FS-Cache: Provide proper invalidation

Provide a proper invalidation method rather than relying on the netfs retiring
the cookie it has and getting a new one.  The problem with this is that isn't
easy for the netfs to make sure that it has completed/cancelled all its
outstanding storage and retrieval operations on the cookie it is retiring.

Instead, have the cache provide an invalidation method that will cancel or wait
for all currently outstanding operations before invalidating the cache, and
will cause new operations to queue up behind that.  Whilst invalidation is in
progress, some requests will be rejected until the cache can stack a barrier on
the operation queue to cause new operations to be deferred behind it.

Signed-off-by: David Howells <dhowells@redhat.com>

2 files changed, 45 insertions, 1 deletions

diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index f5facd1d333f..1e454ad7a832 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -254,6 +254,9 @@ struct fscache_cache_ops {
         /* store the updated auxiliary data on an object */
         void (*update_object)(struct fscache_object *object);
 
+        /* Invalidate an object */
+        void (*invalidate_object)(struct fscache_operation *op);
+
         /* discard the resources pinned by an object and effect retirement if
          * necessary */
         void (*drop_object)(struct fscache_object *object);
@@ -329,6 +332,7 @@ struct fscache_cookie {
 #define FSCACHE_COOKIE_FILLING          4       /* T if filling object incrementally */
 #define FSCACHE_COOKIE_UNAVAILABLE      5       /* T if cookie is unavailable (error, etc) */
 #define FSCACHE_COOKIE_WAITING_ON_READS 6       /* T if cookie is waiting on reads */
+#define FSCACHE_COOKIE_INVALIDATING     7       /* T if cookie is being invalidated */
 };
 
 extern struct fscache_cookie fscache_fsdef_index;
@@ -345,6 +349,7 @@ struct fscache_object {
                 /* active states */
                 FSCACHE_OBJECT_AVAILABLE,       /* cleaning up object after creation */
                 FSCACHE_OBJECT_ACTIVE,          /* object is usable */
+                FSCACHE_OBJECT_INVALIDATING,    /* object is invalidating */
                 FSCACHE_OBJECT_UPDATING,        /* object is updating */
 
                 /* terminal states */
@@ -378,7 +383,8 @@ struct fscache_object {
 #define FSCACHE_OBJECT_EV_RELEASE       4       /* T if netfs requested object release */
 #define FSCACHE_OBJECT_EV_RETIRE        5       /* T if netfs requested object retirement */
 #define FSCACHE_OBJECT_EV_WITHDRAW      6       /* T if cache requested object withdrawal */
-#define FSCACHE_OBJECT_EVENTS_MASK      0x7f    /* mask of all events*/
+#define FSCACHE_OBJECT_EV_INVALIDATE    7       /* T if cache requested object invalidation */
+#define FSCACHE_OBJECT_EVENTS_MASK      0xff    /* mask of all events*/
 
         unsigned long           flags;
 #define FSCACHE_OBJECT_LOCK             0       /* T if object is busy being processed */
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index f4b6353543bf..7a086235da4b 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -185,6 +185,8 @@ extern struct fscache_cookie *__fscache_acquire_cookie(
 extern void __fscache_relinquish_cookie(struct fscache_cookie *, int);
 extern void __fscache_update_cookie(struct fscache_cookie *);
 extern int __fscache_attr_changed(struct fscache_cookie *);
+extern void __fscache_invalidate(struct fscache_cookie *);
+extern void __fscache_wait_on_invalidate(struct fscache_cookie *);
 extern int __fscache_read_or_alloc_page(struct fscache_cookie *,
                                         struct page *,
                                         fscache_rw_complete_t,
@@ -390,6 +392,42 @@ int fscache_attr_changed(struct fscache_cookie *cookie)
 }
 
 /**
+ * fscache_invalidate - Notify cache that an object needs invalidation
+ * @cookie: The cookie representing the cache object
+ *
+ * Notify the cache that an object is needs to be invalidated and that it
+ * should abort any retrievals or stores it is doing on the cache.  The object
+ * is then marked non-caching until such time as the invalidation is complete.
+ *
+ * This can be called with spinlocks held.
+ *
+ * See Documentation/filesystems/caching/netfs-api.txt for a complete
+ * description.
+ */
+static inline
+void fscache_invalidate(struct fscache_cookie *cookie)
+{
+        if (fscache_cookie_valid(cookie))
+                __fscache_invalidate(cookie);
+}
+
+/**
+ * fscache_wait_on_invalidate - Wait for invalidation to complete
+ * @cookie: The cookie representing the cache object
+ *
+ * Wait for the invalidation of an object to complete.
+ *
+ * See Documentation/filesystems/caching/netfs-api.txt for a complete
+ * description.
+ */
+static inline
+void fscache_wait_on_invalidate(struct fscache_cookie *cookie)
+{
+        if (fscache_cookie_valid(cookie))
+                __fscache_wait_on_invalidate(cookie);
+}
+
+/**
  * fscache_reserve_space - Reserve data space for a cached object
  * @cookie: The cookie representing the cache object
  * @i_size: The amount of space to be reserved