FS-Cache: Make cookie relinquishment wait for outstanding reads

Make fscache_relinquish_cookie() log a warning and wait if there are any
outstanding reads left on the cookie it was given.

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

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 0666996..66be9ec 100644 (file)
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -442,22 +442,32 @@ void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 
        event = retire ? FSCACHE_OBJECT_EV_RETIRE : FSCACHE_OBJECT_EV_RELEASE;
 
+try_again:
        spin_lock(&cookie->lock);
 
        /* break links with all the active objects */
        while (!hlist_empty(&cookie->backing_objects)) {
+               int n_reads;
                object = hlist_entry(cookie->backing_objects.first,
                                     struct fscache_object,
                                     cookie_link);
 
                _debug("RELEASE OBJ%x", object->debug_id);
 
-               if (atomic_read(&object->n_reads)) {
+               set_bit(FSCACHE_COOKIE_WAITING_ON_READS, &cookie->flags);
+               n_reads = atomic_read(&object->n_reads);
+               if (n_reads) {
+                       int n_ops = object->n_ops;
+                       int n_in_progress = object->n_in_progress;
                        spin_unlock(&cookie->lock);
                        printk(KERN_ERR "FS-Cache:"
-                              " Cookie '%s' still has %d outstanding reads\n",
-                              cookie->def->name, atomic_read(&object->n_reads));
-                       BUG();
+                              " Cookie '%s' still has %d outstanding reads (%d,%d)\n",
+                              cookie->def->name,
+                              n_reads, n_ops, n_in_progress);
+                       wait_on_bit(&cookie->flags, FSCACHE_COOKIE_WAITING_ON_READS,
+                                   fscache_wait_bit, TASK_UNINTERRUPTIBLE);
+                       printk("Wait finished\n");
+                       goto try_again;
                }
 
                /* detach each cache object from the object cookie */

diff --git a/fs/fscache/operation.c b/fs/fscache/operation.c
index 30afdfa..c857ab8 100644 (file)
--- a/fs/fscache/operation.c
+++ b/fs/fscache/operation.c
@@ -340,8 +340,14 @@ void fscache_put_operation(struct fscache_operation *op)
 
        object = op->object;
 
-       if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
-               atomic_dec(&object->n_reads);
+       if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags)) {
+               if (atomic_dec_and_test(&object->n_reads)) {
+                       clear_bit(FSCACHE_COOKIE_WAITING_ON_READS,
+                                 &object->cookie->flags);
+                       wake_up_bit(&object->cookie->flags,
+                                   FSCACHE_COOKIE_WAITING_ON_READS);
+               }
+       }
 
        /* now... we may get called with the object spinlock held, so we
         * complete the cleanup here only if we can immediately acquire the

diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index 9879183..e3d6d93 100644 (file)
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -301,6 +301,7 @@ struct fscache_cookie {
 #define FSCACHE_COOKIE_PENDING_FILL    3       /* T if pending initial fill on object */
 #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 */
 };
 
 extern struct fscache_cookie fscache_fsdef_index;