59 100644 (file)
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -123,7 +123,7 @@ struct fscache_netfs {
  * - indices are created on disk just-in-time
  */
 struct fscache_cookie {
-       atomic_t                        usage;          /* number of users of this cookie */
+       refcount_t                      ref;            /* number of users of this cookie */
        atomic_t                        n_children;     /* number of children of this cookie */
        atomic_t                        n_active;       /* number of active users of netfs ptrs */
        unsigned int                    debug_id;

diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h
index 19d65d9..446392f 100644 (file)
--- a/include/trace/events/fscache.h
+++ b/include/trace/events/fscache.h
@@ -161,26 +161,26 @@ fscache_cookie_traces;
 
 TRACE_EVENT(fscache_cookie,
            TP_PROTO(unsigned int cookie_debug_id,
-                    int usage,
+                    int ref,
                     enum fscache_cookie_trace where),
 
-           TP_ARGS(cookie_debug_id, usage, where),
+           TP_ARGS(cookie_debug_id, ref, where),
 
            TP_STRUCT__entry(
                    __field(unsigned int,               cookie          )
                    __field(enum fscache_cookie_trace,  where           )
-                   __field(int,                        usage           )
+                   __field(int,                        ref             )
                             ),
 
            TP_fast_assign(
                    __entry->cookie     = cookie_debug_id;
                    __entry->where      = where;
-                   __entry->usage      = usage;
+                   __entry->ref        = ref;
                           ),
 
-           TP_printk("%s c=%08x u=%d",
+           TP_printk("%s c=%08x r=%d",
                      __print_symbolic(__entry->where, fscache_cookie_traces),
-                     __entry->cookie, __entry->usage)
+                     __entry->cookie, __entry->ref)
            );
 
 TRACE_EVENT(fscache_netfs,
@@ -212,7 +212,7 @@ TRACE_EVENT(fscache_acquire,
                    __field(unsigned int,               cookie          )
                    __field(unsigned int,               parent          )
                    __array(char,                       name, 8         )
-                   __field(int,                        p_usage         )
+                   __field(int,                        p_ref           )
                    __field(int,                        p_n_children    )
                    __field(u8,                         p_flags         )
                             ),
@@ -220,15 +220,15 @@ TRACE_EVENT(fscache_acquire,
            TP_fast_assign(
                    __entry->cookie             = cookie->debug_id;
                    __entry->parent             = cookie->parent->debug_id;
-                   __entry->p_usage            = atomic_read(&cookie->parent->usage);
+                   __entry->p_ref              = refcount_read(&cookie->parent->ref);
                    __entry->p_n_children       = atomic_read(&cookie->parent->n_children);
                    __entry->p_flags            = cookie->parent->flags;
                    memcpy(__entry->name, cookie->def->name, 8);
                    __entry->name[7]            = 0;
                           ),
 
-           TP_printk("c=%08x p=%08x pu=%d pc=%d pf=%02x n=%s",
-                     __entry->cookie, __entry->parent, __entry->p_usage,
+           TP_printk("c=%08x p=%08x pr=%d pc=%d pf=%02x n=%s",
+                     __entry->cookie, __entry->parent, __entry->p_ref,
                      __entry->p_n_children, __entry->p_flags, __entry->name)
            );
 
@@ -240,7 +240,7 @@ TRACE_EVENT(fscache_relinquish,
            TP_STRUCT__entry(
                    __field(unsigned int,               cookie          )
                    __field(unsigned int,               parent          )
-                   __field(int,                        usage           )
+                   __field(int,                        ref             )
                    __field(int,                        n_children      )
                    __field(int,                        n_active        )
                    __field(u8,                         flags           )
@@ -250,15 +250,15 @@ TRACE_EVENT(fscache_relinquish,
            TP_fast_assign(
                    __entry->cookie     = cookie->debug_id;
                    __entry->parent     = cookie->parent->debug_id;
-                   __entry->usage      = atomic_read(&cookie->usage);
+                   __entry->ref        = refcount_read(&cookie->ref);
                    __entry->n_children = atomic_read(&cookie->n_children);
                    __entry->n_active   = atomic_read(&cookie->n_active);
                    __entry->flags      = cookie->flags;
                    __entry->retire     = retire;
                           ),
 
-           TP_printk("c=%08x u=%d p=%08x Nc=%d Na=%d f=%02x r=%u",
-                     __entry->cookie, __entry->usage,
+           TP_printk("c=%08x r=%d p=%08x Nc=%d Na=%d f=%02x r=%u",
+                     __entry->cookie, __entry->ref,
                      __entry->parent, __entry->n_children, __entry->n_active,
                      __entry->flags, __entry->retire)
            );
@@ -270,7 +270,7 @@ TRACE_EVENT(fscache_enable,
 
            TP_STRUCT__entry(
                    __field(unsigned int,               cookie          )
-                   __field(int,                        usage           )
+                   __field(int,                        ref             )
                    __field(int,                        n_children      )
                    __field(int,                        n_active        )
                    __field(u8,                         flags           )
@@ -278,14 +278,14 @@ TRACE_EVENT(fscache_enable,
 
            TP_fast_assign(
                    __entry->cookie     = cookie->debug_id;
-                   __entry->usage      = atomic_read(&cookie->usage);
+                   __entry->ref        = refcount_read(&cookie->ref);
                    __entry->n_children = atomic_read(&cookie->n_children);
                    __entry->n_active   = atomic_read(&cookie->n_active);
                    __entry->flags      = cookie->flags;
                           ),
 
-           TP_printk("c=%08x u=%d Nc=%d Na=%d f=%02x",
-                     __entry->cookie, __entry->usage,
+           TP_printk("c=%08x r=%d Nc=%d Na=%d f=%02x",
+                     __entry->cookie, __entry->ref,
                      __entry->n_children, __entry->n_active, __entry->flags)
            );
 
@@ -296,7 +296,7 @@ TRACE_EVENT(fscache_disable,
 
            TP_STRUCT__entry(
                    __field(unsigned int,               cookie          )
-                   __field(int,                        usage           )
+                   __field(int,                        ref             )
                    __field(int,                        n_children      )
                    __field(int,                        n_active        )
                    __field(u8,                         flags           )
@@ -304,14 +304,14 @@ TRACE_EVENT(fscache_disable,
 
            TP_fast_assign(
                    __entry->cookie     = cookie->debug_id;
-                   __entry->usage      = atomic_read(&cookie->usage);
+                   __entry->ref        = refcount_read(&cookie->ref);
                    __entry->n_children = atomic_read(&cookie->n_children);
                    __entry->n_active   = atomic_read(&cookie->n_active);
                    __entry->flags      = cookie->flags;
                           ),
 
-           TP_printk("c=%08x u=%d Nc=%d Na=%d f=%02x",
-                     __entry->cookie, __entry->usage,
+           TP_printk("c=%08x r=%d Nc=%d Na=%d f=%02x",
+                     __entry->cookie, __entry->ref,
                      __entry->n_children, __entry->n_active, __entry->flags)
            );