7 files changed, 90 insertions, 25 deletions

diff --git a/Documentation/filesystems/caching/fscache.txt b/Documentation/filesystems/caching/fscache.txt
index 3c23411956bb..a91e2e2095b0 100644
--- a/Documentation/filesystems/caching/fscache.txt
+++ b/Documentation/filesystems/caching/fscache.txt
@@ -235,6 +235,7 @@ proc files.
                 neg=N   Number of negative lookups made
                 pos=N   Number of positive lookups made
                 crt=N   Number of objects created by lookup
+                tmo=N   Number of lookups timed out and requeued
         Updates n=N     Number of update cookie requests seen
                 nul=N   Number of upd reqs given a NULL parent
                 run=N   Number of upd reqs granted CPU time
diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index 8e67abf05985..9d3c426044ae 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -114,8 +114,9 @@ nomem_lookup_data:
 
 /*
  * attempt to look up the nominated node in this cache
+ * - return -ETIMEDOUT to be scheduled again
  */
-static void cachefiles_lookup_object(struct fscache_object *_object)
+static int cachefiles_lookup_object(struct fscache_object *_object)
 {
         struct cachefiles_lookup_data *lookup_data;
         struct cachefiles_object *parent, *object;
@@ -145,13 +146,14 @@ static void cachefiles_lookup_object(struct fscache_object *_object)
             object->fscache.cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX)
                 cachefiles_attr_changed(&object->fscache);
 
-        if (ret < 0) {
+        if (ret < 0 && ret != -ETIMEDOUT) {
                 printk(KERN_WARNING "CacheFiles: Lookup failed error %d\n",
                        ret);
                 fscache_object_lookup_error(&object->fscache);
         }
 
         _leave(" [%d]", ret);
+        return ret;
 }
 
 /*
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 00a0cda8f47a..14ac4806e291 100644
--- 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;
 }
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 5b49a373689b..0ca2566e038c 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -215,6 +215,7 @@ extern atomic_t fscache_n_object_no_alloc;
 extern atomic_t fscache_n_object_lookups;
 extern atomic_t fscache_n_object_lookups_negative;
 extern atomic_t fscache_n_object_lookups_positive;
+extern atomic_t fscache_n_object_lookups_timed_out;
 extern atomic_t fscache_n_object_created;
 extern atomic_t fscache_n_object_avail;
 extern atomic_t fscache_n_object_dead;
diff --git a/fs/fscache/object.c b/fs/fscache/object.c
index f3f952cf887e..e513ac599c8e 100644
--- a/fs/fscache/object.c
+++ b/fs/fscache/object.c
@@ -468,6 +468,7 @@ static void fscache_lookup_object(struct fscache_object *object)
 {
         struct fscache_cookie *cookie = object->cookie;
         struct fscache_object *parent;
+        int ret;
 
         _enter("");
 
@@ -493,12 +494,19 @@ static void fscache_lookup_object(struct fscache_object *object)
 
         fscache_stat(&fscache_n_object_lookups);
         fscache_stat(&fscache_n_cop_lookup_object);
-        object->cache->ops->lookup_object(object);
+        ret = object->cache->ops->lookup_object(object);
         fscache_stat_d(&fscache_n_cop_lookup_object);
 
         if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
                 set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 
+        if (ret == -ETIMEDOUT) {
+                /* probably stuck behind another object, so move this one to
+                 * the back of the queue */
+                fscache_stat(&fscache_n_object_lookups_timed_out);
+                set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
+        }
+
         _leave("");
 }
 
diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index 05f77caf4a2d..46435f3aae68 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -98,6 +98,7 @@ atomic_t fscache_n_object_no_alloc;
 atomic_t fscache_n_object_lookups;
 atomic_t fscache_n_object_lookups_negative;
 atomic_t fscache_n_object_lookups_positive;
+atomic_t fscache_n_object_lookups_timed_out;
 atomic_t fscache_n_object_created;
 atomic_t fscache_n_object_avail;
 atomic_t fscache_n_object_dead;
@@ -160,10 +161,11 @@ static int fscache_stats_show(struct seq_file *m, void *v)
                    atomic_read(&fscache_n_acquires_nobufs),
                    atomic_read(&fscache_n_acquires_oom));
 
-        seq_printf(m, "Lookups: n=%u neg=%u pos=%u crt=%u\n",
+        seq_printf(m, "Lookups: n=%u neg=%u pos=%u crt=%u tmo=%u\n",
                    atomic_read(&fscache_n_object_lookups),
                    atomic_read(&fscache_n_object_lookups_negative),
                    atomic_read(&fscache_n_object_lookups_positive),
+                   atomic_read(&fscache_n_object_lookups_timed_out),
                    atomic_read(&fscache_n_object_created));
 
         seq_printf(m, "Updates: n=%u nul=%u run=%u\n",
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index 5db50002f3b5..7be0c6fbe880 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -234,8 +234,10 @@ struct fscache_cache_ops {
         struct fscache_object *(*alloc_object)(struct fscache_cache *cache,
                                                struct fscache_cookie *cookie);
 
-        /* look up the object for a cookie */
-        void (*lookup_object)(struct fscache_object *object);
+        /* look up the object for a cookie
+         * - return -ETIMEDOUT to be requeued
+         */
+        int (*lookup_object)(struct fscache_object *object);
 
         /* finished looking up */
         void (*lookup_complete)(struct fscache_object *object);