CacheFiles: Catch an overly long wait for an old active object

[safe/jmp/linux-2.6] / fs / cachefiles / namei.c

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 00a0cda..14ac480 100644 (file)
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -21,12 +21,6 @@
 #include <linux/security.h>
 #include "internal.h"
 
-static int cachefiles_wait_bit(void *flags)
-{
-       schedule();
-       return 0;
-}
-
 #define CACHEFILES_KEYBUF_SIZE 512
 
 /*
@@ -100,8 +94,8 @@ static noinline void cachefiles_printk_object(struct cachefiles_object *object,
 /*
  * record the fact that an object is now active
  */
-static void cachefiles_mark_object_active(struct cachefiles_cache *cache,
-                                         struct cachefiles_object *object)
+static int cachefiles_mark_object_active(struct cachefiles_cache *cache,
+                                        struct cachefiles_object *object)
 {
        struct cachefiles_object *xobject;
        struct rb_node **_p, *_parent = NULL;
@@ -139,8 +133,8 @@ try_again:
        rb_insert_color(&object->active_node, &cache->active_nodes);
 
        write_unlock(&cache->active_lock);
-       _leave("");
-       return;
+       _leave(" = 0");
+       return 0;
 
        /* an old object from a previous incarnation is hogging the slot - we
         * need to wait for it to be destroyed */
@@ -155,13 +149,64 @@ wait_for_old_object:
        atomic_inc(&xobject->usage);
        write_unlock(&cache->active_lock);
 
-       _debug(">>> wait");
-       wait_on_bit(&xobject->flags, CACHEFILES_OBJECT_ACTIVE,
-                   cachefiles_wait_bit, TASK_UNINTERRUPTIBLE);
-       _debug("<<< waited");
+       if (test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags)) {
+               wait_queue_head_t *wq;
+
+               signed long timeout = 60 * HZ;
+               wait_queue_t wait;
+               bool requeue;
+
+               /* if the object we're waiting for is queued for processing,
+                * then just put ourselves on the queue behind it */
+               if (slow_work_is_queued(&xobject->fscache.work)) {
+                       _debug("queue OBJ%x behind OBJ%x immediately",
+                              object->fscache.debug_id,
+                              xobject->fscache.debug_id);
+                       goto requeue;
+               }
+
+               /* otherwise we sleep until either the object we're waiting for
+                * is done, or the slow-work facility wants the thread back to
+                * do other work */
+               wq = bit_waitqueue(&xobject->flags, CACHEFILES_OBJECT_ACTIVE);
+               init_wait(&wait);
+               requeue = false;
+               do {
+                       prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
+                       if (!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags))
+                               break;
+                       requeue = slow_work_sleep_till_thread_needed(
+                               &object->fscache.work, &timeout);
+               } while (timeout > 0 && !requeue);
+               finish_wait(wq, &wait);
+
+               if (requeue &&
+                   test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags)) {
+                       _debug("queue OBJ%x behind OBJ%x after wait",
+                              object->fscache.debug_id,
+                              xobject->fscache.debug_id);
+                       goto requeue;
+               }
+
+               if (timeout <= 0) {
+                       printk(KERN_ERR "\n");
+                       printk(KERN_ERR "CacheFiles: Error: Overlong"
+                              " wait for old active object to go away\n");
+                       cachefiles_printk_object(object, xobject);
+                       goto requeue;
+               }
+       }
+
+       ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags));
 
        cache->cache.ops->put_object(&xobject->fscache);
        goto try_again;
+
+requeue:
+       clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
+       cache->cache.ops->put_object(&xobject->fscache);
+       _leave(" = -ETIMEDOUT");
+       return -ETIMEDOUT;
 }
 
 /*
@@ -466,12 +511,15 @@ lookup_again:
        }
 
        /* note that we're now using this object */
-       cachefiles_mark_object_active(cache, object);
+       ret = cachefiles_mark_object_active(cache, object);
 
        mutex_unlock(&dir->d_inode->i_mutex);
        dput(dir);
        dir = NULL;
 
+       if (ret == -ETIMEDOUT)
+               goto mark_active_timed_out;
+
        _debug("=== OBTAINED_OBJECT ===");
 
        if (object->new) {
@@ -515,6 +563,10 @@ create_error:
                cachefiles_io_error(cache, "Create/mkdir failed");
        goto error;
 
+mark_active_timed_out:
+       _debug("mark active timed out");
+       goto release_dentry;
+
 check_error:
        _debug("check error %d", ret);
        write_lock(&cache->active_lock);
@@ -522,7 +574,7 @@ check_error:
        clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
        wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE);
        write_unlock(&cache->active_lock);
-
+release_dentry:
        dput(object->dentry);
        object->dentry = NULL;
        goto error_out;
@@ -543,9 +595,6 @@ error:
 error_out2:
        dput(dir);
 error_out:
-       if (ret == -ENOSPC)
-               ret = -ENOBUFS;
-
        _leave(" = error %d", -ret);
        return ret;
 }